JCM800 with new Metro Board Kit

[syscokid]

This is from my 82' JCM800 50watt Combo, #4104:

Here's the original PCB, right after I had Don Butler, aka Toneman, overhaul/plexi-speced this amp about 3 years ago:


Then about 3 months ago, I replaced all the carbon film resistors with these Vishay/Dale metal films, and did some rewiring on the old PCB and chassis.
Here we have a comparison with the "modified-old" and the new Metro board. Once again, I stuck with the metal films, and replaced the Xicon caps with the Spragues:


Tadaaaaaaaaa:

I think I need to work on cleaning-up on some of the wiring...especially the "alternative grounding" I've been trying. I just got through ordering a new PT from Marstran. Hopefully that will take care of this little humming issue, that gets pretty noticeable when I have the master volume from 4 on above. If the new PT doesn't do the trick, I'll at least have a new PT in the "old boy".

Suggestions?

[demonufo]

So you replaced all those top notch Piher Carbon Films, with Dale/Vishays?

And then built another PTP board using the same components?

Did you go PTP because you wanted it to be easier to mod, or some other reason?

I'm struggling to get a grip on what you're after here, especially after getting rid of those Pihers.

Heater wiring coming through the chassis from the PT is a little sloppy, and may improve the hum a little. In fact all the heater wiring could be improved on a little bit, but this was the worst area. It should be twisted nicely, not one wrapped around the other - that may in fact make things worse.

[syscokid]

Thanks demonufo...
At the time I decided to swap resistors, I didn't know the difference between a Piher and a Piper. Since Metro sells the metal film Vishay's, and I think Mojave Amps uses the Vishays, too...I thought that if those are good enough for Metro and Mojave, then they're good enough for my Frankenstien JCM. Besides, a lot of this amps original values have already been altered from the Toneman's overhaul: Filter Caps, resistors, other caps and also a new OT.

And yes:
The main reason for the PTP board was to make it easier to mod, or work on...
2nd reason: It gave me more experience and something to do ...
3rd reason: It looks cool. Well, at least I think so...

You're also right about the sloppy heater wiring from the PT to the first power tube. I just didn't have enough orange wire from the PT to work with. The hum has existed before the overhaul. In fact that hum was there from when I bought this amp at a Flea Market in the late 80's for $200.

Over this past weekend, I ordered a new PT from Marstran. And I am planning to do a better job with that heater wiring.

BTW, If you think I hacked my JCM...you should see what I did to my 1980 SG Standard...

[demonufo]

That's fair enough. I think you're right about the original overhaul, especially if the OT went. I wasn't impressed with the way those sozo's were fitted originally either. No excuses for not drilling the board from the underside and getting them to fit horizontally.
Personally I don't think Mojave using Vishay's is much of a good reason to use them, and George's sells them because of demand. Having said that, they're not bad, but a little stiff maybe. If you still have any of them Piher's left, it might be an idea to see if any will fit.
I'm not suggesting you extend the leads or anything like that though. It might be good enough electrically, but aesthetically ( )yuk.

To be fair, out of the 4 Marshalls that I've owned myself (there have been others, but none that I feel comfortable with calling them Marshalls ), I could never get rid of that last little bit of mains hum, although mine never increased with volume, it was always there in the background. Purely vibration of the transformers themselves as opposed to anything being amplified (well, there may have been a fraction getting through on the 2104 and the 1987, but never on my 4104 or 2204).

Nothing wrong with Xicon's either, BTW, but the Sprague's do look cooler. BC's even cooler still. Never known any fail on me as yet, although I have known older Sprague caps fail. Perhaps I'm not listening hard enough, but I can't detect any difference between the three in the bias circuit.