Fully balanced TDA1305 - eBay

[SSassen]

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!

 

[Luke]

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.

 

[SSassen]

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.

 

[Mark Tillotson]

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.

 

[SSassen]

The rest of the circuit is easy to follow from the layout surely?

Of course, if you have plenty of spare time and don't mind spending hours on tracing out a PCB!

 

[abraxalito]

I'm intrigued by the array of 12 SOIC14 chips on the left hand side - is it a FIFO array or some such?

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.

 

[SSassen]

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.