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820-3115 PPBUS Short

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Ryanlen2

Member
Hey! I have this board that came in with no power. Short on PPBUS was .1 in diode. C7341 was getting very hot. I removed and now have .132 in diode on PPBUS. Same goes for S5_HS_Computing. PPDCIN is 16.8V.
Hoping the CPU is not dead, please advise on finding this short so that, I myself dont fuck it up being so close to CPU.

Thanks
 
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dukefawks

Administrator
PPBUS to GND resistance? Measure PPBUS to all coils to check for shorted high side FETs. PPBUS present at all?
 
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Ryanlen2

Member
PPBUS to GND from pin 1 of R4260 is .001 OHMs. PPBUS to coils L7550, L7510 and L7520 is .002 OHMs. PPBUS is 1.9V. Thanks Duke.

(PPBUS diode measurement from first post is incorrect. Sorry. )


******Scratch this entire post. I was in wrong mode. Be back with correct measurements. Ugh... Sorry.
 
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Ryanlen2

Member
OK, Here are correct measurement.

PPBUS to GND - 1.9 Ohms
PPBUS to L7550 - 2.7 Ohms
L7510 - 3.1 Ohms
L7520 - 3.1 Ohms
L7630 - 11.7 Ohms

PPBUS is 1.920 V

Thank you.
 
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Ryanlen2

Member
Hi! Injected power and found C7340 getting hot, though this was not the short I was looking for. Replaced C7340 and injected power again. This time the board is not drawing current. Voltage set to 3.5-5V and Amps stuck at 0. Only left it on for a couple mins. Any thoughts? Thanks, have a good one.
 
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dukefawks

Administrator
If C7340 got hot when injecting voltage on PPBUS then the DDR rail already saw 12V so the CPU is probably fried.
 
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Ryanlen2

Member
Ok Duke. Anything else I can do to confirm? Thank you. Btw, PPBUS does read the 3.5v being injected on multimeter. Not sure if this matters.
 
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