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820-4924-A Power troubleshooting (Good Karma Fire damage fix)

brooke.j

brooke.j

Member
R1300 PIN 1. 3.34 PIN 2 = 3.33
R1301 PIN 1 = 3.34 PIN 2 = 2.98 (it moves from that to 3.03) is that considered pulsing or just my shaky hands?
R1302 PIN 1 = 3.33 PIN2 = 3.23
R1303 PIN1 = 3.34 PIN 2 = 3.33
 
brooke.j

brooke.j

Member
F7140 I'm getting 12.53 for PPBUS_G3H. Not 12.4 as I posted earlier. Is that still too low. Seems like 12.6v is what I want but that seems pretty close. If it is the SMC do you think it's worth reflowing because it might just be some corrosion. I've seen what it take to replace an SMC and I don't think I want to do that. If 12.53 for PPBUS_G3H is good then it's back to PP5V_S3 and PP3V3_S3 not being created. So what component creates those?
 
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dukefawks

Administrator
12.53 is ok for PPBUS. RTC looks fine, so this must give a pulse on PP5V_S3 when power is applied, check carefully pulses will be very short and best seen on a scope.
 
brooke.j

brooke.j

Member
I don't have a scope but I can see the voltage move from 0V to .01V in a pulsing pattern. Sorry for not having a scope that's my next purchase.
 
brooke.j

brooke.j

Member
I see from another post where 5V_S3 rails are missing that U7200 was shorted to ground. Now I know that this board is not that board and who knows what's shorted but should I be looking for a certain rail that's shorted to ground? Thanks so much for your help Duke. I feel like this board is being a devote christian on the first date. It's really gonna take some time to score.
 
brooke.j

brooke.j

Member
Hey Duke thanks again for the help. My mom can't wait for me to fix something so that I'll move out of her garage. I'm turning 40 this week so........ anyways the whole damn board was hit with a firehose. No really it was from a fire. It didn't get hot and there was no black marks on it. The board looked like a bucket full of shit but after the crest cleaning it did show me the battery dead symbol and after that I couldn't get it to boot. I realize this might be a dead end but I'm really learning so much and you are the man! Also it worked just for a second arg! I'd really like to know what the pulse signifies. Is that a pulse to switch states or is it a short to ground pulse? My mom says she'll bake you extra special cookies. I just wish she'd put on a shirt.
 
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dukefawks

Administrator
If any power rails does not come high in the specified time the power up sequence will start over again. This also happens when the ROM cannot be read, clock signals are missing or pretty much any other reason. Pulsing power can therefore be anything.
Most likely areas of corrosion are around SPI ROM and clock chip or U1950. There is no easy diagnostic for this problem and even for me would not be an easy repair.
 
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