Topics

Total Resistance In The Synchronome?


Brian Cracknell
 

According to Mitchell's "Setting to Work" instructions the total resistance in the Synchronome is made up of of 8.7 ohms (main solenoid) and 2.45 ohms (pilot slave) giving around 11.15 ohms total. My Synchronome however (an early 1920s, apparently unfiddled-with one with the original green cotton still on the coils) seems to have a resistance of 7.00 ohms showing on the ohmmeter when the circuit is closed. This reading is also supported by the fact that my power supply shows 3.3 volts on the voltmeter and when I add a 3 ohm resistor (providing 10 ohms total resistance) I get the required 0.33 amp current showing on my ammeter.

So my question is, does anyone have a not-in-use Synchronome that can be checked to see what the resistance is on that?

And my other, key question: if it turns out that others do have the 11 ohms as Mitchell mentions, what can have happened to mine to make it be different? Looking at the wiring, one wire goes into the bottom coil and another wire comes out the top coil so they do both seem to be wired up.

Thanks
Brian


Ian Richardson
 

Brian,

I've no doubt that others will chip in on this one.  I wouldn't take too literally what Arthur wrote as there would be quite a variation in values due to manufacturing tolerances.  The nominal resistance values help establishing roughly what voltage will be required, but in the final analysis, it's the current flowing through the whole system (which includes the system wiring) which matters.  With remote slave dials, the inter-clock wiring could easily amount to several Ohms, making a mockery of your calculations!

Also note that there is hidden wire-wound resistor behind the movement plate which is shunted across the coils to act as a rudimentary spark quench.  Have you taken that into account?

Cheers,
Ian R
Macclesfield, UK



-----Original Message-----
From: Brian Cracknell <brcracknell@...>
To: synchronome1@groups.io
Sent: Mon, 29 Jun 2020 12:31
Subject: [synchronomeelectricclock] Total Resistance In The Synchronome?

According to Mitchell's "Setting to Work" instructions the total resistance in the Synchronome is made up of of 8.7 ohms (main solenoid) and 2.45 ohms (pilot slave) giving around 11.15 ohms total. My Synchronome however (an early 1920s, apparently unfiddled-with one with the original green cotton still on the coils) seems to have a resistance of 7.00 ohms showing on the ohmmeter when the circuit is closed. This reading is also supported by the fact that my power supply shows 3.3 volts on the voltmeter and when I add a 3 ohm resistor (providing 10 ohms total resistance) I get the required 0.33 amp current showing on my ammeter.

So my question is, does anyone have a not-in-use Synchronome that can be checked to see what the resistance is on that?

And my other, key question: if it turns out that others do have the 11 ohms as Mitchell mentions, what can have happened to mine to make it be different? Looking at the wiring, one wire goes into the bottom coil and another wire comes out the top coil so they do both seem to be wired up.

Thanks
Brian


H Hal
 

I will check mine when I get into the workshop.
 
In the mean time what jumps out for me is that your 7 ohms I presume is total resistance so your main solenoid has 7 minus 2.45= 4.55 ohms
 
now if one of the two main coils has failed (shorted) the main resistance would be half of 8.7 ie 4.35 with a little resistance from the shorted coil giving 4.55 ohms
 
 
in other words I would suspect one of the main coils to be wired incorrectly or shorted out
 
 
 
hal
 
uk
 

From: Brian Cracknell
Sent: Monday, June 29, 2020 11:31 AM
To: synchronome1@groups.io
Subject: [synchronomeelectricclock] Total Resistance In The Synchronome?
 
According to Mitchell's "Setting to Work" instructions the total resistance in the Synchronome is made up of of 8.7 ohms (main solenoid) and 2.45 ohms (pilot slave) giving around 11.15 ohms total. My Synchronome however (an early 1920s, apparently unfiddled-with one with the original green cotton still on the coils) seems to have a resistance of 7.00 ohms showing on the ohmmeter when the circuit is closed. This reading is also supported by the fact that my power supply shows 3.3 volts on the voltmeter and when I add a 3 ohm resistor (providing 10 ohms total resistance) I get the required 0.33 amp current showing on my ammeter.

So my question is, does anyone have a not-in-use Synchronome that can be checked to see what the resistance is on that?

And my other, key question: if it turns out that others do have the 11 ohms as Mitchell mentions, what can have happened to mine to make it be different? Looking at the wiring, one wire goes into the bottom coil and another wire comes out the top coil so they do both seem to be wired up.

Thanks
Brian


Brian Cracknell
 

Hal, Ian, thanks for the replies. I did think the maths worked out a bit suspiciously as if only one coil was connected but how do I go about proving the function of either coil? The tails of those coils look very delicate so I am a bit hesitant to start poking around too much unless I have to. I would like to follow the wiring though but I am not sure what the flow of wires should be. The coils "input" wire from the bottom of the armature disappears under the lower coil and presumably connects into that wire-wound resistor that Ian mentioned which I can just see between the coils right at the back and then the flow must come back into the first coil again, thence to the second one - they are in series I take it? I can't seem to find a circuit diagram anywhere.

Both coils have two wires connected as far as I can make out in the tight space. If the bottom coil was broken I had assumed no current could flow through the whole circuit? (Unless it had been bypassed but I can not see that this is the case.)

By the way, the other movements I have looked at on the computer have the wire from the armature going into a hole through the movement plate below the lower coil, just above the armature return spring. My clock doesn't have that hole so presumably that was a change in design later on.

The clock works reasonably well but has never (in the 10 years I have owned it) kept time precisely. So I keep fiddling with it and this is just the latest anomaly I have noticed.

Brian


From: synchronome1@groups.io <synchronome1@groups.io> on behalf of H Hal via groups.io <haal@...>
Sent: 29 June 2020 13:23
To: synchronome1@groups.io <synchronome1@groups.io>
Subject: Re: [synchronomeelectricclock] Total Resistance In The Synchronome?
 
I will check mine when I get into the workshop.
 
In the mean time what jumps out for me is that your 7 ohms I presume is total resistance so your main solenoid has 7 minus 2.45= 4.55 ohms
 
now if one of the two main coils has failed (shorted) the main resistance would be half of 8.7 ie 4.35 with a little resistance from the shorted coil giving 4.55 ohms
 
 
in other words I would suspect one of the main coils to be wired incorrectly or shorted out
 
 
 
hal
 
uk
 
From: Brian Cracknell
Sent: Monday, June 29, 2020 11:31 AM
To: synchronome1@groups.io
Subject: [synchronomeelectricclock] Total Resistance In The Synchronome?
 
According to Mitchell's "Setting to Work" instructions the total resistance in the Synchronome is made up of of 8.7 ohms (main solenoid) and 2.45 ohms (pilot slave) giving around 11.15 ohms total. My Synchronome however (an early 1920s, apparently unfiddled-with one with the original green cotton still on the coils) seems to have a resistance of 7.00 ohms showing on the ohmmeter when the circuit is closed. This reading is also supported by the fact that my power supply shows 3.3 volts on the voltmeter and when I add a 3 ohm resistor (providing 10 ohms total resistance) I get the required 0.33 amp current showing on my ammeter.

So my question is, does anyone have a not-in-use Synchronome that can be checked to see what the resistance is on that?

And my other, key question: if it turns out that others do have the 11 ohms as Mitchell mentions, what can have happened to mine to make it be different? Looking at the wiring, one wire goes into the bottom coil and another wire comes out the top coil so they do both seem to be wired up.

Thanks
Brian


John Hubert
 

The coils are indeed connected in series - and the (one) resistor is in parallel with the two series coils.  Its value is roughly 10x that of the coils.

The coils are connected to the chassis at one end (the one that goes to the contact on the armature) and to the (lower on most clocks, but centre on clocks with three terminals) terminal screw, so measuring between that terminal and chassis should give the resistance of the combination of the two coils in series with the parallel resistor.  IF there is a short to chassis at the point where the coils join - then you would only measure the resistance of one coil.

The electrical side would not of course vary the timekeeping, which should be typically a very few seconds a week or better.


John Hubert





On 29 Jun 2020, at 14:55, Brian Cracknell <brcracknell@...> wrote:

Hal, Ian, thanks for the replies. I did think the maths worked out a bit suspiciously as if only one coil was connected but how do I go about proving the function of either coil? The tails of those coils look very delicate so I am a bit hesitant to start poking around too much unless I have to. I would like to follow the wiring though but I am not sure what the flow of wires should be. The coils "input" wire from the bottom of the armature disappears under the lower coil and presumably connects into that wire-wound resistor that Ian mentioned which I can just see between the coils right at the back and then the flow must come back into the first coil again, thence to the second one - they are in series I take it? I can't seem to find a circuit diagram anywhere.

Both coils have two wires connected as far as I can make out in the tight space. If the bottom coil was broken I had assumed no current could flow through the whole circuit? (Unless it had been bypassed but I can not see that this is the case.)

By the way, the other movements I have looked at on the computer have the wire from the armature going into a hole through the movement plate below the lower coil, just above the armature return spring. My clock doesn't have that hole so presumably that was a change in design later on.

The clock works reasonably well but has never (in the 10 years I have owned it) kept time precisely. So I keep fiddling with it and this is just the latest anomaly I have noticed.

Brian


From: synchronome1@groups.io <synchronome1@groups.io> on behalf of H Hal via groups.io <haal@...>
Sent: 29 June 2020 13:23
To: synchronome1@groups.io <synchronome1@groups.io>
Subject: Re: [synchronomeelectricclock] Total Resistance In The Synchronome?
 
I will check mine when I get into the workshop.
 
In the mean time what jumps out for me is that your 7 ohms I presume is total resistance so your main solenoid has 7 minus 2.45= 4.55 ohms
 
now if one of the two main coils has failed (shorted) the main resistance would be half of 8.7 ie 4.35 with a little resistance from the shorted coil giving 4.55 ohms
 
 
in other words I would suspect one of the main coils to be wired incorrectly or shorted out
 
 
 
hal
 
uk
 
From: Brian Cracknell
Sent: Monday, June 29, 2020 11:31 AM
Subject: [synchronomeelectricclock] Total Resistance In The Synchronome?
 
According to Mitchell's "Setting to Work" instructions the total resistance in the Synchronome is made up of of 8.7 ohms (main solenoid) and 2.45 ohms (pilot slave) giving around 11.15 ohms total. My Synchronome however (an early 1920s, apparently unfiddled-with one with the original green cotton still on the coils) seems to have a resistance of 7.00 ohms showing on the ohmmeter when the circuit is closed. This reading is also supported by the fact that my power supply shows 3.3 volts on the voltmeter and when I add a 3 ohm resistor (providing 10 ohms total resistance) I get the required 0.33 amp current showing on my ammeter.

So my question is, does anyone have a not-in-use Synchronome that can be checked to see what the resistance is on that?

And my other, key question: if it turns out that others do have the 11 ohms as Mitchell mentions, what can have happened to mine to make it be different? Looking at the wiring, one wire goes into the bottom coil and another wire comes out the top coil so they do both seem to be wired up.

Thanks
Brian 


H Hal
 

Brian,
 
In my experience you will find the problem, if indeed there is one by pulling the the thing apart.
 
Plenty of room to leave parts overnight
 
Lots of photos and drawings as you go
 
all screws, bolts, washers in the order you remove them and labelled if necessary in an ice cube holder or some such
 
as you take it apart, the coil connections/terminals willreveal themselves, measure resistance of individual coils to hunt down the problem
 
 
what you really need is an excuse to spend a fewdays on it without having to go to work.....hang on!
 
 
 
good luck
 
hal  uk
 
ps
 
I have never set up my clocks/systems measuring voltage.
If all electrical connections, coils, switches are “good” then I wire up and include an ammeter to monitor the current...of course you need to know roughly the voltage that will be required but if you have a reasonable power supply you can start from 0V and increase as you go...when all is good you can source a final power supply of slightly higher voltage you got to and tweak the current by adding extra resistance
 
 
 
hal
 
uk
 
 
 

From: Brian Cracknell
Sent: Monday, June 29, 2020 2:55 PM
To: synchronome1@groups.io
Subject: Re: [synchronomeelectricclock] Total Resistance In The Synchronome?
 
Hal, Ian, thanks for the replies. I did think the maths worked out a bit suspiciously as if only one coil was connected but how do I go about proving the function of either coil? The tails of those coils look very delicate so I am a bit hesitant to start poking around too much unless I have to. I would like to follow the wiring though but I am not sure what the flow of wires should be. The coils "input" wire from the bottom of the armature disappears under the lower coil and presumably connects into that wire-wound resistor that Ian mentioned which I can just see between the coils right at the back and then the flow must come back into the first coil again, thence to the second one - they are in series I take it? I can't seem to find a circuit diagram anywhere.
 
Both coils have two wires connected as far as I can make out in the tight space. If the bottom coil was broken I had assumed no current could flow through the whole circuit? (Unless it had been bypassed but I can not see that this is the case.)
 
By the way, the other movements I have looked at on the computer have the wire from the armature going into a hole through the movement plate below the lower coil, just above the armature return spring. My clock doesn't have that hole so presumably that was a change in design later on.
 
The clock works reasonably well but has never (in the 10 years I have owned it) kept time precisely. So I keep fiddling with it and this is just the latest anomaly I have noticed.
 
Brian
 

From: synchronome1@groups.io <synchronome1@groups.io> on behalf of H Hal via groups.io <haal@...>
Sent: 29 June 2020 13:23
To: synchronome1@groups.io <synchronome1@groups.io>
Subject: Re: [synchronomeelectricclock] Total Resistance In The Synchronome?
 
I will check mine when I get into the workshop.
 
In the mean time what jumps out for me is that your 7 ohms I presume is total resistance so your main solenoid has 7 minus 2.45= 4.55 ohms
 
now if one of the two main coils has failed (shorted) the main resistance would be half of 8.7 ie 4.35 with a little resistance from the shorted coil giving 4.55 ohms
 
 
in other words I would suspect one of the main coils to be wired incorrectly or shorted out
 
 
 
hal
 
uk
 
From: Brian Cracknell
Sent: Monday, June 29, 2020 11:31 AM
To: synchronome1@groups.io
Subject: [synchronomeelectricclock] Total Resistance In The Synchronome?
 
According to Mitchell's "Setting to Work" instructions the total resistance in the Synchronome is made up of of 8.7 ohms (main solenoid) and 2.45 ohms (pilot slave) giving around 11.15 ohms total. My Synchronome however (an early 1920s, apparently unfiddled-with one with the original green cotton still on the coils) seems to have a resistance of 7.00 ohms showing on the ohmmeter when the circuit is closed. This reading is also supported by the fact that my power supply shows 3.3 volts on the voltmeter and when I add a 3 ohm resistor (providing 10 ohms total resistance) I get the required 0.33 amp current showing on my ammeter.

So my question is, does anyone have a not-in-use Synchronome that can be checked to see what the resistance is on that?

And my other, key question: if it turns out that others do have the 11 ohms as Mitchell mentions, what can have happened to mine to make it be different? Looking at the wiring, one wire goes into the bottom coil and another wire comes out the top coil so they do both seem to be wired up.

Thanks
Brian


Brian Cracknell
 

I think you are right - I need a couple of days off work and peace and quiet to sort it out. Lockdown means the house is still full of children that I would love to get back to school out the way. I've taken all the non-electric parts off in the past to clean all the pivots and things but never the fine wiring on & behind the coils. As you say, none of it is beyond the wit of man.
Brian



From: synchronome1@groups.io <synchronome1@groups.io> on behalf of H Hal via groups.io <haal@...>
Sent: 29 June 2020 15:11
To: synchronome1@groups.io <synchronome1@groups.io>
Subject: Re: [synchronomeelectricclock] Total Resistance In The Synchronome?
 
Brian,
 
In my experience you will find the problem, if indeed there is one by pulling the the thing apart.
 
Plenty of room to leave parts overnight
 
Lots of photos and drawings as you go
 
all screws, bolts, washers in the order you remove them and labelled if necessary in an ice cube holder or some such
 
as you take it apart, the coil connections/terminals willreveal themselves, measure resistance of individual coils to hunt down the problem
 
 
what you really need is an excuse to spend a fewdays on it without having to go to work.....hang on!
 
 
 
good luck
 
hal  uk
 
ps
 
I have never set up my clocks/systems measuring voltage.
If all electrical connections, coils, switches are “good” then I wire up and include an ammeter to monitor the current...of course you need to know roughly the voltage that will be required but if you have a reasonable power supply you can start from 0V and increase as you go...when all is good you can source a final power supply of slightly higher voltage you got to and tweak the current by adding extra resistance
 
 
 
hal
 
uk
 
 
 
From: Brian Cracknell
Sent: Monday, June 29, 2020 2:55 PM
To: synchronome1@groups.io
Subject: Re: [synchronomeelectricclock] Total Resistance In The Synchronome?
 
Hal, Ian, thanks for the replies. I did think the maths worked out a bit suspiciously as if only one coil was connected but how do I go about proving the function of either coil? The tails of those coils look very delicate so I am a bit hesitant to start poking around too much unless I have to. I would like to follow the wiring though but I am not sure what the flow of wires should be. The coils "input" wire from the bottom of the armature disappears under the lower coil and presumably connects into that wire-wound resistor that Ian mentioned which I can just see between the coils right at the back and then the flow must come back into the first coil again, thence to the second one - they are in series I take it? I can't seem to find a circuit diagram anywhere.
 
Both coils have two wires connected as far as I can make out in the tight space. If the bottom coil was broken I had assumed no current could flow through the whole circuit? (Unless it had been bypassed but I can not see that this is the case.)
 
By the way, the other movements I have looked at on the computer have the wire from the armature going into a hole through the movement plate below the lower coil, just above the armature return spring. My clock doesn't have that hole so presumably that was a change in design later on.
 
The clock works reasonably well but has never (in the 10 years I have owned it) kept time precisely. So I keep fiddling with it and this is just the latest anomaly I have noticed.
 
Brian
 

From: synchronome1@groups.io <synchronome1@groups.io> on behalf of H Hal via groups.io <haal@...>
Sent: 29 June 2020 13:23
To: synchronome1@groups.io <synchronome1@groups.io>
Subject: Re: [synchronomeelectricclock] Total Resistance In The Synchronome?
 
I will check mine when I get into the workshop.
 
In the mean time what jumps out for me is that your 7 ohms I presume is total resistance so your main solenoid has 7 minus 2.45= 4.55 ohms
 
now if one of the two main coils has failed (shorted) the main resistance would be half of 8.7 ie 4.35 with a little resistance from the shorted coil giving 4.55 ohms
 
 
in other words I would suspect one of the main coils to be wired incorrectly or shorted out
 
 
 
hal
 
uk
 
From: Brian Cracknell
Sent: Monday, June 29, 2020 11:31 AM
To: synchronome1@groups.io
Subject: [synchronomeelectricclock] Total Resistance In The Synchronome?
 
According to Mitchell's "Setting to Work" instructions the total resistance in the Synchronome is made up of of 8.7 ohms (main solenoid) and 2.45 ohms (pilot slave) giving around 11.15 ohms total. My Synchronome however (an early 1920s, apparently unfiddled-with one with the original green cotton still on the coils) seems to have a resistance of 7.00 ohms showing on the ohmmeter when the circuit is closed. This reading is also supported by the fact that my power supply shows 3.3 volts on the voltmeter and when I add a 3 ohm resistor (providing 10 ohms total resistance) I get the required 0.33 amp current showing on my ammeter.

So my question is, does anyone have a not-in-use Synchronome that can be checked to see what the resistance is on that?

And my other, key question: if it turns out that others do have the 11 ohms as Mitchell mentions, what can have happened to mine to make it be different? Looking at the wiring, one wire goes into the bottom coil and another wire comes out the top coil so they do both seem to be wired up.

Thanks
Brian


Brian Cracknell
 

Thanks John.

Hmm, doing this only shows open circuit (trying various places on the chassis to the terminal) whereas measuring between the terminal and the armature contact itself gives 4.5 ohms which I suppose makes sense given the 7 ohms overall including pilot dial. I will have to take the coils off and have a better look at the wiring in due course to check what is going on.

Regarding timekeeping, the clock can run for a couple of weeks or so with pleasing predictability and then for no obvious reason (ie no great change in pressure or temperature) it will suddenly switch to a gain or a loss of up to a second per day or greater and stay like that for weeks. I never adjust the thread on the bob and only ever add/remove small weights. 

One day it will run perfectly.

Brian


From: synchronome1@groups.io <synchronome1@groups.io> on behalf of John Hubert <jfphubert@...>
Sent: 29 June 2020 15:04
To: synchronome1@groups.io <synchronome1@groups.io>
Subject: Re: [synchronomeelectricclock] Total Resistance In The Synchronome?
 
The coils are indeed connected in series - and the (one) resistor is in parallel with the two series coils.  Its value is roughly 10x that of the coils.

The coils are connected to the chassis at one end (the one that goes to the contact on the armature) and to the (lower on most clocks, but centre on clocks with three terminals) terminal screw, so measuring between that terminal and chassis should give the resistance of the combination of the two coils in series with the parallel resistor.  IF there is a short to chassis at the point where the coils join - then you would only measure the resistance of one coil.

The electrical side would not of course vary the timekeeping, which should be typically a very few seconds a week or better.


John Hubert





On 29 Jun 2020, at 14:55, Brian Cracknell <brcracknell@...> wrote:

Hal, Ian, thanks for the replies. I did think the maths worked out a bit suspiciously as if only one coil was connected but how do I go about proving the function of either coil? The tails of those coils look very delicate so I am a bit hesitant to start poking around too much unless I have to. I would like to follow the wiring though but I am not sure what the flow of wires should be. The coils "input" wire from the bottom of the armature disappears under the lower coil and presumably connects into that wire-wound resistor that Ian mentioned which I can just see between the coils right at the back and then the flow must come back into the first coil again, thence to the second one - they are in series I take it? I can't seem to find a circuit diagram anywhere.

Both coils have two wires connected as far as I can make out in the tight space. If the bottom coil was broken I had assumed no current could flow through the whole circuit? (Unless it had been bypassed but I can not see that this is the case.)

By the way, the other movements I have looked at on the computer have the wire from the armature going into a hole through the movement plate below the lower coil, just above the armature return spring. My clock doesn't have that hole so presumably that was a change in design later on.

The clock works reasonably well but has never (in the 10 years I have owned it) kept time precisely. So I keep fiddling with it and this is just the latest anomaly I have noticed.

Brian


From: synchronome1@groups.io <synchronome1@groups.io> on behalf of H Hal via groups.io <haal@...>
Sent: 29 June 2020 13:23
To: synchronome1@groups.io <synchronome1@groups.io>
Subject: Re: [synchronomeelectricclock] Total Resistance In The Synchronome?
 
I will check mine when I get into the workshop.
 
In the mean time what jumps out for me is that your 7 ohms I presume is total resistance so your main solenoid has 7 minus 2.45= 4.55 ohms
 
now if one of the two main coils has failed (shorted) the main resistance would be half of 8.7 ie 4.35 with a little resistance from the shorted coil giving 4.55 ohms
 
 
in other words I would suspect one of the main coils to be wired incorrectly or shorted out
 
 
 
hal
 
uk
 
From: Brian Cracknell
Sent: Monday, June 29, 2020 11:31 AM
Subject: [synchronomeelectricclock] Total Resistance In The Synchronome?
 
According to Mitchell's "Setting to Work" instructions the total resistance in the Synchronome is made up of of 8.7 ohms (main solenoid) and 2.45 ohms (pilot slave) giving around 11.15 ohms total. My Synchronome however (an early 1920s, apparently unfiddled-with one with the original green cotton still on the coils) seems to have a resistance of 7.00 ohms showing on the ohmmeter when the circuit is closed. This reading is also supported by the fact that my power supply shows 3.3 volts on the voltmeter and when I add a 3 ohm resistor (providing 10 ohms total resistance) I get the required 0.33 amp current showing on my ammeter.

So my question is, does anyone have a not-in-use Synchronome that can be checked to see what the resistance is on that?

And my other, key question: if it turns out that others do have the 11 ohms as Mitchell mentions, what can have happened to mine to make it be different? Looking at the wiring, one wire goes into the bottom coil and another wire comes out the top coil so they do both seem to be wired up.

Thanks
Brian 


Odell, Edward
 

Hi all,

I am not sure there is much wrong, the expected resistance of the master and slave coils in series with a parallel resistance of about 110 ohm is only around 10 ohms anyway.  OK, so coils are not simple resistors, but close enough.  I haven’t measured this way before, but removing battery and just measuring the entire circuit through the master with pilot dial, including through the contacts, gives 8 ohms on my 1930 clock, and that resets fine.  Not much different from yours.  Coils can short inside, but leaving them alone might be the best to not induce further problems unless you know something is wrong.  As others said, timekeeping won’t be affected.  Bob Miles ‘synchronome bible’ gives 9 Ohms approx. for master and 2.5 for slave.  He doesn’t give a value for the spark quench resistor but 10x the coil is usual (I was never sure whether its 10x the master coils only or master+ slave).  Its fragile to remove unless really necessary.  If it resets snappily after cleaning contacts at 4.5 volts (or if the 330mA is achieved at around that voltage) I would leave it alone and clean the mechanical elements.

Eddy Odell

 

From: synchronome1@groups.io <synchronome1@groups.io> On Behalf Of Brian Cracknell via groups.io
Sent: 29 June 2020 15:43
To: synchronome1@groups.io
Subject: Re: [synchronomeelectricclock] Total Resistance In The Synchronome?

 

Thanks John.

 

Hmm, doing this only shows open circuit (trying various places on the chassis to the terminal) whereas measuring between the terminal and the armature contact itself gives 4.5 ohms which I suppose makes sense given the 7 ohms overall including pilot dial. I will have to take the coils off and have a better look at the wiring in due course to check what is going on.

 

Regarding timekeeping, the clock can run for a couple of weeks or so with pleasing predictability and then for no obvious reason (ie no great change in pressure or temperature) it will suddenly switch to a gain or a loss of up to a second per day or greater and stay like that for weeks. I never adjust the thread on the bob and only ever add/remove small weights. 

 

One day it will run perfectly.

 

Brian

 


From: synchronome1@groups.io <synchronome1@groups.io> on behalf of John Hubert <jfphubert@...>
Sent: 29 June 2020 15:04
To:
synchronome1@groups.io <synchronome1@groups.io>
Subject: Re: [synchronomeelectricclock] Total Resistance In The Synchronome?

 

The coils are indeed connected in series - and the (one) resistor is in parallel with the two series coils.  Its value is roughly 10x that of the coils.

 

The coils are connected to the chassis at one end (the one that goes to the contact on the armature) and to the (lower on most clocks, but centre on clocks with three terminals) terminal screw, so measuring between that terminal and chassis should give the resistance of the combination of the two coils in series with the parallel resistor.  IF there is a short to chassis at the point where the coils join - then you would only measure the resistance of one coil.

 

The electrical side would not of course vary the timekeeping, which should be typically a very few seconds a week or better.

 

 

John Hubert







On 29 Jun 2020, at 14:55, Brian Cracknell <brcracknell@...> wrote:

 

Hal, Ian, thanks for the replies. I did think the maths worked out a bit suspiciously as if only one coil was connected but how do I go about proving the function of either coil? The tails of those coils look very delicate so I am a bit hesitant to start poking around too much unless I have to. I would like to follow the wiring though but I am not sure what the flow of wires should be. The coils "input" wire from the bottom of the armature disappears under the lower coil and presumably connects into that wire-wound resistor that Ian mentioned which I can just see between the coils right at the back and then the flow must come back into the first coil again, thence to the second one - they are in series I take it? I can't seem to find a circuit diagram anywhere.

 

Both coils have two wires connected as far as I can make out in the tight space. If the bottom coil was broken I had assumed no current could flow through the whole circuit? (Unless it had been bypassed but I can not see that this is the case.)

 

By the way, the other movements I have looked at on the computer have the wire from the armature going into a hole through the movement plate below the lower coil, just above the armature return spring. My clock doesn't have that hole so presumably that was a change in design later on.

 

The clock works reasonably well but has never (in the 10 years I have owned it) kept time precisely. So I keep fiddling with it and this is just the latest anomaly I have noticed.

 

Brian

 


From: synchronome1@groups.io <synchronome1@groups.io> on behalf of H Hal via groups.io <haal@...>
Sent: 29 June 2020 13:23
To: synchronome1@groups.io <synchronome1@groups.io>
Subject: Re: [synchronomeelectricclock] Total Resistance In The Synchronome?

 

I will check mine when I get into the workshop.

 

In the mean time what jumps out for me is that your 7 ohms I presume is total resistance so your main solenoid has 7 minus 2.45= 4.55 ohms

 

now if one of the two main coils has failed (shorted) the main resistance would be half of 8.7 ie 4.35 with a little resistance from the shorted coil giving 4.55 ohms

 

 

in other words I would suspect one of the main coils to be wired incorrectly or shorted out

 

 

 

hal

 

uk

 

From: Brian Cracknell

Sent: Monday, June 29, 2020 11:31 AM

Subject: [synchronomeelectricclock] Total Resistance In The Synchronome?

 

According to Mitchell's "Setting to Work" instructions the total resistance in the Synchronome is made up of of 8.7 ohms (main solenoid) and 2.45 ohms (pilot slave) giving around 11.15 ohms total. My Synchronome however (an early 1920s, apparently unfiddled-with one with the original green cotton still on the coils) seems to have a resistance of 7.00 ohms showing on the ohmmeter when the circuit is closed. This reading is also supported by the fact that my power supply shows 3.3 volts on the voltmeter and when I add a 3 ohm resistor (providing 10 ohms total resistance) I get the required 0.33 amp current showing on my ammeter.

So my question is, does anyone have a not-in-use Synchronome that can be checked to see what the resistance is on that?

And my other, key question: if it turns out that others do have the 11 ohms as Mitchell mentions, what can have happened to mine to make it be different? Looking at the wiring, one wire goes into the bottom coil and another wire comes out the top coil so they do both seem to be wired up.

Thanks
Brian 

 


John Hubert
 

To clarify, the top terminal connects to the gravity arm side of the switch.  Usually the connection  is a loop of wire.

The armature side of the switch connects to the chassis (some clocks have a small jump lead, others rely on the armature hinge).  This is the junction between the coils and the switch, both of which connect to the chassis.

The coils connect to the chassis at one end - and the lower terminal (two terminal clocks) at the other end.  The resistor is across the two series connected coils.  The junction point between the two coils is not connected to anything else.

Where a third terminal is fitted, it is connected to the chassis.  This was used when the clock was used with a Synchronome Distribution Board.

John

On 29 Jun 2020, at 15:43, Brian Cracknell <brcracknell@...> wrote:

Thanks John.

Hmm, doing this only shows open circuit (trying various places on the chassis to the terminal) whereas measuring between the terminal and the armature contact itself gives 4.5 ohms which I suppose makes sense given the 7 ohms overall including pilot dial. I will have to take the coils off and have a better look at the wiring in due course to check what is going on.

Regarding timekeeping, the clock can run for a couple of weeks or so with pleasing predictability and then for no obvious reason (ie no great change in pressure or temperature) it will suddenly switch to a gain or a loss of up to a second per day or greater and stay like that for weeks. I never adjust the thread on the bob and only ever add/remove small weights. 

One day it will run perfectly.

Brian


From: synchronome1@groups.io <synchronome1@groups.io> on behalf of John Hubert <jfphubert@...>
Sent: 29 June 2020 15:04
To: synchronome1@groups.io <synchronome1@groups.io>
Subject: Re: [synchronomeelectricclock] Total Resistance In The Synchronome?
 
The coils are indeed connected in series - and the (one) resistor is in parallel with the two series coils.  Its value is roughly 10x that of the coils.

The coils are connected to the chassis at one end (the one that goes to the contact on the armature) and to the (lower on most clocks, but centre on clocks with three terminals) terminal screw, so measuring between that terminal and chassis should give the resistance of the combination of the two coils in series with the parallel resistor.  IF there is a short to chassis at the point where the coils join - then you would only measure the resistance of one coil.

The electrical side would not of course vary the timekeeping, which should be typically a very few seconds a week or better.


John Hubert





On 29 Jun 2020, at 14:55, Brian Cracknell <brcracknell@...> wrote:

Hal, Ian, thanks for the replies. I did think the maths worked out a bit suspiciously as if only one coil was connected but how do I go about proving the function of either coil? The tails of those coils look very delicate so I am a bit hesitant to start poking around too much unless I have to. I would like to follow the wiring though but I am not sure what the flow of wires should be. The coils "input" wire from the bottom of the armature disappears under the lower coil and presumably connects into that wire-wound resistor that Ian mentioned which I can just see between the coils right at the back and then the flow must come back into the first coil again, thence to the second one - they are in series I take it? I can't seem to find a circuit diagram anywhere.

Both coils have two wires connected as far as I can make out in the tight space. If the bottom coil was broken I had assumed no current could flow through the whole circuit? (Unless it had been bypassed but I can not see that this is the case.)

By the way, the other movements I have looked at on the computer have the wire from the armature going into a hole through the movement plate below the lower coil, just above the armature return spring. My clock doesn't have that hole so presumably that was a change in design later on.

The clock works reasonably well but has never (in the 10 years I have owned it) kept time precisely. So I keep fiddling with it and this is just the latest anomaly I have noticed.

Brian


From: synchronome1@groups.io <synchronome1@groups.io> on behalf of H Hal via groups.io <haal@...>
Sent: 29 June 2020 13:23
To: synchronome1@groups.io <synchronome1@groups.io>
Subject: Re: [synchronomeelectricclock] Total Resistance In The Synchronome?
 
I will check mine when I get into the workshop.
 
In the mean time what jumps out for me is that your 7 ohms I presume is total resistance so your main solenoid has 7 minus 2.45= 4.55 ohms
 
now if one of the two main coils has failed (shorted) the main resistance would be half of 8.7 ie 4.35 with a little resistance from the shorted coil giving 4.55 ohms
 
 
in other words I would suspect one of the main coils to be wired incorrectly or shorted out
 
 
 
hal
 
uk
 
From: Brian Cracknell
Sent: Monday, June 29, 2020 11:31 AM
Subject: [synchronomeelectricclock] Total Resistance In The Synchronome?
 
According to Mitchell's "Setting to Work" instructions the total resistance in the Synchronome is made up of of 8.7 ohms (main solenoid) and 2.45 ohms (pilot slave) giving around 11.15 ohms total. My Synchronome however (an early 1920s, apparently unfiddled-with one with the original green cotton still on the coils) seems to have a resistance of 7.00 ohms showing on the ohmmeter when the circuit is closed. This reading is also supported by the fact that my power supply shows 3.3 volts on the voltmeter and when I add a 3 ohm resistor (providing 10 ohms total resistance) I get the required 0.33 amp current showing on my ammeter.

So my question is, does anyone have a not-in-use Synchronome that can be checked to see what the resistance is on that?

And my other, key question: if it turns out that others do have the 11 ohms as Mitchell mentions, what can have happened to mine to make it be different? Looking at the wiring, one wire goes into the bottom coil and another wire comes out the top coil so they do both seem to be wired up.

Thanks
Brian 



Peter Torry
 

Just out of interest I have measured a 1930s example that I have in the workshop and the main coils and quench resistor combined measure 7.6 R and the pilot dial 3.2 R.  I would expect there to be a spread of resistance over a production run and also a variation between different suppliers therefore may I suggest that all is normal.  Just set the current for the system and let it run.

Regards

Peter   UK


On 29/06/2020 13:23, H Hal via groups.io wrote:
I will check mine when I get into the workshop.
 
In the mean time what jumps out for me is that your 7 ohms I presume is total resistance so your main solenoid has 7 minus 2.45= 4.55 ohms
 
now if one of the two main coils has failed (shorted) the main resistance would be half of 8.7 ie 4.35 with a little resistance from the shorted coil giving 4.55 ohms
 
 
in other words I would suspect one of the main coils to be wired incorrectly or shorted out
 
 
 
hal
 
uk
 
From: Brian Cracknell
Sent: Monday, June 29, 2020 11:31 AM
To: synchronome1@groups.io
Subject: [synchronomeelectricclock] Total Resistance In The Synchronome?
 
According to Mitchell's "Setting to Work" instructions the total resistance in the Synchronome is made up of of 8.7 ohms (main solenoid) and 2.45 ohms (pilot slave) giving around 11.15 ohms total. My Synchronome however (an early 1920s, apparently unfiddled-with one with the original green cotton still on the coils) seems to have a resistance of 7.00 ohms showing on the ohmmeter when the circuit is closed. This reading is also supported by the fact that my power supply shows 3.3 volts on the voltmeter and when I add a 3 ohm resistor (providing 10 ohms total resistance) I get the required 0.33 amp current showing on my ammeter.

So my question is, does anyone have a not-in-use Synchronome that can be checked to see what the resistance is on that?

And my other, key question: if it turns out that others do have the 11 ohms as Mitchell mentions, what can have happened to mine to make it be different? Looking at the wiring, one wire goes into the bottom coil and another wire comes out the top coil so they do both seem to be wired up.

Thanks
Brian


Andrew Nahum
 

If the clock ran continuously and it re-set the gravity arm reliably why do you suspect the coils?  Timekeeping errors must surely lie elsewhere with pendulum, suspension or even wall mounting. To my mind the greatest risk to old shellacked coils is touching and moving anything at all, including the wire where it comes in and out. Admittedly the shellac insulation is probably pretty crumbly -  which is a good reason not to disturb it at all.  I’m used to old motorcycle magnetos where the high tension windings do fail at thousands of volts. But the voltage in the Synchronome is trivial. I run mine (with just one slave the clock’s own dial) on 3 volts (2 ‘C’ Duracells) and they last  a year. 

But I’ll get around to measuring the ohms soon I hope. 

On 29 Jun 2020, at 15:22, Brian Cracknell <brcracknell@...> wrote:


I think you are right - I need a couple of days off work and peace and quiet to sort it out. Lockdown means the house is still full of children that I would love to get back to school out the way. I've taken all the non-electric parts off in the past to clean all the pivots and things but never the fine wiring on & behind the coils. As you say, none of it is beyond the wit of man.
Brian



From: synchronome1@groups.io <synchronome1@groups.io> on behalf of H Hal via groups.io <haal@...>
Sent: 29 June 2020 15:11
To: synchronome1@groups.io <synchronome1@groups.io>
Subject: Re: [synchronomeelectricclock] Total Resistance In The Synchronome?
 
Brian,
 
In my experience you will find the problem, if indeed there is one by pulling the the thing apart.
 
Plenty of room to leave parts overnight
 
Lots of photos and drawings as you go
 
all screws, bolts, washers in the order you remove them and labelled if necessary in an ice cube holder or some such
 
as you take it apart, the coil connections/terminals willreveal themselves, measure resistance of individual coils to hunt down the problem
 
 
what you really need is an excuse to spend a fewdays on it without having to go to work.....hang on!
 
 
 
good luck
 
hal  uk
 
ps
 
I have never set up my clocks/systems measuring voltage.
If all electrical connections, coils, switches are “good” then I wire up and include an ammeter to monitor the current...of course you need to know roughly the voltage that will be required but if you have a reasonable power supply you can start from 0V and increase as you go...when all is good you can source a final power supply of slightly higher voltage you got to and tweak the current by adding extra resistance
 
 
 
hal
 
uk
 
 
 
From: Brian Cracknell
Sent: Monday, June 29, 2020 2:55 PM
To: synchronome1@groups.io
Subject: Re: [synchronomeelectricclock] Total Resistance In The Synchronome?
 
Hal, Ian, thanks for the replies. I did think the maths worked out a bit suspiciously as if only one coil was connected but how do I go about proving the function of either coil? The tails of those coils look very delicate so I am a bit hesitant to start poking around too much unless I have to. I would like to follow the wiring though but I am not sure what the flow of wires should be. The coils "input" wire from the bottom of the armature disappears under the lower coil and presumably connects into that wire-wound resistor that Ian mentioned which I can just see between the coils right at the back and then the flow must come back into the first coil again, thence to the second one - they are in series I take it? I can't seem to find a circuit diagram anywhere.
 
Both coils have two wires connected as far as I can make out in the tight space. If the bottom coil was broken I had assumed no current could flow through the whole circuit? (Unless it had been bypassed but I can not see that this is the case.)
 
By the way, the other movements I have looked at on the computer have the wire from the armature going into a hole through the movement plate below the lower coil, just above the armature return spring. My clock doesn't have that hole so presumably that was a change in design later on.
 
The clock works reasonably well but has never (in the 10 years I have owned it) kept time precisely. So I keep fiddling with it and this is just the latest anomaly I have noticed.
 
Brian
 

From: synchronome1@groups.io <synchronome1@groups.io> on behalf of H Hal via groups.io <haal@...>
Sent: 29 June 2020 13:23
To: synchronome1@groups.io <synchronome1@groups.io>
Subject: Re: [synchronomeelectricclock] Total Resistance In The Synchronome?
 
I will check mine when I get into the workshop.
 
In the mean time what jumps out for me is that your 7 ohms I presume is total resistance so your main solenoid has 7 minus 2.45= 4.55 ohms
 
now if one of the two main coils has failed (shorted) the main resistance would be half of 8.7 ie 4.35 with a little resistance from the shorted coil giving 4.55 ohms
 
 
in other words I would suspect one of the main coils to be wired incorrectly or shorted out
 
 
 
hal
 
uk
 
From: Brian Cracknell
Sent: Monday, June 29, 2020 11:31 AM
To: synchronome1@groups.io
Subject: [synchronomeelectricclock] Total Resistance In The Synchronome?
 
According to Mitchell's "Setting to Work" instructions the total resistance in the Synchronome is made up of of 8.7 ohms (main solenoid) and 2.45 ohms (pilot slave) giving around 11.15 ohms total. My Synchronome however (an early 1920s, apparently unfiddled-with one with the original green cotton still on the coils) seems to have a resistance of 7.00 ohms showing on the ohmmeter when the circuit is closed. This reading is also supported by the fact that my power supply shows 3.3 volts on the voltmeter and when I add a 3 ohm resistor (providing 10 ohms total resistance) I get the required 0.33 amp current showing on my ammeter.

So my question is, does anyone have a not-in-use Synchronome that can be checked to see what the resistance is on that?

And my other, key question: if it turns out that others do have the 11 ohms as Mitchell mentions, what can have happened to mine to make it be different? Looking at the wiring, one wire goes into the bottom coil and another wire comes out the top coil so they do both seem to be wired up.

Thanks
Brian


Brian Cracknell
 

Andrew, I suppose I just want the clock to behave in a standard way like others. Mine too runs on 3v nominal (actually showing as 3.3v) but I had to add the 3 ohms to get the current right and all the others I have heard of never had this issue.
It does reset the gravity arm but the clock is in the lounge and I sit listening to it on an evening and the force of the impulse used to sound slightly variable - sometimes it sounded crisp and sometimes it sounded sluggish so I thought I would investigate further. I had loose wiring issues in the old power supply and this probably caused the random sluggish impulses which in turn affected the timekeeping because the roller stayed on the pallet longer before being reset sometimes but that issue hopefully got fixed with a new power supply which is when I discovered the lower resistance in the clock when I was getting the current right in the new set up.
Maybe it isn't a problem and over time the new power supply with reliable wiring will show a consistent pulse duration and the timekeeping deviations will cease. But it's always nice to know what is going on inside the thing.
Brian


From: synchronome1@groups.io <synchronome1@groups.io> on behalf of Andrew Nahum <andrew.nahum@...>
Sent: 29 June 2020 23:09
To: synchronome1@groups.io <synchronome1@groups.io>
Subject: Re: [synchronomeelectricclock] Total Resistance In The Synchronome?
 
If the clock ran continuously and it re-set the gravity arm reliably why do you suspect the coils?  Timekeeping errors must surely lie elsewhere with pendulum, suspension or even wall mounting. To my mind the greatest risk to old shellacked coils is touching and moving anything at all, including the wire where it comes in and out. Admittedly the shellac insulation is probably pretty crumbly -  which is a good reason not to disturb it at all.  I’m used to old motorcycle magnetos where the high tension windings do fail at thousands of volts. But the voltage in the Synchronome is trivial. I run mine (with just one slave the clock’s own dial) on 3 volts (2 ‘C’ Duracells) and they last  a year. 

But I’ll get around to measuring the ohms soon I hope. 

On 29 Jun 2020, at 15:22, Brian Cracknell <brcracknell@...> wrote:


I think you are right - I need a couple of days off work and peace and quiet to sort it out. Lockdown means the house is still full of children that I would love to get back to school out the way. I've taken all the non-electric parts off in the past to clean all the pivots and things but never the fine wiring on & behind the coils. As you say, none of it is beyond the wit of man.
Brian



From: synchronome1@groups.io <synchronome1@groups.io> on behalf of H Hal via groups.io <haal@...>
Sent: 29 June 2020 15:11
To: synchronome1@groups.io <synchronome1@groups.io>
Subject: Re: [synchronomeelectricclock] Total Resistance In The Synchronome?
 
Brian,
 
In my experience you will find the problem, if indeed there is one by pulling the the thing apart.
 
Plenty of room to leave parts overnight
 
Lots of photos and drawings as you go
 
all screws, bolts, washers in the order you remove them and labelled if necessary in an ice cube holder or some such
 
as you take it apart, the coil connections/terminals willreveal themselves, measure resistance of individual coils to hunt down the problem
 
 
what you really need is an excuse to spend a fewdays on it without having to go to work.....hang on!
 
 
 
good luck
 
hal  uk
 
ps
 
I have never set up my clocks/systems measuring voltage.
If all electrical connections, coils, switches are “good” then I wire up and include an ammeter to monitor the current...of course you need to know roughly the voltage that will be required but if you have a reasonable power supply you can start from 0V and increase as you go...when all is good you can source a final power supply of slightly higher voltage you got to and tweak the current by adding extra resistance
 
 
 
hal
 
uk
 
 
 
From: Brian Cracknell
Sent: Monday, June 29, 2020 2:55 PM
To: synchronome1@groups.io
Subject: Re: [synchronomeelectricclock] Total Resistance In The Synchronome?
 
Hal, Ian, thanks for the replies. I did think the maths worked out a bit suspiciously as if only one coil was connected but how do I go about proving the function of either coil? The tails of those coils look very delicate so I am a bit hesitant to start poking around too much unless I have to. I would like to follow the wiring though but I am not sure what the flow of wires should be. The coils "input" wire from the bottom of the armature disappears under the lower coil and presumably connects into that wire-wound resistor that Ian mentioned which I can just see between the coils right at the back and then the flow must come back into the first coil again, thence to the second one - they are in series I take it? I can't seem to find a circuit diagram anywhere.
 
Both coils have two wires connected as far as I can make out in the tight space. If the bottom coil was broken I had assumed no current could flow through the whole circuit? (Unless it had been bypassed but I can not see that this is the case.)
 
By the way, the other movements I have looked at on the computer have the wire from the armature going into a hole through the movement plate below the lower coil, just above the armature return spring. My clock doesn't have that hole so presumably that was a change in design later on.
 
The clock works reasonably well but has never (in the 10 years I have owned it) kept time precisely. So I keep fiddling with it and this is just the latest anomaly I have noticed.
 
Brian
 

From: synchronome1@groups.io <synchronome1@groups.io> on behalf of H Hal via groups.io <haal@...>
Sent: 29 June 2020 13:23
To: synchronome1@groups.io <synchronome1@groups.io>
Subject: Re: [synchronomeelectricclock] Total Resistance In The Synchronome?
 
I will check mine when I get into the workshop.
 
In the mean time what jumps out for me is that your 7 ohms I presume is total resistance so your main solenoid has 7 minus 2.45= 4.55 ohms
 
now if one of the two main coils has failed (shorted) the main resistance would be half of 8.7 ie 4.35 with a little resistance from the shorted coil giving 4.55 ohms
 
 
in other words I would suspect one of the main coils to be wired incorrectly or shorted out
 
 
 
hal
 
uk
 
From: Brian Cracknell
Sent: Monday, June 29, 2020 11:31 AM
To: synchronome1@groups.io
Subject: [synchronomeelectricclock] Total Resistance In The Synchronome?
 
According to Mitchell's "Setting to Work" instructions the total resistance in the Synchronome is made up of of 8.7 ohms (main solenoid) and 2.45 ohms (pilot slave) giving around 11.15 ohms total. My Synchronome however (an early 1920s, apparently unfiddled-with one with the original green cotton still on the coils) seems to have a resistance of 7.00 ohms showing on the ohmmeter when the circuit is closed. This reading is also supported by the fact that my power supply shows 3.3 volts on the voltmeter and when I add a 3 ohm resistor (providing 10 ohms total resistance) I get the required 0.33 amp current showing on my ammeter.

So my question is, does anyone have a not-in-use Synchronome that can be checked to see what the resistance is on that?

And my other, key question: if it turns out that others do have the 11 ohms as Mitchell mentions, what can have happened to mine to make it be different? Looking at the wiring, one wire goes into the bottom coil and another wire comes out the top coil so they do both seem to be wired up.

Thanks
Brian


Brian Cracknell
 

John, I can't see any visible evidence of my clock using the chassis at all for the circuit. The jump lead from the armature does not visibly connect to the chassis - whereas the others I have looked at do connect to the chassis at a small visible terminal just above the armature spring. Instead, the jump lead disappears behind the coils to a hidden location - either to a chassis terminal there possibly or directly to something else. There is no sign of a terminal hole in the chassis at the normal location either. It is all very strange. The chassis doesn't seem like a very good conductor anyway - I checked for continuity at various points on it with the ohmmeter but it didn't manage to establish a circuit through the paint.
Brian


From: synchronome1@groups.io <synchronome1@groups.io> on behalf of John Hubert <jfphubert@...>
Sent: 29 June 2020 16:23
To: synchronome1@groups.io <synchronome1@groups.io>
Subject: Re: [synchronomeelectricclock] Total Resistance In The Synchronome?
 
To clarify, the top terminal connects to the gravity arm side of the switch.  Usually the connection  is a loop of wire.

The armature side of the switch connects to the chassis (some clocks have a small jump lead, others rely on the armature hinge).  This is the junction between the coils and the switch, both of which connect to the chassis.

The coils connect to the chassis at one end - and the lower terminal (two terminal clocks) at the other end.  The resistor is across the two series connected coils.  The junction point between the two coils is not connected to anything else.

Where a third terminal is fitted, it is connected to the chassis.  This was used when the clock was used with a Synchronome Distribution Board.

John

On 29 Jun 2020, at 15:43, Brian Cracknell <brcracknell@...> wrote:

Thanks John.

Hmm, doing this only shows open circuit (trying various places on the chassis to the terminal) whereas measuring between the terminal and the armature contact itself gives 4.5 ohms which I suppose makes sense given the 7 ohms overall including pilot dial. I will have to take the coils off and have a better look at the wiring in due course to check what is going on.

Regarding timekeeping, the clock can run for a couple of weeks or so with pleasing predictability and then for no obvious reason (ie no great change in pressure or temperature) it will suddenly switch to a gain or a loss of up to a second per day or greater and stay like that for weeks. I never adjust the thread on the bob and only ever add/remove small weights. 

One day it will run perfectly.

Brian


From: synchronome1@groups.io <synchronome1@groups.io> on behalf of John Hubert <jfphubert@...>
Sent: 29 June 2020 15:04
To: synchronome1@groups.io <synchronome1@groups.io>
Subject: Re: [synchronomeelectricclock] Total Resistance In The Synchronome?
 
The coils are indeed connected in series - and the (one) resistor is in parallel with the two series coils.  Its value is roughly 10x that of the coils.

The coils are connected to the chassis at one end (the one that goes to the contact on the armature) and to the (lower on most clocks, but centre on clocks with three terminals) terminal screw, so measuring between that terminal and chassis should give the resistance of the combination of the two coils in series with the parallel resistor.  IF there is a short to chassis at the point where the coils join - then you would only measure the resistance of one coil.

The electrical side would not of course vary the timekeeping, which should be typically a very few seconds a week or better.


John Hubert





On 29 Jun 2020, at 14:55, Brian Cracknell <brcracknell@...> wrote:

Hal, Ian, thanks for the replies. I did think the maths worked out a bit suspiciously as if only one coil was connected but how do I go about proving the function of either coil? The tails of those coils look very delicate so I am a bit hesitant to start poking around too much unless I have to. I would like to follow the wiring though but I am not sure what the flow of wires should be. The coils "input" wire from the bottom of the armature disappears under the lower coil and presumably connects into that wire-wound resistor that Ian mentioned which I can just see between the coils right at the back and then the flow must come back into the first coil again, thence to the second one - they are in series I take it? I can't seem to find a circuit diagram anywhere.

Both coils have two wires connected as far as I can make out in the tight space. If the bottom coil was broken I had assumed no current could flow through the whole circuit? (Unless it had been bypassed but I can not see that this is the case.)

By the way, the other movements I have looked at on the computer have the wire from the armature going into a hole through the movement plate below the lower coil, just above the armature return spring. My clock doesn't have that hole so presumably that was a change in design later on.

The clock works reasonably well but has never (in the 10 years I have owned it) kept time precisely. So I keep fiddling with it and this is just the latest anomaly I have noticed.

Brian


From: synchronome1@groups.io <synchronome1@groups.io> on behalf of H Hal via groups.io <haal@...>
Sent: 29 June 2020 13:23
To: synchronome1@groups.io <synchronome1@groups.io>
Subject: Re: [synchronomeelectricclock] Total Resistance In The Synchronome?
 
I will check mine when I get into the workshop.
 
In the mean time what jumps out for me is that your 7 ohms I presume is total resistance so your main solenoid has 7 minus 2.45= 4.55 ohms
 
now if one of the two main coils has failed (shorted) the main resistance would be half of 8.7 ie 4.35 with a little resistance from the shorted coil giving 4.55 ohms
 
 
in other words I would suspect one of the main coils to be wired incorrectly or shorted out
 
 
 
hal
 
uk
 
From: Brian Cracknell
Sent: Monday, June 29, 2020 11:31 AM
Subject: [synchronomeelectricclock] Total Resistance In The Synchronome?
 
According to Mitchell's "Setting to Work" instructions the total resistance in the Synchronome is made up of of 8.7 ohms (main solenoid) and 2.45 ohms (pilot slave) giving around 11.15 ohms total. My Synchronome however (an early 1920s, apparently unfiddled-with one with the original green cotton still on the coils) seems to have a resistance of 7.00 ohms showing on the ohmmeter when the circuit is closed. This reading is also supported by the fact that my power supply shows 3.3 volts on the voltmeter and when I add a 3 ohm resistor (providing 10 ohms total resistance) I get the required 0.33 amp current showing on my ammeter.

So my question is, does anyone have a not-in-use Synchronome that can be checked to see what the resistance is on that?

And my other, key question: if it turns out that others do have the 11 ohms as Mitchell mentions, what can have happened to mine to make it be different? Looking at the wiring, one wire goes into the bottom coil and another wire comes out the top coil so they do both seem to be wired up.

Thanks
Brian 



John Hubert
 

I can’t explain why your clock appears to be different, but all clocks I have come across use the chassis - and in fact, the armature contact isn’t provided with any way of insulating it from the chassis.  I have never tried this - but I see no reason why you couldn’t run a small current (say 100 mA or less) through the system and use an iron item to check for magnetism at the two coils?  As I say, I’ve never tried it, but a low current shouldn’t cause any damage - and I would think would be detectable by ’the end of a screwdriver for instance.  Anyone tried this?

John

On 30 Jun 2020, at 09:11, Brian Cracknell <brcracknell@...> wrote:

John, I can't see any visible evidence of my clock using the chassis at all for the circuit. The jump lead from the armature does not visibly connect to the chassis - whereas the others I have looked at do connect to the chassis at a small visible terminal just above the armature spring. Instead, the jump lead disappears behind the coils to a hidden location - either to a chassis terminal there possibly or directly to something else. There is no sign of a terminal hole in the chassis at the normal location either. It is all very strange. The chassis doesn't seem like a very good conductor anyway - I checked for continuity at various points on it with the ohmmeter but it didn't manage to establish a circuit through the paint.
Brian


From: synchronome1@groups.io <synchronome1@groups.io> on behalf of John Hubert <jfphubert@...>
Sent: 29 June 2020 16:23
To: synchronome1@groups.io <synchronome1@groups.io>
Subject: Re: [synchronomeelectricclock] Total Resistance In The Synchronome?
 
To clarify, the top terminal connects to the gravity arm side of the switch.  Usually the connection  is a loop of wire.

The armature side of the switch connects to the chassis (some clocks have a small jump lead, others rely on the armature hinge).  This is the junction between the coils and the switch, both of which connect to the chassis.

The coils connect to the chassis at one end - and the lower terminal (two terminal clocks) at the other end.  The resistor is across the two series connected coils.  The junction point between the two coils is not connected to anything else.

Where a third terminal is fitted, it is connected to the chassis.  This was used when the clock was used with a Synchronome Distribution Board.

John

On 29 Jun 2020, at 15:43, Brian Cracknell <brcracknell@...> wrote:

Thanks John.

Hmm, doing this only shows open circuit (trying various places on the chassis to the terminal) whereas measuring between the terminal and the armature contact itself gives 4.5 ohms which I suppose makes sense given the 7 ohms overall including pilot dial. I will have to take the coils off and have a better look at the wiring in due course to check what is going on.

Regarding timekeeping, the clock can run for a couple of weeks or so with pleasing predictability and then for no obvious reason (ie no great change in pressure or temperature) it will suddenly switch to a gain or a loss of up to a second per day or greater and stay like that for weeks. I never adjust the thread on the bob and only ever add/remove small weights. 

One day it will run perfectly.

Brian


 
From: synchronome1@groups.io <synchronome1@groups.io> on behalf of John Hubert <jfphubert@...>
Sent: 29 June 2020 15:04
To: synchronome1@groups.io <synchronome1@groups.io>
Subject: Re: [synchronomeelectricclock] Total Resistance In The Synchronome?
 
The coils are indeed connected in series - and the (one) resistor is in parallel with the two series coils.  Its value is roughly 10x that of the coils.

The coils are connected to the chassis at one end (the one that goes to the contact on the armature) and to the (lower on most clocks, but centre on clocks with three terminals) terminal screw, so measuring between that terminal and chassis should give the resistance of the combination of the two coils in series with the parallel resistor.  IF there is a short to chassis at the point where the coils join - then you would only measure the resistance of one coil.

The electrical side would not of course vary the timekeeping, which should be typically a very few seconds a week or better.


John Hubert





On 29 Jun 2020, at 14:55, Brian Cracknell <brcracknell@...> wrote:

Hal, Ian, thanks for the replies. I did think the maths worked out a bit suspiciously as if only one coil was connected but how do I go about proving the function of either coil? The tails of those coils look very delicate so I am a bit hesitant to start poking around too much unless I have to. I would like to follow the wiring though but I am not sure what the flow of wires should be. The coils "input" wire from the bottom of the armature disappears under the lower coil and presumably connects into that wire-wound resistor that Ian mentioned which I can just see between the coils right at the back and then the flow must come back into the first coil again, thence to the second one - they are in series I take it? I can't seem to find a circuit diagram anywhere.

Both coils have two wires connected as far as I can make out in the tight space. If the bottom coil was broken I had assumed no current could flow through the whole circuit? (Unless it had been bypassed but I can not see that this is the case.)

By the way, the other movements I have looked at on the computer have the wire from the armature going into a hole through the movement plate below the lower coil, just above the armature return spring. My clock doesn't have that hole so presumably that was a change in design later on.

The clock works reasonably well but has never (in the 10 years I have owned it) kept time precisely. So I keep fiddling with it and this is just the latest anomaly I have noticed.

Brian


From: synchronome1@groups.io <synchronome1@groups.io> on behalf of H Hal via groups.io <haal@...>
Sent: 29 June 2020 13:23
To: synchronome1@groups.io <synchronome1@groups.io>
Subject: Re: [synchronomeelectricclock] Total Resistance In The Synchronome?
 
I will check mine when I get into the workshop.
 
In the mean time what jumps out for me is that your 7 ohms I presume is total resistance so your main solenoid has 7 minus 2.45= 4.55 ohms
 
now if one of the two main coils has failed (shorted) the main resistance would be half of 8.7 ie 4.35 with a little resistance from the shorted coil giving 4.55 ohms
 
 
in other words I would suspect one of the main coils to be wired incorrectly or shorted out
 
 
 
hal
 
uk
 
From: Brian Cracknell
Sent: Monday, June 29, 2020 11:31 AM
Subject: [synchronomeelectricclock] Total Resistance In The Synchronome?
 
According to Mitchell's "Setting to Work" instructions the total resistance in the Synchronome is made up of of 8.7 ohms (main solenoid) and 2.45 ohms (pilot slave) giving around 11.15 ohms total. My Synchronome however (an early 1920s, apparently unfiddled-with one with the original green cotton still on the coils) seems to have a resistance of 7.00 ohms showing on the ohmmeter when the circuit is closed. This reading is also supported by the fact that my power supply shows 3.3 volts on the voltmeter and when I add a 3 ohm resistor (providing 10 ohms total resistance) I get the required 0.33 amp current showing on my ammeter.

So my question is, does anyone have a not-in-use Synchronome that can be checked to see what the resistance is on that?

And my other, key question: if it turns out that others do have the 11 ohms as Mitchell mentions, what can have happened to mine to make it be different? Looking at the wiring, one wire goes into the bottom coil and another wire comes out the top coil so they do both seem to be wired up.

Thanks
Brian 




Brian Cracknell
 

I have added photos of my clock to the Group Photos for general reference. The movement one shows the wire disappearing up behind the coils. There are no holes in the chassis in the normal place where the terminal would go for the armature jump lead.
Has anyone seen this arrangement before?


From: synchronome1@groups.io <synchronome1@groups.io> on behalf of John Hubert <jfphubert@...>
Sent: 30 June 2020 09:18
To: synchronome1@groups.io <synchronome1@groups.io>
Subject: Re: [synchronomeelectricclock] Total Resistance In The Synchronome?
 
I can’t explain why your clock appears to be different, but all clocks I have come across use the chassis - and in fact, the armature contact isn’t provided with any way of insulating it from the chassis.  I have never tried this - but I see no reason why you couldn’t run a small current (say 100 mA or less) through the system and use an iron item to check for magnetism at the two coils?  As I say, I’ve never tried it, but a low current shouldn’t cause any damage - and I would think would be detectable by ’the end of a screwdriver for instance.  Anyone tried this?

John

On 30 Jun 2020, at 09:11, Brian Cracknell <brcracknell@...> wrote:

John, I can't see any visible evidence of my clock using the chassis at all for the circuit. The jump lead from the armature does not visibly connect to the chassis - whereas the others I have looked at do connect to the chassis at a small visible terminal just above the armature spring. Instead, the jump lead disappears behind the coils to a hidden location - either to a chassis terminal there possibly or directly to something else. There is no sign of a terminal hole in the chassis at the normal location either. It is all very strange. The chassis doesn't seem like a very good conductor anyway - I checked for continuity at various points on it with the ohmmeter but it didn't manage to establish a circuit through the paint.
Brian


From: synchronome1@groups.io <synchronome1@groups.io> on behalf of John Hubert <jfphubert@...>
Sent: 29 June 2020 16:23
To: synchronome1@groups.io <synchronome1@groups.io>
Subject: Re: [synchronomeelectricclock] Total Resistance In The Synchronome?
 
To clarify, the top terminal connects to the gravity arm side of the switch.  Usually the connection  is a loop of wire.

The armature side of the switch connects to the chassis (some clocks have a small jump lead, others rely on the armature hinge).  This is the junction between the coils and the switch, both of which connect to the chassis.

The coils connect to the chassis at one end - and the lower terminal (two terminal clocks) at the other end.  The resistor is across the two series connected coils.  The junction point between the two coils is not connected to anything else.

Where a third terminal is fitted, it is connected to the chassis.  This was used when the clock was used with a Synchronome Distribution Board.

John

On 29 Jun 2020, at 15:43, Brian Cracknell <brcracknell@...> wrote:

Thanks John.

Hmm, doing this only shows open circuit (trying various places on the chassis to the terminal) whereas measuring between the terminal and the armature contact itself gives 4.5 ohms which I suppose makes sense given the 7 ohms overall including pilot dial. I will have to take the coils off and have a better look at the wiring in due course to check what is going on.

Regarding timekeeping, the clock can run for a couple of weeks or so with pleasing predictability and then for no obvious reason (ie no great change in pressure or temperature) it will suddenly switch to a gain or a loss of up to a second per day or greater and stay like that for weeks. I never adjust the thread on the bob and only ever add/remove small weights. 

One day it will run perfectly.

Brian


 
From: synchronome1@groups.io <synchronome1@groups.io> on behalf of John Hubert <jfphubert@...>
Sent: 29 June 2020 15:04
To: synchronome1@groups.io <synchronome1@groups.io>
Subject: Re: [synchronomeelectricclock] Total Resistance In The Synchronome?
 
The coils are indeed connected in series - and the (one) resistor is in parallel with the two series coils.  Its value is roughly 10x that of the coils.

The coils are connected to the chassis at one end (the one that goes to the contact on the armature) and to the (lower on most clocks, but centre on clocks with three terminals) terminal screw, so measuring between that terminal and chassis should give the resistance of the combination of the two coils in series with the parallel resistor.  IF there is a short to chassis at the point where the coils join - then you would only measure the resistance of one coil.

The electrical side would not of course vary the timekeeping, which should be typically a very few seconds a week or better.


John Hubert





On 29 Jun 2020, at 14:55, Brian Cracknell <brcracknell@...> wrote:

Hal, Ian, thanks for the replies. I did think the maths worked out a bit suspiciously as if only one coil was connected but how do I go about proving the function of either coil? The tails of those coils look very delicate so I am a bit hesitant to start poking around too much unless I have to. I would like to follow the wiring though but I am not sure what the flow of wires should be. The coils "input" wire from the bottom of the armature disappears under the lower coil and presumably connects into that wire-wound resistor that Ian mentioned which I can just see between the coils right at the back and then the flow must come back into the first coil again, thence to the second one - they are in series I take it? I can't seem to find a circuit diagram anywhere.

Both coils have two wires connected as far as I can make out in the tight space. If the bottom coil was broken I had assumed no current could flow through the whole circuit? (Unless it had been bypassed but I can not see that this is the case.)

By the way, the other movements I have looked at on the computer have the wire from the armature going into a hole through the movement plate below the lower coil, just above the armature return spring. My clock doesn't have that hole so presumably that was a change in design later on.

The clock works reasonably well but has never (in the 10 years I have owned it) kept time precisely. So I keep fiddling with it and this is just the latest anomaly I have noticed.

Brian


From: synchronome1@groups.io <synchronome1@groups.io> on behalf of H Hal via groups.io <haal@...>
Sent: 29 June 2020 13:23
To: synchronome1@groups.io <synchronome1@groups.io>
Subject: Re: [synchronomeelectricclock] Total Resistance In The Synchronome?
 
I will check mine when I get into the workshop.
 
In the mean time what jumps out for me is that your 7 ohms I presume is total resistance so your main solenoid has 7 minus 2.45= 4.55 ohms
 
now if one of the two main coils has failed (shorted) the main resistance would be half of 8.7 ie 4.35 with a little resistance from the shorted coil giving 4.55 ohms
 
 
in other words I would suspect one of the main coils to be wired incorrectly or shorted out
 
 
 
hal
 
uk
 
From: Brian Cracknell
Sent: Monday, June 29, 2020 11:31 AM
Subject: [synchronomeelectricclock] Total Resistance In The Synchronome?
 
According to Mitchell's "Setting to Work" instructions the total resistance in the Synchronome is made up of of 8.7 ohms (main solenoid) and 2.45 ohms (pilot slave) giving around 11.15 ohms total. My Synchronome however (an early 1920s, apparently unfiddled-with one with the original green cotton still on the coils) seems to have a resistance of 7.00 ohms showing on the ohmmeter when the circuit is closed. This reading is also supported by the fact that my power supply shows 3.3 volts on the voltmeter and when I add a 3 ohm resistor (providing 10 ohms total resistance) I get the required 0.33 amp current showing on my ammeter.

So my question is, does anyone have a not-in-use Synchronome that can be checked to see what the resistance is on that?

And my other, key question: if it turns out that others do have the 11 ohms as Mitchell mentions, what can have happened to mine to make it be different? Looking at the wiring, one wire goes into the bottom coil and another wire comes out the top coil so they do both seem to be wired up.

Thanks
Brian