Re: Total Resistance In The Synchronome?


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

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