Homebrew HELP!

[lexluthier72]

He Gave me a couple more things to try....Change the type of volume pot, shield the 1st 12ax7. None of it cured the problem, and ultimately with we are going to re-do the layout into a turret board. I will post pics when I get further. Thanks for all the support
-E.

[hasserl]

As someone else pointed out, you really need to trace out all the wires and either draw out a schematic, or if this actually is a Pro Jr circuit, compare how it is wired up to the Pro Jr schematic. Right now all you've got is a bundle of wires that is really hard to make heads or tails out of. YOu said it's a homebrew amp? Really? Or is it an old amp that maybe someone has done some rewiring on?

If the volume control doesn't shut the volume down all the way, then it is probably not acting as a voltage divider, but more as a variable resistor, indicating there isn't a clear path to ground from the pot. Sort out the signal path and make sure the pot is wired correctly.

As far as how to mate the layout you found to this amp, the first thing you'd do is gut this amp and clean it all up. Start with a clean sheet, design the layout into the chassis that you have, then build the darn thing.

[lexluthier72]

Hasserl....Thanks for the reply. The conclusion Ive come to is to gut the amp. The problem is signal bleed from the 1st preamp stage, which from the homework Ive done is incurable in the amps current state. The lead dress/shielding is not correct. I have decided to gut the amp. Like I said in the previous post. I got a hold of the guy that did the layout I posted. He is going to help if I hit a snag, but ultimately this will be reworked into a turret style layout. Again, thanks for all the suggestions. I will post some photos as I get further into the rebuild.
-Erin

[lowell]

as far as volume goes... it seems to me that when you touched it you completed the ground on the volume pot thus allowing the signal to go to ground and "turn down." have you measure the resistance of the ground "lug" on the volume pot to the chassis? maybe it's a bad ground solder joint...??? just an idea, good luck.

[lexluthier72]

Thanks for the response. I have measured the resistance, and it does zero, but the signal does not.
-Erin

[lexluthier72]

Progress!

Hey all,
Tonight I got the chassis and the board stripped and ready for the new layout. I left the rectifier, the heater, and the OT wiring intact. I plan to clean up the fuse/power wiring as well....heres the progress so far....

[lexluthier72]

A couple more progress shots of the rebuild.....

[PRNDL]

That's beginning to look like a very professional build!

Some suggestions:

Mount the fuse on the chassis.

Get a faceplate. The easiest would be a copper plate that you can get at Ace Hardware. You can then mount power & standby switches and the input jack onto the front.

Actually, on my build, we put the face on the back, because it didn't have those holes. It might also be possible to put them on the existing faceplate, if there's room.

[lexluthier72]

For those of you who are staying tuned....Minor Progress...

All the power resistors mounted on the can cap. Grid stoppers mounted and wires run to power tubes. Cathode Bias jumper and resistor installed. Power cord and fuse holder cleaned up. All jumpers added to rear of board...More to come.
-Erin

[cgiff]

Twist,
Nice job on the boards. Cgiff

[lexluthier72]

For those of you still tuned in....more progress....The board is wired in. Unfortunately all I had was brown and gray wire for the tube sockets...a little hard to see over the brown heater wiring. Any comments/suggestions welcome.
-Erin

[Robert M. Martinelli]

volume pot wiring?

Hi,
maybe it' s a silly question, if so I beg your pardon, but sometimes we like to complicate our lives ourselves and we overlook the simple things : Have you checked the way the pot is connected? does the right lug go to ground? If this is not the case, then the pot is only acting as a variable resistor and not as a voltage divider, so even with the volume fully to zero some signal passes through it and reaches the following stage. With the right lug soldered to ground and the wiper fully down ( = to ground too ) there is no way signal can be still around....unless you have a gnd problem.
Hope this helps
Regards
Bob