Topics

19 set psu


MikeDavidsohnG3ZCC
 

Hi everyone
Hope you are keeping safe and well.
My19 set mk 3 renovation going well, it had a bad meter so have sourced another.
Preparing a psu to be fitted in the space where the B set was.
A question, the transformer has 4 secondary windings.
12 volt 100 volt 275 volt and 425 volt.
When wiring the HT2 circuit I have a sutable bridge rectifier that I can use and also have a couple of 30uf 600v wkg Caps.
Am I right in thinking that I connect the negative to the minus ht2 and of course the positive to the plus ht2.
With no earth connection to the circuit at all?
The 425 volt winding does not have a centre tap.
Also I want to add a 150k 2 watt resistor as a bleed across the smoothing capacitors.
I would very much appreciate some advice.
Thanks in advance.
73
Mike
G3ZCC


Chris_Suslowicz
 

Mike (G3ZCC) wrote:

Hi everyone
Hope you are keeping safe and well.
My19 set mk 3 renovation going well, it had a bad meter so have sourced another.
Preparing a psu to be fitted in the space where the B set was.
A question, the transformer has 4 secondary windings.
12 volt 100 volt 275 volt and 425 volt.
Check the 12 volt output doesn't get too high on load: 10% overvoltage reduces valve life by up to 50% (because the filament temperature is proportional to the 4th power of the voltage).

All the valves are indirectly heated types so should be OK on an AC supply - the relays may buzz a little and you may get hum pickup because the set was designed for DC. I'd probably rectify, smooth, and stabilise it if there was room in the set for extra bits.

When wiring the HT2 circuit I have a sutable bridge rectifier that I can use and also have a couple of 30uf 600v wkg Caps.
Those may be a little on the low side, voltage wise, as with the set on receive HT2 will rise to peak voltage - around 600.95 (ok, maybe not), but if you stack the 100V secondary in series with that (as the WS19 PSU supplies 490 - 540 volts according to specification/input voltage variation) it will definitely be too high.

Am I right in thinking that I connect the negative to the minus ht2 and of course the positive to the plus ht2.
With no earth connection to the circuit at all?
There's a bleed resistor in the dynamotor supply from HT2- to chassis in the British supply unit of 100k ohms decoupled by 0.1uF; the Canadians do not appear to have bothered with this, unless it's incorporated in the set.

The 425 volt winding does not have a centre tap.
Also I want to add a 150k 2 watt resistor as a bleed across the smoothing capacitors.
Bleed resistors are always good, you'll need about 5 watts worth that can stand 600+ volts.

Best regards,
Chris. (G8KGS)


john spendlove
 

You could put a rectifier in series with the relay coil and an electrolytic across both coil terminals for a bit of smoothing.Thats what I did back in the 60s worked well
          G4DXY


On Wednesday, 25 November 2020, Chris_Suslowicz <chris@...> wrote:
Mike (G3ZCC) wrote:

>Hi everyone
>Hope you are keeping safe and well.
>My19 set mk 3 renovation going well, it had a bad meter so have sourced another.
>Preparing a psu to be fitted in the space where the B set was.
>A question, the transformer has 4 secondary windings.
>12 volt 100 volt 275 volt and 425 volt.

Check the 12 volt output doesn't get too high on load: 10% overvoltage reduces valve life by up to 50% (because the filament temperature is proportional to the 4th power of the voltage).

All the valves are indirectly heated types so should be OK on an AC supply - the relays may buzz a little and you may get hum pickup because the set was designed for DC. I'd probably rectify, smooth, and stabilise it if there was room in the set for extra bits.

>When wiring the HT2 circuit I have a sutable bridge rectifier that I can use and also have a couple of 30uf 600v wkg Caps.

Those may be a little on the low side, voltage wise, as with the set on receive HT2 will rise to peak voltage - around 600.95 (ok, maybe not), but if you stack the 100V secondary in series with that (as the WS19 PSU supplies 490 - 540 volts according to specification/input voltage variation) it will definitely be too high.

>Am I right in thinking that I connect the negative to the minus ht2 and of course the positive to the plus ht2.
>With no earth connection to the circuit at all?

There's a bleed resistor in the dynamotor supply from HT2- to chassis in the British supply unit of 100k ohms decoupled by 0.1uF; the Canadians do not appear to have bothered with this, unless it's incorporated in the set.

>The 425 volt winding does not have a centre tap.
>Also I want to add a 150k 2 watt resistor as a bleed across the smoothing capacitors.

Bleed resistors are always good, you'll need about 5 watts worth that can stand 600+ volts.

Best regards,
Chris. (G8KGS)






AllanIsaacs
 

For sets that were designed for DC valve heaters I use the LT1083 regulator
which comes as a complete kit for AC to DC (although the heatsink is a bit
puny) for a little over a fiver from the usual place.
It's good for the T1154/R1155 valve heaters/relays, and any low voltage
requirement.
Allan G3PIY

-----Original Message-----
From: wireless-set-no19@groups.io [mailto:wireless-set-no19@groups.io] On
Behalf Of Chris_Suslowicz
Sent: 25 November 2020 11:22
To: wireless-set-no19@groups.io
Subject: Re: [wireless-set-no19] 19 set psu

Mike (G3ZCC) wrote:

Hi everyone
Hope you are keeping safe and well.
My19 set mk 3 renovation going well, it had a bad meter so have sourced
another.
Preparing a psu to be fitted in the space where the B set was.
A question, the transformer has 4 secondary windings.
12 volt 100 volt 275 volt and 425 volt.


MikeDavidsohnG3ZCC
 

Thanks, I will check out the regulator  had already decided to use dc volts.
Regards
Mike
G3ZCC


MikeDavidsohnG3ZCC
 

Sounds a nice easy way to do it.
Thanks 
Regards
Mike
G3ZCC


MikeDavidsohnG3ZCC
 

Thanks for the info Chris, I thought that I did read somewhere that the ht2 minus was floating.
I will add 5 watts of 150k from the ht2 minus to earth as in the dynamite.
Makes me happier with one in place.
Regards
Mike 
G3ZCC


MikeDavidsohnG3ZCC
 

Thanks again everyone for all the help and suggestions.
I expect the replacement meter here by next Monday and I will crack on with the psu in the meantime.
By the way the transformer is out of a scrap KW 204 transmitter, it will add a bit more weight to the 19 set.
Looking forward to firing it up.
Kind Regards
Mike
G3ZCC


Michael O'Beirne
 

Allan

What are the voltage and current limit specs for that LT1083 regulator kit
please?

Not now but later, when other repair tasks have been completed, I intend to
build a DC PSU for my C12. Stupidly it was stored for a couple of years in
a basement and the PSU became hopelessly damaged. In any event the noise of
the motor-generator would have been excessive on transmit. I still recall
using one at school.

73s
Michael
G8MOB

-----Original Message-----
From: wireless-set-no19@groups.io <wireless-set-no19@groups.io> On Behalf Of
AllanIsaacs
Sent: 25 November 2020 12:12
To: wireless-set-no19@groups.io
Subject: Re: [wireless-set-no19] 19 set psu

For sets that were designed for DC valve heaters I use the LT1083 regulator
which comes as a complete kit for AC to DC (although the heatsink is a bit
puny) for a little over a fiver from the usual place.
It's good for the T1154/R1155 valve heaters/relays, and any low voltage
requirement.
Allan G3PIY


Hawkeye
 

Hello Alan,

A look at the datasheet of the LT1083 tells that these regulators do a good
job at ripple rejection:
with Vin-Vout >= 2Volt the rejection is 70(80) to 30 dB at frequencies of 30
c/s to 100 kc/s.
so they may kill a lot of mains interference.

I do have somewhere info on replacement C-L-C mains filters with voltage
regulators!.
If it is of interest to you, I will come back to you.

-----Oorspronkelijk bericht-----
Van: wireless-set-no19@groups.io <wireless-set-no19@groups.io> Namens
AllanIsaacs
Verzonden: woensdag 25 november 2020 13:12
Aan: wireless-set-no19@groups.io
Onderwerp: Re: [wireless-set-no19] 19 set psu

For sets that were designed for DC valve heaters I use the LT1083 regulator
which comes as a complete kit for AC to DC (although the heatsink is a bit
puny) for a little over a fiver from the usual place.
It's good for the T1154/R1155 valve heaters/relays, and any low voltage
requirement.
Allan G3PIY

-----Original Message-----
From: wireless-set-no19@groups.io [mailto:wireless-set-no19@groups.io] On
Behalf Of Chris_Suslowicz
Sent: 25 November 2020 11:22
To: wireless-set-no19@groups.io
Subject: Re: [wireless-set-no19] 19 set psu

Mike (G3ZCC) wrote:

Hi everyone
Hope you are keeping safe and well.
My19 set mk 3 renovation going well, it had a bad meter so have sourced
another.
Preparing a psu to be fitted in the space where the B set was.
A question, the transformer has 4 secondary windings.
12 volt 100 volt 275 volt and 425 volt.


AllanIsaacs
 

Hi Michael
I covered the LT1083 in this page if you scroll down to "Experiments with
the LT1083"
http://www.radiomuseum.co.uk/power%20supply.html
I probably would have done better if I'd read everything before
experimenting with it!
Because of the high current rating, which I was aiming at, everything in the
circuit is important. For example if I'd used a decently rated 8 amp low
tension winding instead of cobbling together what was immediately at hand no
problem.....
For example 8A and 1 ohm gives a loss of 8 volts.
Raising the input voltage to cover losses at max current is OK but of course
the heatsink at half the current gets jolly hot.

The cheapo kit that pops up on ebay reveals

Technical specifications:
board size: 74mm x 46mm;
DC Input: 2.5 V-38 V;
Input AC: 2.5 V-27 V;
DC output: 2.5 V-35 V;
maximum current: 7A;
inlet and outlet pressure differential minimum: 2.5 volts;

Allan G3PIY

-----Original Message-----
From: wireless-set-no19@groups.io [mailto:wireless-set-no19@groups.io] On
Behalf Of Michael O'Beirne via groups.io
Sent: 25 November 2020 13:21
To: wireless-set-no19@groups.io
Subject: Re: [wireless-set-no19] 19 set psu

Allan

What are the voltage and current limit specs for that LT1083 regulator kit
please?

Not now but later, when other repair tasks have been completed, I intend to
build a DC PSU for my C12. Stupidly it was stored for a couple of years in
a basement and the PSU became hopelessly damaged. In any event the noise of
the motor-generator would have been excessive on transmit. I still recall
using one at school.

73s
Michael
G8MOB


Jacques_VE2JFE
 

Hello Mike,

 

The minus HT2 is not “floating”: it is connected to R16A which have it’s other side connected to GND.

No need to have another resistor added there if you build your supply into the set itself.

Using a bleeder resistor across the HT2 is not only a good idea, but a mandatory safety measure.

 

73, Jacques, VE2JFE


Jacques_VE2JFE
 

Hello Chis,

I am sorry, but when you wrote: All the valves are indirectly heated types so should be OK on an AC supply

Well, on a British MkIII set, not really: the filament supply HAVE TO BE DC, because the PYE designers used the LV supply to modify the bias of the BFO oscillator (V2B) On transmit and receive.

See how R10A (1K5)  is connected !!

BTW, if ever R10A is removed, the BFO no longer works in receive….

Don’t ask me how I know…

 

73, Jacques, VE2JFE


Hawkeye
 

Hello Allan,

Further to my remarks on the LT1083, I have found some info on the LR8,
which is a high voltage
adjustable regulator that can be used to replace filter chokes in
HT-supplies.

More info can be found here: http://www.pbpix.com/radio/lr8n3.pdf and
also
here https://wtfamps.com/2018/10/17/the-lr8-in-tube-circuits

Maybe you can use some of the info for building HT-supplies

Best regards,

Cees



-----Oorspronkelijk bericht-----
Van: wireless-set-no19@groups.io <wireless-set-no19@groups.io> Namens
AllanIsaacs
Verzonden: woensdag 25 november 2020 17:25
Aan: wireless-set-no19@groups.io
Onderwerp: Re: [wireless-set-no19] 19 set psu

Hi Michael
I covered the LT1083 in this page if you scroll down to "Experiments with
the LT1083"
http://www.radiomuseum.co.uk/power%20supply.html
I probably would have done better if I'd read everything before
experimenting with it!
Because of the high current rating, which I was aiming at, everything in the
circuit is important. For example if I'd used a decently rated 8 amp low
tension winding instead of cobbling together what was immediately at hand no
problem.....
For example 8A and 1 ohm gives a loss of 8 volts.
Raising the input voltage to cover losses at max current is OK but of course
the heatsink at half the current gets jolly hot.

The cheapo kit that pops up on ebay reveals

Technical specifications:
board size: 74mm x 46mm;
DC Input: 2.5 V-38 V;
Input AC: 2.5 V-27 V;
DC output: 2.5 V-35 V;
maximum current: 7A;
inlet and outlet pressure differential minimum: 2.5 volts;

Allan G3PIY


Chris_Suslowicz
 

Jacques (VE2JFE) wrote:

Hello Chis,
I am sorry, but when you wrote: All the valves are indirectly heated types so should be OK on an AC supply
Well, on a British MkIII set, not really: the filament supply HAVE TO BE DC, because the PYE designers used the LV supply to modify the bias of the BFO oscillator (V2B) On transmit and receive.

Argh! (I thought I knew how these sets were put together.) :-(>


See how R10A (1K5)  is connected !!
BTW, if ever R10A is removed, the BFO no longer works in receiveŠ.

(sigh) Something new every day. :-(>

Don't ask me how I knowŠ

Broken or open circuit resistor, I would guess.

Best regards,
Chris. (G8KGS)


AllanIsaacs
 

-----Original Message-----
From: wireless-set-no19@groups.io [mailto:wireless-set-no19@groups.io] On
Behalf Of Hawkeye via groups.io
Sent: 25 November 2020 17:24
To: wireless-set-no19@groups.io
Subject: Re: [wireless-set-no19] 19 set psu

Hello Allan,
Not used one of those Cees, but not bad at only 45p
Allan G3PIY


Further to my remarks on the LT1083, I have found some info on the LR8,
which is a high voltage
adjustable regulator that can be used to replace filter chokes in
HT-supplies.

More info can be found here: http://www.pbpix.com/radio/lr8n3.pdf and
also
here https://wtfamps.com/2018/10/17/the-lr8-in-tube-circuits

Maybe you can use some of the info for building HT-supplies

Best regards,

Cees


Jacques_VE2JFE
 

Hello Chris,

 

To my last comment, you wrote: Broken or open circuit resistor, I would guess.

No, worse than that… I got my first 19 MkIII in 1969 and it was a British E.K,Cole.

No proper schematic available anywhere for me at that time, so I relied on the Canadian MkIII user manual.

Because the B and I/C sections were of no use for me, I decided to remove them.

The plan was not really to build a PSU in the “liberated” space, but…

The R10A is mounted within the B set area, so figure what I’ve done….

It took me five years to put my hand on another British MkIII set (a PYE) and then I was able to figure out why the BFO was no longer working in the E.K.Cole…

I still have those two sets (and many others) !

 

73, Jacques, VE2JFE


MikeDavidsohnG3ZCC
 

Thanks for that Jacques, 

I assume that resistor is on the large tagstrip to the right of the 807.

Thanks

Mike

G3ZCC


MikeDavidsohnG3ZCC
 

HI Jacques just checked and it reads nothing to earth on  R/T or MCW but a short on CW.

Removed everything except the brown wire from the tag (I assume that goes to the system switch) and it's the same readings.

I will fit a 1.8K to earth from the ht2 - line but not sure why there is a short on the CW setting.

Regards

Mike 

G3ZCC


MikeDavidsohnG3ZCC
 

Addendum for Jacques.

It seems that when in the CW position  the switch does indeed go to ground shorting out R16A.

I have fitted the resistor now, didn't have a 1.8K so put 2x 3.3K  2W in parallel (checks as 1.65K) and that sorts the problem there.

Would you put the HT2 bleed resistor from + to earth or across the HT + and - lines?

Regards
Mike
G3ZCC