OK Then

[The Dude]

I'm not as put off by the soldering as I am the wiring mess and "layout" (used loosely).

[g1]

I see one resistor there that was almost buried in heatshrink, which leaves the possibility that there are others completely covered.
I'm tending toward nosaj' suggestion of an attenuator there somewhere limiting the pre-amp signal prior to the 6V6 grid. Like a fixed PPIMV without the PI.
But I haven't checked into the OT yet, has anyone? LT mentioned checking on the primary impedance. Could a massive mismatch drop the power this much?

[The Dude]

The PT from post one is a Champ replacement, so no problem there. No part number given for the OT, so not sure. IMO, it would have to be an extremely gross mismatch to drop 5 watts to 1. It seems unlikely you would use a 6V6 and then some off the wall OT to drop wattage rather than just build a 1W amp with some smaller output tube and OT configuration. But, anything is possible.

[Tone Meister]

The OT is a Mercury FTCHO-5 which is a direct 5 watt Tweed F51 replacement

[g1]

Remove any lumpy heatshrink, there are resistors in there, who knows what else.

[Tone Meister]

Remove any lumpy heatshrink, there are resistors in there, who knows what else.

There it is, someone had to be THAT guy! Reckon that'll be my next move, just before I order an eyelet board.

[Chuck H]

Well it's a mess to try and diagnose by the photos for sure. But I can understand why you'd want to know what the wattage dropping mechanism is before rebuilding it. Because there's always that chance that your friend is going to say it sounds too different, he likes it less now and please make it the way it was

[eschertron]

Because there's always that chance that your friend is going to say it sounds too different, he likes it less now and please make it the way it was

Get a signed and notarized disclaimer that your customer *won't* want it the way it was. It'll likely sound 'different' even if the schematic matches exactly.

[Tone Meister]

Get a signed and notarized disclaimer that your customer *won't* want it the way it was. It'll likely sound 'different' even if the schematic matches exactly.

He wants it to sound different, even though it really does sound great at 1 watt of output. I have a Champ 5F1 build here with the same major parts as his putting out a little over 5 watts. He wants his to sound like mine. Ordering a board today and gonna look closer at the wiring before the 6V6 to see what I can find.

Most definitely I want to determine what's dropping the wattage, for my own knowledge base if nothing else. And who knows, someone may want a 1 watt 5F1 one day and I'll know exactly what to do, except much more neatly than what we have here. I'm no tech, but I most certainly know wire management and how to solder with the best of them.

[loudthud]

I think a blackface reverb transformer would drop the power somewhere near 1 W. Glad to see it got worked out.

[eschertron]

Yes. Keep us posted. I, for one, think a one-watt pentode (er, sorry, beam tetrode) design might be nice for the home or coffee shop.

[Tone Meister]

Well, this amp has 14 resistors total, and looking at Rob Robinette's layout, if you add two 100R for the false center tap, that would equal 14 resistors total, right? I have verified all the values as correct, according to Rob's layout attached. I don't see any extra resistors anywhere in the signal path.

It's a real mess, and as simple as it is, it's still difficult to suss out the actual layout.

[Helmholtz]

The 6V6 voltages look reasonable. What is the AC signal voltage at the 6V6 grid at full output? It needs about 13Vp or 9.2Vrms for ~5W output.

[nosaj]

Well, this amp has 14 resistors total, and looking at Rob Robinette's layout, if you add two 100R for the false center tap, that would equal 14 resistors total, right? I have verified all the values as correct, according to Rob's layout attached. I don't see any extra resistors anywhere in the signal path.

It's a real mess, and as simple as it is, it's still difficult to suss out the actual layout.

[ATTACH=CONFIG]52298[/ATTACH]

So is there any chance the 12ax7 is not producing the proper gain structure? What does a new 12ax7 do?

nosaj

[Tone Meister]

So is there any chance the 12ax7 is not producing the proper gain structure? What does a new 12ax7 do?

nosaj

It seems to me that you believe I'm claiming there is a problem with the amp, there isn't. Or maybe I'm just interpreting your responses wrong. The amp was originally built to produce 1 watt output and that it what it produces. The "builder" made a note inside the cabinet and another next to the tube socket (1 watt). The amp sounds just fine, the work is beyond shoddy, but the amp works and sounds fine and produces exactly 1 watt rms, as advertised.

The owner wants to find the intentional throttle-down point and restore it back to to 5 Wrms (4.5Vrms @ 4 ohms)