Tube Screaming Ultra – doesn’t work (solved)

[Guilherme]

Hello, I have tested continuity between all soldered components (including pots, jacks and switches). The board powers up and the LED light up.

The sound is only available when bypassing the board.

I post some pictures, maybe some one can help troubleshoot? thank you

[Barry]

I cannot accurately follow the In and Out wiring (white wire) in any of the photos.

This is the best photo I see, but it’s inconclusive.

 

I also cannot see where you have common ground connecting the main board with the 3PDT wiring board. You can check for continuity between both PCBs by using any of the extra ground pads on each.

I see ground from power jack to main board but nothing from main board connecting to the wiring board, or alternatively from the main board to the In and Out Jacks, then to the wiring board. 6 and 1/2 dozen.

If there is no continuity then your problem may be as simple as to use any extra ground on the main board and connect it to any extra ground to the wiring board. That is why there are extra to accommodate multiple wiring styles.

 

For reference here is the wiring layout in the build doc. I am not suggesting you need to completely rewire identically however you will note the single grey wire connecting the main board and wiring board.

 

All of that said if you do have continuity by some means I am not seeing then the next suggestion is to do a re-flow in some spots. Let me know and I will make some suggestions.

[Guilherme]

Thank you Barry,

Here are my comments and a photo with both Tube Screamer and 3PDT boards in same shot:

1 – in and out of screamer board are connected to BI and BO of 3PDT respectively

2 – power goes directly to 3PDT boards and the twisted black/red wires feed the screamer – I tested continuity of common ground in between the 3PDT board and the ground hole next to In and Out of Screamer (the ones besides I/O that have a gray wire to the jacks in the drawing you posted.

3 – I tested power and ground continuity from many different locations (power plug to 3PDT to main board) successfully.

4 – I did some reflow, I have a damaged solder pad, the yellow wire in the tone control (green wire in your sketch) –  I tested the continuity between the tone pot P2 and the following components successfully – C6, R8 and R11. SO I don’t think this is the problem.

Thank you for your comments and I appreciate any further help.

[Guilherme]

One more thing, when I put Tone up to maximum value, I hear a noise in the amp (something like a bug in the forest).

I tested the oscilloscope función of my multimeter and this is the output. I guess I can try to follow the signal chain like this, right?

 

[Barry]

An audio probe would make quick work of finding the problem.

Audio Probe

I could suggest carefully examining for loose wire connections. Sometimes moving things around wire connections quickly become broken or loose. It just takes one. If something is hanging by a thread, redo it.

You could also check your IC and transistor voltages.

[Guilherme]

Hello Barry, I found the problem, my 4558D Op amp was fried. I replaced it and it worked,

thank you.

[Author]

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