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[SOLVED]820-3115, Single Beep after repairs

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SMMRepair

Member
Worked about 2 hours on an 820-3115 that had liquid to the area directly between the SMC and LVDS, about .5" in from the edge. Replaced quite a number of things, ran 4-5 wires, etc., but everything looked good and I had confidence it would work. Liquid didn't make it to the SMC from what I can tell, and the reverse side of the board is clean as a whistle.

Restored power and fan, but board beeps 1 time, which I know indicates a hardware failure on the board. How would I go about finding the fault that's causing the beep? Never really had a case like this one. I don't believe it's RAM related, but I'm not sure if the one-beep code can include circuitry for the RAM, or if that would "always" be a 3-beep pattern.

Any ideas?
 
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dukefawks

Administrator
Check the PCH SMBUS on diode mode R5200/01. If one of the chips on that bus is fucked it will not recognize RAM. Backlight chip is a main suspect.
 
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SMMRepair

Member
Thanks, duke. Sure enough there's a short on pin 2 of R5200. I did have to replace the LED driver, but replaced with a new one. That area in general looks kind of like garbage, but I cleaned it up well. I'll check it over again.
 
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SMMRepair

Member
Ok I think this one has a fucked CPU. It literally just singed the fuck out of me. I didn't notice it before because I had a sink on it to test. Damn. Sorry about that Duke, you can close this one.
 
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dukefawks

Administrator
Unlikely, the CPU needs to work in order to produce a beep. Pull R9753/9757 and see if the short on SMBUS is gone.
 
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SMMRepair

Member
Hey Duke, I removed R9753/9757 and the short has gone, yes. Does this mean LP8550 is in fact the culprit? Or just that there's a short on one of the pins of LP8550?
 
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SMMRepair

Member
Damn, you guys are champs. I've replaced hundreds of LP8550s, but either goofed this one up or had a bad chip (I probably fucked up, can't blame the chips every time--chip came from a roll of 100 and all others were fine). In any event, this ugly ass board actually works now--thanks, you guys. Always nice to have a board come to life after 2-3 hours of work. I hope the CPU is OK--it literally singed me to the point of leaving a blister.

Duke, you can close this one up as solved. Board chimes and is breathing.
 
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