Fender Stage Lead - Channel Switch and Intermittent Output

[misterc57]

I have a Stage Lead with intermittent channel switching and output. The physical switch on the front panel is good. Sometimes it stays on channel two regardless of position. Also there is hardly any output heard, but if I tap on IC6 it sometimes pops in loud and clear as it should be.

I checked all solder connections in that area. They looked good but I reflowed some. This did not fix anything.

I suspect I need to replace IC6 (TL06). Do you think this IC would cause both issues I am seeing?

Schematic attached.

Thank you, MC

Fender_stage_lead.pdf

[52 Bill]

Have you cleaned and tested the footswitch jack?

[Enzo]

Anything is possible, but it is way more likely you just have a bad footswitch jack.

Look at your schematic, find the panel switch. top center area. See where it is wired in series with the jack? If those contacts get dirty or bent, then the switch circuit is not complete.

When you tap on IC6, you are also tapping very close to P4 connector. Note the footswitch is wired to that connector. SO instead of the jack itself, we could also have solder or contact issues with pins 1 and 2 of that.. Also points E3 and E4 are the wiring points for the wires to the panel switch. They are also right there beside IC6. And either of those connections could be loose.

Could IC6 be bad? Sure, but in my experience, in general ICs don't get physically intermittent inside.


And TL06? Perhaps TL604?

[misterc57]

You got me to focus on the jack and I found the problem to be the harness from the foot switch jack where it connects to the board.

Moving those wires at that point was causing the intermittent issues. I reflowed the 6 pins for the harness on the board and the issue seems to be gone.

Thank you!

[misterc57]

Now that the intermittent problems are resolved I discover a problem with the reverb. There is a ghost wind like noise when turning up the reverb. I tried a different tank and the same issue.

Noisy ICs? Suggestions on how to diagnose?

Thank you, MC

[Enzo]

ICs are cheap, you could swap in a new one in a couple minutes and find out.

[misterc57]

IC7 is a 4558 which I do not have. Can I swap a TL072 in its place? I have seen some comments on line that say yes but also some who advise against it.

Thank you.

[misterc57]

I found a 4558 and replaced IC7. Reverb works fine now. Thank you!