2 stroke/ Angela pse - hum but no guitar

[MWJB]

Your ohmeter reads "1/0.4/2.3" what? Ohms/kohms? Are you doing this power off? When you probe the ends of the cap feeding the volume control (vol set full up), you should be reading significant resistance.

[SWA]

Morning All

With, or without power, I'm getting 0.7 ohms between the volume pot end of the 2 caps & ground. Is this related to my earlier comment about the 100mv signal appearing at all 4 plates when in standby? Sorry but I just can't seem to get my old, but not overly experienced, head round this problem.

Thanks again for all help & support so far.

Cheers.

[MWJB]

0.7 ohms is a dead short, almost meter default when it sees no resistance at all (your meter won't read 0.00 unless it has a calibrate function).

Disconnect the wires to & from the volume pot, leave them hanging free. Now what do you read at the 2x 0.022 caps feeding & being fed from the volume pot? We are trying to see whether you have a problem pot or pot wiring here. Shielding the wires is good practice, but you have very short wire runs, for now I would just use plain wire to eliminate margin for error, when rewiring the vol pot.

If with the volume pot disconnected, you still read 0.7 ohms or just single (or even double) digit ohms rather than kilo ohms, then somehow, you have grounded these 2 caps.

[SWA]

Hi there & sorry for the delay in coming back.

I've disconnected all 3 pots & have a big fat, dead short-type 1 at both caps! I've checked the continuity from turrets to ground in that vicinity (thinking about solder 'tails' etc.) but have only had expected 'beeps' off the ground side of the grid leak & cathode resistors - still confused but perhaps closing-in on something dodgy at the junction of the 56k plate resistor & the 4.7nf cap? What's the expert opinion?

Thanks again.

[MWJB]

Whatever it is, it's on the side of the board that we can't see. What is the dc resistance from the top of the cap feeding tghe vol pot, to ground? Like wise the cap feeding V2 grid?

[SWA]

Hi & thanks for continuing to help.

Got '1' on both sides of both caps - powered-up or not. I've tried all the ohm range settings on my little AVO & the reading does not vary. Time to hook the board out?

You've identified many improvements along the way which I can incorporate if I have to rebuild but would you do anything else different circuit wise? Any else I don't need or might include or substitute? The amp is for my son who likes the tweedy Princeton vibe but requested less noise & a bit more body, refinement & a master volume. Essentially, I digested a dozen ancient schematics, read & re-read some favourite handbooks & arrived at what I believed would do the job - anywhere near? I have a tweed Deluxe cab ready plus a choice of Jensen P12R, Celestion G12H & Eminence Cannabis Rex for the young man to audition - just need to get a signal through!

Cheers for now.

[MWJB]

Yes, time to hook out the board.

"...but would you do anything else different circuit wise?" Ha ha! Yes, many things, but that's based on personal taste. I'm not sure why you have a grid leak cap on the input & second stage though? Your master volume doesn't need to be a voltage divider, rewire it as a variable resistor, just using the wiper & grounded tab to minimalise series resistance via the unused portion of the pot.

If, when you get the amp up & running, it sounds good to your son...then it is good, the end largely justifies the means.

[SWA]

Thanks MWJB - Today is building a new bathroom for my daughter & tomorrow is re-building an amp for my son! I'll let you, & other contributors, know how the amp goes but it'll probably be a few days.

All the best for now & have a great weekend.