Hello fellow DIYers,
A friend dropped off a DIY DAC based on stuffed PCB he purchased off of eBay, see attached picture. Unfortunately the DAC has developed a defect, one channel (left) drops out and distorts quite badly, which is why he asked me to repair it.
I looked it over, checked voltages etc. swapped out the opamps just to be sure, but the defect persists.
Currently I’m looking for a schematic, as without that it will take me hours to draw it up from the PCB. So if anyone has more info I’d appreciate hearing from you, thanks!
A friend dropped off a DIY DAC based on stuffed PCB he purchased off of eBay, see attached picture. Unfortunately the DAC has developed a defect, one channel (left) drops out and distorts quite badly, which is why he asked me to repair it.
I looked it over, checked voltages etc. swapped out the opamps just to be sure, but the defect persists.
Currently I’m looking for a schematic, as without that it will take me hours to draw it up from the PCB. So if anyone has more info I’d appreciate hearing from you, thanks!
Attachments
Its likely to be a faulty dac chip, i had a similar problem with parallel tda1543 dac. Only way to know is remove a dac and hope its the faulty one, if its not remove the other one and replace them both.
Thanks, I'm leaning in that direction too, but this would be a lot easier with a schematic though, as I hate going the trail and error route.
I'm intrigued by the array of 12 SOIC14 chips on the left hand side - is it a FIFO array or some such?
The rest of the circuit is easy to follow from the layout surely? 4 DACs and filters in the main section, 2 DACs or ADCs on the TOSLINK-S/PDIF section bottom left. You don't need a schematic, just the pinouts for the important chips so you can follow the signal path.
The rest of the circuit is easy to follow from the layout surely? 4 DACs and filters in the main section, 2 DACs or ADCs on the TOSLINK-S/PDIF section bottom left. You don't need a schematic, just the pinouts for the important chips so you can follow the signal path.
Of course, if you have plenty of spare time and don't mind spending hours on tracing out a PCB! 😀
My guess is 8 of them are two 32bit delays (probably shift regs like HC164) to re-purpose the I2S so as to feed left- and left+ to one pair of DACs and right-, right+ to the other.
Yes, that appears to be the case indeed, please have a look at the attached photo.
