Valve Jr Fried?

[CJPreston]

Good day folks - So I am back after having some free time this evening to tinker. I have replaced R1 with a 1M resistor and R2 with a 10K resistor and removed JP1 and now I have no sound at the input...I figure I could undo what I've done and see if it works afterwards. I've tested continuity at the input and through the signal path and all has checked out. What would you folks recommend. undo it all and see if it works or perform some other tests and report back?

[Dave H]

I have replaced R1 with a 1M resistor and R2 with a 10K resistor and removed JP1 and now I have no sound at the input...

I'd replace JP1. I think the layout of version 1 is different from the later versions where snipping JP1 disconnects C3. You could remove C3 on version 1 if it has too much gain after the input resistor mod.

[CJPreston]

I'd replace JP1. I think the layout of version 1 is different from the later versions where snipping JP1 disconnects C3. You could remove C3 on version 1 if it has too much gain after the input resistor mod.

Thanks Dave -

I suspected that might be the case after tracing the signal path under the board. I could not locate JP1 on the schematic and wanted to trace it. I will plop it back in place this evening and we should have some magic.

[CJPreston]

I'd replace JP1. I think the layout of version 1 is different from the later versions where snipping JP1 disconnects C3. You could remove C3 on version 1 if it has too much gain after the input resistor mod.

Update: Dave that is where the disconnect was in the chain. Dropped it back in and there was some magic. A nice improvement to my ears with the R1 and R2 swaps. The next thing I think I will tinker with is removing the hum from the circuit and checking the voltages at V1 and V2.

I have to be careful...I've found myself tinkering with the amp more than playing here recently

[Dave H]

The next thing I think I will tinker with is removing the hum from the circuit

I have to be careful...I've found myself tinkering with the amp more than playing here recently

Add R10 and C9 from Version 2 schematic and change C6 and C9 to 47u. That will reduce PSU ripple by a factor of 10 (20dB)

My guitar has only been a signal generator for amp testing since my band broke up in 2008