Liverpool power supply (Ginger pics)

[PeteRH]

Great job Dana.
I have looked at that Ginger photo a dozen times and always took it for granted that the 25watt resistor was the 1K (suedo choke).....not a 125 ohm bias resistor. I never sat down and traced it out but the layout suddenly makes sense!!!

Looking at it with blurry eyes, I am guessing:
- The cap in the bottom right of the board is a 22mfd
- The three caps in the bottom of the cap stack are all 40mfd. These are all the same size in the top view.
- A red wire from the left hand side of the top 10K resistor appears to go right and then travels down to the 22mfd in the bottom left hand corner of the board. The red wire may actually go under the board to keep it away from the 1K and diodes???
- The junction of the standby switch and the 1K goes to two of the 40mfd caps in the stack. I can not make out a wire so this could be under the board.

This is just my guess.........those photos are pretty grainy.


Kens use of a spst switch for the 1/2 power works pretty well but has the disadvantage of running the same bias resistor values for 1/2 and full power. I used the matchless setup in my Liverpool clone where you can use a 62 ohm resistor for running all four valves or switch to a the 62 and 68 (or whatever) in series when running just the two. This enables you to adjust the bias to cater for the increased B+ when running only 2 valves.

Cheers
Pete

[UR12]

I have looked at that Ginger photo a dozen times and always took it for granted that the 25watt resistor was the 1K (suedo choke).....not a 125 ohm bias resistor. I never sat down and traced it out but the layout suddenly makes sense!!!

Looking at it with blurry eyes, I am guessing:

Yea, Blurry eyes, Crossed eyes and a magnifying glass. One quick note. The bias resistors are supposed to be 130ohm and not 125. I wasn't able to find a 130 ohm 10 and 25 watt resistor locally so I had my local counter guy measure about 2 doz with a meter until he found 2 125 ohm that measured 129.9 ohm. Sorry this is deceiving. I always measure any part I put on my boards. Things aren't always as they appear.

- The cap in the bottom right of the board is a 22mfd
- The three caps in the bottom of the cap stack are all 40mfd. These are all the same size in the top view.
- A red wire from the left hand side of the top 10K resistor appears to go right and then travels down to the 22mfd in the bottom left hand corner of the board. The red wire may actually go under the board to keep it away from the 1K and diodes???

It's good to have a fresh set of eyes on this. I can see the streak of red that you are refering to as far as the red wire coming from the top 10k resistor to the 22 mfd cap and that makes sense regarding all the bottom caps being 40 uf (the same size.

- The junction of the standby switch and the 1K goes to two of the 40mfd caps in the stack. I can not make out a wire so this could be under the board.

This is just my guess.........those photos are pretty grainy.

Yes it leaves the board on the right and then goes under the board an over to the 2 40uf caps that are paralleled. the other end of the 1k is a blue wire and connects to the 3rd 40uf. I have also changed the cap on the board to 20uf

Kens use of a spst switch for the 1/2 power works pretty well but has the disadvantage of running the same bias resistor values for 1/2 and full power. I used the matchless setup in my Liverpool clone where you can use a 62 ohm resistor for running all four valves or switch to a the 62 and 68 (or whatever) in series when running just the two. This enables you to adjust the bias to cater for the increased B+ when running only 2 valves.

I have looked at the DC30 but as you said Ken used a SPST switch and judging by the way the white wires come off the board and the blue wire connections from the switch to the board I am 99% sure that this is how Ken had it wired. I am trying more to document what Ken did instead of updating the schematic and layout for newer circuits. I am going to build Ginger to Ken's specs as close as I can get and then use it for a benchmark to compare my second Liverpool to. I used the 130ohm resistor as a starting point as this value is used in a bunch of el84 circuits. I would guess that the tubes back in 82 when Ginger was built were a lot better than we have now, so I can only speculate that the voltage increase on the tubes back then may have not been an issue. Todays tubes are a lot more unforgiving and I may have to go back later and use the dc30 style switch.
Thanks for the corrections Pete (Great eyes !!) I will update the layout this evening when I get home if you want to give it another look.

[UR12]

PeteRH

I have updated the wiring layout (pg1 of this thread) with your changes. Please give it a look and let me know if I got it right.

Thanks

[PeteRH]

Dana,
Now that you point it out, I can see that the red wire running under the board is from the 1K standby junction . I really think you have nailed it!!
Where's that emoticon for the thumbs up????
Cheers
PeteRH