The Amp Garage

Can the bias circuit after the diode account for the low negative voltage? Sure. But the circuit in your schematic is good. Maybe your actual circuit is not wired the same as the schematic. Maybe the 100µF cap is installed backwards. Maybe the diode is installed backwards. Disconnect the 10K so the...

Change the 100nF to 47nF. Change the 33K to 56K. Replace the 1N4007. Your voltages should look like this...

Prior to installing the Hammond 261M6 did you ever use a different PT with a center tap connected to ground ***AND*** connected to a FWB rectifier as shown in the attached pic? If so, the two diodes circled in blue are now open. That will prevent you getting good bias voltage.

Raoul Duke wrote: ↑Tue Jun 11, 2024 12:37 pm No Sir, no crackle or strange sounds either static or while sweeping. I tried just to see if the pot was at fault, seems fine.

What I meant was does it affect the quality of the guitar sound?

Does this balance trimmer issue cause any sound issues?

jer_vic wrote: ↑Sun Jun 09, 2024 9:59 pm Can I join the two grounds (see attached diagram) together and solder them to the brass plate together, or do they have to be separate?

You can do that. It's not ideal, but then Dave Hunter's ground scheme is not ideal either. Probably not gonna make an audible difference in this simple amp.

Stevem wrote: ↑Sun Jun 09, 2024 11:07 pm The pin outs are not all the same .
A 6U10 and a 6D10 are not the same pin out.

They certainly are the same pin out

You start by securing a real schematic. Then you make your amp agree with that schematic.

The pin outs are the same.

Can you post the entire layout diagram rather than just a snippet?

Hakko has several lead forming tools. Here's one...

https://www.tequipment.net/Hakko/PNR-30-D/Pliers/?v=0

If not the correct one just search for electronic component lead forming tool.

Mark wrote: ↑Sat Jun 08, 2024 12:29 am

trobbins wrote: ↑Fri Jun 07, 2024 6:04 am What data were you assessing to come to that view ?

I’m not sure who the question is directed to.

Gotta be you since you're the only one to use the word "data" in this thread.

hebaton wrote: ↑Wed Jun 05, 2024 6:20 pm I am assuming the signal needs to be taken from the plates of V1b and V2B and fed to the grid of V3A ????

That's basically correct, but there is a lot of circuitry between the V1b/V2b plates and the PI grid.

https://sluckeyamps.com/phoenix/phoenix.pdf

The 5E7 is a 6L6 amp and the 5E9 is a 6V6 amp. I would expect the 5E7 power transformer to be larger. The Hammond replacement transformers agree. The 5E9 uses a 290BX with a bolt pattern of 2.25" x 2.831". The larger 5E7 uses the 290D2X with a bolt pattern of 2.75" x 3.438". https://www.hammfg.com/f...

Looks like the schematic is a different revision from the actual amp?