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pupDAC Step-by-Step Build Thread - Page 22

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Edited by nivz - Yesterday at 11:28 pm
post #317 of 317
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Originally Posted by nivz View Post
 

Thanks for the advice TomB.. I cleaned the board with flux cleaner and deionised water, let it dry under a bulb for about 12hrs.. the problem is still there.. On the PCM1794, There's a bridge on pins 11 and 12, I've scratched the soldermask on the via next to these pads so it's impossible to remove that bridge now, on the schematic these two pins are grounded (FMT0 and FMT1), So I left the bridge as it is.. I didn't think this could be the problem as those two pins are connected to the same via (one I managed to scrape the soldermask off) that goes to C8 on the other side anyway...

 

I'm very new at this so I don't know how I should go about checking if a cap is shorting, can I just check the voltage across every cap? I'll try to post some photos if I can get something to focus close enough to see the details of the board.. Thanks again!

 

Edit:

 

Pics:

1794

[IMG]http://i57.tinypic.com/so4tqh.jpg[/IMG]

 

2707

[IMG]http://i62.tinypic.com/2vw8ep5.jpg[/IMG]

 

Board top

[IMG]http://i62.tinypic.com/qnpqmt.jpg[/IMG]

 

Board bottom

[IMG]http://i59.tinypic.com/kq2qs.jpg[/IMG]


To tell the truth, I don't see any issue with the PCM chips.  Another thing that can cause the symptoms you describe is the opamp.  Are you certain everything is clean and dry around it?  The fact that you haven't trimmed any leads is suspect.  Conceivably, those could be touching something and arcing when you're trying to operate the DAC.  Also look for anything that might be shorting right around the opamp.  It looks like you used the OPA2835.  The 2836 is much, much better.

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