OK Then

[Tone Meister]

Champ 5F1 circuit built for 1 watt output, duly notated inside the cabinet and inside the chassis by the power tube socket. Tested and verified that indeed it produces exactly 1 watt into reactive load. (2Vrms into 4 ohms)

I'd like to restore it back to stock but don't know where to start. Here is the relevant info:

>Mercury FTCP-59 power transformer
330-0-330, 6.3v no CT, 5v
>Mercury Tone Clone FTCHO-5 output transformer
single 4 ohm tap

>Rectifier is a good, strong Ken Rad 5Y3
315 VAC from the PT to rectifier (loaded)
350 VDC out to first filter cap
313 VDC at second cap
273 VDC at third cap

>6V6 Sylvania 6V6GT
Pin 3 - 338.5 V
Pin 4 - 313.8 V
Pin 8 - 18.5 V

>12AX7 RCA longplate
Pin 1 - 163.7 V
Pin 3 - 1.1 V
Pin 6 - 183.1 V
Pin 8 - 1.3 V

Filaments are getting 6.7 VAC on each tube. Trying to figure out where the builder reduced output power.

[The Dude]

There's only a handful of components in that thing. I'd just start left to right on the eyelet board and see what doesn't match the factory layout. Shouldn't take long at all.

[loudthud]

Verify that R8 is indeed 470 Ohm. Other than that I would need to verify the primary impedance of the output transformer. I think the stock OT has a 5K primary.

[eschertron]

What's the value of the NFB resistor?

Does your amp match one of the schematics posted? If so, which one? (they differ by a cathode bypass resistor on stage 1)

[Tone Meister]

There's only a handful of components in that thing. I'd just start left to right on the eyelet board and see what doesn't match the factory layout. Shouldn't take long at all.

Yeah, but it's not on a board, it's all point to point and the work is very sloppy. I did find a 220K from the 6V6 grid to ground that I'm wondering about. Wouldn't that limit curremt draw on the tube?

[galaxiex]

Yeah, but it's not on a board, it's all point to point and the work is very sloppy. I did find a 220K from the 6V6 grid to ground that I'm wondering about. Wouldn't that limit curremt draw on the tube?

That is the grid leak.

It's supposed to be there.

[Tone Meister]

What's the value of the NFB resistor?

Does your amp match one of the schematics posted? If so, which one? (they differ by a cathode bypass resistor on stage 1)

The V1 bypass resistor is 1K in this amp, not 1.5K. Also, the NFR is 1.4K and not 22K. R8 is indeed 470R.

[The Dude]

The other thing to look for would be series or parallel high wattage resistors in the OT secondary. It could just have built in power soak.

Edit: I was typing during your last post. If the NFB resistor is 1.4K instead of 22K, you'll need to change that. That's a lot of additional NFB.

[nosaj]

The other thing to look for would be series or parallel high wattage resistors in the OT secondary. It could just have built in power soak.

What is the value of the volume pot?

nosaj

[Enzo]

If the NFB resistor is 1.4k (and where did we get that odd value?) instead of 22k, then there is a tremendous increase in NFB signal. That will slow down a power stage. Just disconnect that resistor and see if the output grows.

[Tone Meister]

Just looked closely. No power soak resistor(s)

[Tone Meister]

If the NFB resistor is 1.4k (and where did we get that odd value?) instead of 22k, then there is a tremendous increase in NFB signal. That will slow down a power stage. Just disconnect that resistor and see if the output grows.

I measured it. I was thinking that measuring 1.4K is better than relying on the stripes for actual value, at least in this case. After all, we have a (deliberate) reduction in output power. I'll disconnect that NFR and report back.

[Tone Meister]

Peeled back the heatshrink and the NFR is 22K. Disconnexted it measures ok.

[The Dude]

If you upload a good pic or two, maybe somebody will spot something.

[Tone Meister]

If you upload a good pic or two, maybe somebody will spot something.

You asked for it, ha ha.