Tommy III - hums and squeals

[Better Button]

Morning All.

Any assistance gratefully appreciated.

The build works in by-pass mode, and the LED lights, but all I get is lots of hum and squeal, increasing with gain.

My soldering skills are quite good and I have a general knowledge of parts etc, but can't read the schematic to any degree.

I've confirmed the voltage at the obvious points, and also at Pins 4 and 8 of the TL072.

I've checked the 3PDT, I / O, and all ground points for continuity.

I've reflowed the whole PCB, including underneath the bottom 2 pots.

Apart from the hums and squeals, touching the enclosure, or other metal parts has an effect on the hum, like there's a grounding problem, but I can't find it.

Again, thanks for any help.

Glen

 

[Locrian99]

Morning All.

Any assistance gratefully appreciated.

The build works in by-pass mode, and the LED lights, but all I get is lots of hum and squeal, increasing with gain.

My soldering skills are quite good and I have a general knowledge of parts etc, but can't read the schematic to any degree.

I've confirmed the voltage at the obvious points, and also at Pins 4 and 8 of the TL072.

I've checked the 3PDT, I / O, and all ground points for continuity.

I've reflowed the whole PCB, including underneath the bottom 2 pots.

Apart from the hums and squeals, touching the enclosure, or other metal parts has an effect on the hum, like there's a grounding problem, but I can't find it.

Again, thanks for any help.

Glen

Have you tried putting r5 in. I dont really think it would cause the issue but

 

[Better Button]

Yes, I wondered about R5. I read here that in lieu of an a25K pot for VOL, a 10K log pot could be used, omitting R5, which is what I did.

Glen

 

[spi]

Did you reflow the middle pin on the A500K jack. That one looks suspect, but could just be the picture.

What's up with the clipping switch. Mounted on the opposite side of the board?