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Hi,
I'm trying to repair a PCM41 that has no delay signal at all when the mix control is turned fully wet.
I've been probing the circuit and comparing measurements with the help of Claude, but at this point it feels like I'm going in circles. Fortunately, I have a second, fully working PCM41 that I've been using as a reference to compare signals and voltages throughout the circuit.
To rule out faulty ICs, I've swapped every socketed chip from the non-working unit into the working unit. The working unit continued to function normally with every chip installed, which strongly suggests the ICs themselves are not the source of the problem. I've also completely recapped the non-working unit.
I feel like I made some headway with the unit, and determined that it seems that the sample and hold function u23, theres no input or output from it, so im thinking its this part thats not working correctly somethings I found. Mostly in the C4/D4 section of schematic 4
Also here's the schematic. I have a scope, and multimeter, but don't have the signature analyzer as well!
Thanks Any help would be appreciated !!!
https://audiocircuit.dk/downloads/lexicon/Lexicon-PCM41-ddp-sm.pdf
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I'm trying to repair a PCM41 that has no delay signal at all when the mix control is turned fully wet.
I've been probing the circuit and comparing measurements with the help of Claude, but at this point it feels like I'm going in circles. Fortunately, I have a second, fully working PCM41 that I've been using as a reference to compare signals and voltages throughout the circuit.
To rule out faulty ICs, I've swapped every socketed chip from the non-working unit into the working unit. The working unit continued to function normally with every chip installed, which strongly suggests the ICs themselves are not the source of the problem. I've also completely recapped the non-working unit.
I feel like I made some headway with the unit, and determined that it seems that the sample and hold function u23, theres no input or output from it, so im thinking its this part thats not working correctly somethings I found. Mostly in the C4/D4 section of schematic 4
- R102 connected to q4 is severely under voltage compared to the good unit
- 95, show 15 volts on both sides, instead of just one side. The good one shows 3volts
- I get signal on pin 6 of u22 but none of the others on that IC, I know these work in tandem so I'm not sure if thats nice clue or not?
Also here's the schematic. I have a scope, and multimeter, but don't have the signature analyzer as well!
Thanks Any help would be appreciated !!!
https://audiocircuit.dk/downloads/lexicon/Lexicon-PCM41-ddp-sm.pdf
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