help me bringing a lowrider back to life?

[add4]

Hello guys and thanks for looking.

So i had a working, unboxed lowrider, and last year, i fried it up .. i don't even really remember what i did (never work on pedals under severe lack of sleep due to a newborn daughter..), but i know i plugged a bad PSU into it and then it was gone..
I can't remember if the bad PSU was : reverse polarity, AC, or too high voltage, i THINK it was AC.

anyway, i kind of stopped working on pedals for about one year, and now that i have a bit more free time i just dug up the remains of my loved lowrider and i'd like to bring it back to life..

Weird thing is that sometimes, when i manipulate the board, the voltages start to oscillate on almost all of it, impossible to measure anything.. so i guess time and out of the box manipulations made some kind of shortcut somewhere ... The voltages are then almost impossible to visualize on a multimeter
I notice that some ICs  (IC3 and IC4) have a clk input on the schematic so they might make that happen? or is that oscillation a sign of a problem somewhere?

[Thomas_H]

I would start this by removing all ICs from the sockets.

Then apply power and meassure voltages.

Maybe remove D7 and C22 first as they are gone for sure.
Repace them with new ones.

[add4]

Great !
I'll do that as soon as family is in bed, what should i check once that's done ?

[Thomas_H]

After replacing diode and cap meassure all voltage supply pins in the IC sockets for correct value (9v). Anything between 8.5 and 9.5 is ok.

If one is missing you should look for a fried trace.

If they are ok you could put in all the iCs at once and test the whole effect but i would take a little more time and follow the below:
Start adding ICs one by one and afterwards always meassure the supply voltage on ONE of the remaining iCs.

If the supply voltage is not ok after putting one in you can assume the IC defect.
Repeat until all sockets full 

[add4]

Thank you so much for giving me a battle plan, i'm taking the soldering iron now and see what i can do before sleeping ..

I'll keep you posted if i find anything .. or get it back to a functional state thanks to you!

[add4]

ok so,
removed the ICs, removed D7 and C22, replaced them, checked the power rails for all ICs, they are ok, plugged the ICs back in place on after the other,  no more fluctuations.
So i plugged the effect into an interface to my computer and crappy earphones and it's working! all octaves are here everything seems correct, but with that crappy amp, i couldn't hear much, but i was under the impression that i had a big volume loss when i clicked the effect in on my testing rig ... i'll have to do a test with an amp, hearable level, and try to track it down...

I already made a big step forward, thank you so much!
if anyone has ideas for a possible reason for volume loss, for all the octaves, don't hesitate to speak up

[Thomas_H]

Good job!

[add4]

Since I had already replaced d7 trying to fix that, I think it was c22 that was fried. That would make sense as it's there to stabilize the power rails and I had fluctuations in the voltages into all the circuit, wouldn't it?