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The GrubDAC
Oct 2, 2011 at 10:13 AM Post #767 of 1,079
Reflowed TPS chip, PCM chip, Wolfson chip, oscillator chip and L1 = can't get it going. The TPS chip usually gets hot upon connecting the DAC, I then shut it down. A couple of times now I've had it running withouth the TPS getting hot, my voltage at 5V is right at 4.86V, but the 3.3V is at 0.45V.

Pics:







Dirty board, I know, only have PRF 6-68 "dry" electronics cleaner that doesn't do that good of a job :wink:
 
Oct 2, 2011 at 10:52 AM Post #768 of 1,079
Check all your pins near pin 1 (the dot) on the PCM2707. Looks like you may have some bridge their.

Test the resistance between the 3v3 point and 0V - should be high - if not you're tracing bridges.
 
Oct 2, 2011 at 12:02 PM Post #769 of 1,079
cobaltmute said:
Check all your pins near pin 1 (the dot) on the PCM2707. Looks like you may have some bridge their.
Test the resistance between the 3v3 point and 0V - should be high - if not you're tracing bridges.
Click to expand...


Reflowed the pins close to pin 1 and measured about 18 ohms betveen 3.3V and 0V - still, on pluging in the DAC the TSP got hot again.
 
Oct 2, 2011 at 12:59 PM Post #770 of 1,079
I'd clean up C7.
The solder overlaps an adjacent trace and the solder mask does
not alway prevent a short.
 
Edit: Checked a bare board...they are supposed to overlap.
 
Oct 2, 2011 at 2:50 PM Post #771 of 1,079
avro_arrow said:
I'd clean up C7.
The solder overlaps an adjacent trace and the solder mask does
not alway prevent a short.
 
Edit: Checked a bare board...they are supposed to overlap.
Click to expand...


ARGH! Desoldered C7 to get to see the TPS chip connections better and *snap* said the tweezers and *boing* went the cap. :confused_face(1): where to get a new one here in Finland, buuh.
 
Oct 2, 2011 at 4:55 PM Post #773 of 1,079

I've had that happen too...
confused_face.gif

 
Quote:
lehtinel said:
ARGH! Desoldered C7 to get to see the TPS chip connections better and *snap* said the tweezers and *boing* went the cap.
confused_face(1).gif
where to get a new one here in Finland, buuh.
Click to expand...



 
 
Oct 4, 2011 at 5:37 AM Post #774 of 1,079
Placed an order today on the exact same capaciotor as shipped with the DAC, 10pcs. so I will not be as disturbed if I loose a few :wink: Two TPS chips also coming up. Shameful thing about the order was ofcourse that the shipping vas 70% of the price, got away cheap anyways so, no big deal.
 
I really hope this will sort out my GrubDAC.
 
Oct 15, 2011 at 11:54 AM Post #775 of 1,079
Got the spare parts, soldered the C7 in, cleaned up the pins on the TPS-chip, plugged it in, 0.13V at 3.3V point. Shut it down and check for bridges, what I see is a nasty bridge over from the last pin on the TPS-chip to the C7. Can't get the solder out, it's pinned to the surface of the PCB and formed a clean trace along the PCB tracing.
 
ARGH! So annoying I set the whole thing aside.
 
Nov 6, 2011 at 3:18 PM Post #776 of 1,079
Tinkered with the DAC today. No progress though. A new TPS chip in place i checked for solder joints on the chips, got a 0 - 3.3V resistance of some 70ohms. When I plugged the DAC in the port the Wolfson chip gave out some smoke - bad news I guess.
 
Will se if I'll place a new order on a second kit and do one from scratch.
 
Nov 6, 2011 at 7:45 PM Post #777 of 1,079


Quote:
lehtinel said:
Tinkered with the DAC today. No progress though. A new TPS chip in place i checked for solder joints on the chips, got a 0 - 3.3V resistance of some 70ohms. When I plugged the DAC in the port the Wolfson chip gave out some smoke - bad news I guess.
 
Will se if I'll place a new order on a second kit and do one from scratch.
Click to expand...

I'm sorry you're having such bad luck with it.
frown.gif


 
 
 
Nov 10, 2011 at 11:19 AM Post #779 of 1,079
Well. I've got a problem :) 
 
I assembled the board. Took a bit of time, but it went great. I powered it up, LED is on, no detection. 
 
After some quick debugging, here's the status. Regulator gets hot, therefore there's a short somewhere. TP1 to ground is 0 ohm. Bad. 
 
Reflowed the usual suspects. Even though they did look quite shiny already. No chance. I resoldered a few caps that I suspected as well, but no luck. 
 
I'd love a second pair of eyes to help me out. Here are some macro shots:
 
https://picasaweb.google.com/theatilla/BrokenGrubDac?authuser=0&feat=directlink
 
It's something on the left side of the r6, r4, r1 arc, since on the right side there's a bit of resistance. 
 
Nov 10, 2011 at 7:32 PM Post #780 of 1,079


Quote:
atilla said:
Well. I've got a problem :) 
 
I assembled the board. Took a bit of time, but it went great. I powered it up, LED is on, no detection. 
 
After some quick debugging, here's the status. Regulator gets hot, therefore there's a short somewhere. TP1 to ground is 0 ohm. Bad. 
 
Reflowed the usual suspects. Even though they did look quite shiny already. No chance. I resoldered a few caps that I suspected as well, but no luck. 
 
I'd love a second pair of eyes to help me out. Here are some macro shots:
 
https://picasaweb.google.com/theatilla/BrokenGrubDac?authuser=0&feat=directlink
 
It's something on the left side of the r6, r4, r1 arc, since on the right side there's a bit of resistance. 
Click to expand...


Sorry you're having trouble, but can you check that link to your pics?  All I get is a "Page Not Found" error.
 
 
 
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