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Grubdac doesn't work. Please help. - Page 3

post #31 of 34
8/16/10 at 6:43am

You may have to.  There is no way to know for sure until you replace U2 and trying to power up and see what the chips do.  U3 has an absolute maximum voltage rating of 4.5V, so I'm not hopeful it has survived.  U1 has pins that are rated for only 4V, so same problem I suspect.

 

You can get all the replacement parts from Mouser - they are listed on the BOM:

http://diyforums.org/GrubDAC/GrubDAC-bom.php


Edited by cobaltmute - 8/16/10 at 6:45am
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post #32 of 34
8/16/10 at 8:02am
Thread Starter 

Oh gosh, I would have to pay 10€ of shipping for 3€ of chips!!!!

Do you think that now it is the only problecm? So if I replace the chips, the dac will work..

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post #33 of 34
8/16/10 at 10:28am

The problem is that we were looking for a short before you blew up the chip.  You reflowed, went to test and blew the regulator.    Now if we replace just the regulator, you may still have to original short or it may be a internal path inside a chip shorting to ground.

 

If you can get the parts off the board, clean the board (ie reflow just the pads and remove excess solder), check the board with a magnifier for any bridges or oddities, and then solder the new parts down, you should be good.

 

One other item to mention, as there has been one board with an issue, is that when you get the parts off, to check the top layer for any "odd" looking traces.  If you check the main grubDAC thread, you will see a case where there was some extra copper causing an issue.  You can also check this by testing the resistance from 3V3 to ground once the parts are removed.  It should be an ever increasing resistance as the bulk caps charge.

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post #34 of 34
8/16/10 at 12:27pm
Thread Starter 
Quote:
Originally Posted by cobaltmute View Post

The problem is that we were looking for a short before you blew up the chip.  You reflowed, went to test and blew the regulator.    Now if we replace just the regulator, you may still have to original short or it may be a internal path inside a chip shorting to ground.

 

If you can get the parts off the board, clean the board (ie reflow just the pads and remove excess solder), check the board with a magnifier for any bridges or oddities, and then solder the new parts down, you should be good.

 

One other item to mention, as there has been one board with an issue, is that when you get the parts off, to check the top layer for any "odd" looking traces.  If you check the main grubDAC thread, you will see a case where there was some extra copper causing an issue.  You can also check this by testing the resistance from 3V3 to ground once the parts are removed.  It should be an ever increasing resistance as the bulk caps charge.

I didn't know I could blew the chip just touching it with a pin of the tester!!!

However, this way I'll check if there are pcb problems as you have mentioned.

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