First D-style (102) build opinions solicited & build thread:

[Raoul Duke]

I’m a big fan of risk mitigation, lol.

How would I test the PS nodes to ground?

[martin manning]

Just clip the black DMM probe to ground and then probe each of the B+ eyelets. You should see 10's of thousands of ohms at all of them.

[Raoul Duke]

Yes, that all went as you said it should

I’ll set some stuff up and see how it goes with the limiter.

[Raoul Duke]

Ok, got sound with the limiter, but…

The FET is “splatty”
No OD

Tone controls & tone switches all seem to work.

Time to take it off the limiter?

[martin manning]

Yes, I think you can remove the limiter, and then do the voltage survey. That should give some clues as to what isn't right about the OD and the FET.

[Raoul Duke]

That’s more like it!

Off the limiter:

V1A plate - 207
V2A plate - 215
Little higher than the layout, is that bad?

OD works fantastic!
FET sounds good with my LP, even better with a Tele or Strat.
Noise floor is pretty low with all the volumes up and no signal coming in. Like nothing at all from 5 feet away.
Hell, even that f’in’ footswitch that gave me so much trouble works as it should.
LNFB switch works, no pop.
This thing is LOUD.

I’m blown away…

[martin manning]

I don't know why you weren't getting the OD and FET when on the limiter, but it sounds like it's working fine. You are only a few volts high on the V1 and V2 plates so I wouldn't be too concerned at the moment, but you can tweak the dropping resistor ahead of the PI filer (the 2k7 on the power supply board). How about the FET voltages at the top and bottom of the 10k drain resistor?

Post all of the supply node voltages and the PI and preamp plate voltages.

[Raoul Duke]

On the limiter, the preamp tubes were barely lit. I still had the 40w bulb in, maybe that made the difference?
Sounds pretty good now

Would a 3k dropping resistor be better? What am I risking by leaving it?

V1A - 208
V1B - 211
V2A - 215
V2B - 225
PI A- 295.7
PI B- 289

Top of the 10k is 11.9
Bottom is 21.4

B+1 - 481
B+2 - 481
B+3 - 458.7
B+4 - 348.4
B+5 - 340.9

[martin manning]

B+1 is higher than the layout (just about where it was with only the power amp running), so that will propagate on down the line. Things might drift a bit, check your bias. If it stays where it is I would go up on the 2k7, maybe 3k3 for a start. Preamp voltages have an impact on tone, and I would try to lower them 10V or so.

[Raoul Duke]

Understood

That’s a 5w there I believe right?

[martin manning]

That’s a 5w there I believe right?

Yes, but you could get by with less, 1W even.

[Raoul Duke]

Well I’ve got a bunch of 3w in the range of what we’re talking about, so if those will work - I’ll start swapping and measuring.

I really appreciate all your help Martin! Learned a lot thanks to you!

I also appreciate everyone who took time to give me advice and suggestions! Looking back through the thread, I see this really is a “community” of enthusiasts who give of themselves quite generously. Thanks all!

Not done yet - but getting close

[martin manning]

Ok, cool. It might well take a 3k9.

V1A - 208
V1B - 211
V2A - 215
V2B - 225
PI A - 295.7
PI B - 289

Top of the 10k is 11.9
Bottom is 21.4

B+1 - 481
B+2 - 481
B+3 - 458.7
B+4 - 348.4
B+5 - 340.9

Note you had 488 B+1 biased at 39.8 (V5) and 39.5 (V4) mV with just the power amp running, so it has only come down 7V (1.4%) with the preamp and FET added.
Adjust the 2k7 to get the V1A plate down to 200V or just under.
Recheck the bias.
See where the FET ends up before deciding to do anything with that.

[Raoul Duke]

Will do. I have a few here I can try and a Mouser box due in on Tuesday.

The FET sounds decent, but probably not optimal. What am I looking for at the 10k?

[martin manning]

The FET sounds decent, but probably not optimal. What am I looking for at the 10k?

See the latest .pdf on biasing the FET in the files section. With the lower voltage at around half of the higher one you have a relatively clean boost. Bringing the lower voltage down further (hotter bias) adds distortion. You're on the cold side now.