Fixing an RV-5?

[Pepe]

Zener diode?

[laurie]

Zener diode?

Unlikely - the 3.3V regulated supply is working.

Let me ponder this a little more.

[sirlemonhead]

Thank you

I ordered that scope kit earlier so should have it in a few days.

[laurie]

Perhaps:
1) check for signal on pin 7 of IC2, and pin 7 of IC1. They both should have input signal on them irrespective of the settings on the pedal.
2) check for signal on C41 (either leg) and R36 (either leg). Try switching it with the treadle.

[sirlemonhead]

Signal is present on IC2 and IC1 on pins 7 and also 1.

I also get signal on either side of C41 before and after pressing the treadle.
I get no sound at all from R36 before and after pressing the treadle

[laurie]

OK... so basic power and analog signal paths are working.

Unfortunately... the blocking of the signal between C41 and R36 means the FETs aren't being switched. And they are directly controlled by output lines on the CPU chip. So the CPU isn't running.

Let's check the RESET circuit. What DC voltage do you see on pin #4 of IC9 ?
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SOT-23-5.jpg (83.18 KiB) Viewed 9260 times

[sirlemonhead]

3.3v on pin 4

[laurie]

OK. So that's not a problem - this was a check to see if the CPU and AD/DA were in hard reset mode all the time.

Let's just confirm there is no audio signal on pin #16 of IC8 (there almost certainly won't be... just want to confirm).

If no signal on pin #16 of IC8, the next thing to check is if the anything is running and talking to anything at all. With a scope (...not an audio probe...) check for a square wave clock signal on either side of R78 (doesn't matter which). I'd be guessing at the frequency... "a couple of Mhz??"

[sirlemonhead]

Finally got the scope kit and have assembled it.

Provide I'm using it correctly, there's nothing on R78

Pin #16 of IC8 also has no signal on it.

Am I definitely out of luck at this stage?

[laurie]

Yeah... with the CPU not clocking anything it gets tricky from here. It *might* be a failed oscillator crystal or something, but we are entering the realm of needing "proper" test equipment...

I suspect the CPU was fried by reverse voltage or power surge or something. If so it is a Boss-specific part and not replaceable.