820-3115 Light stays on, won't post. Was working fine.

[bjf]

This computer was working fine and then started getting stuck at POST with the HD light staying on and no display. It's a liquid-damaged board with scattered spots of corrosion on the top side only. I had to do a lot to fix the ISL chip but that was about it besides PBUS vsense. I've never seen this one before. I've gone over everything I can possible find. I replaced all of the components that looked remotely damaged. Any ideas on what might cause this or where I could go next?

 

[dukefawks]

CPU Vcore present? ALL_SYS_PWRGD present?

 

[bjf]

Yes, of course, sorry, I forgot to mention the obvious things. They're both good. CPU Vcore is at 1.1V without RAM and goes to 0.9V with RAM. ALL_SYS_PWRGD is at 3.3V. That's where I always go with no display, CPU Vcore, but this one is different. It's on the verge of posting, the optical drive makes its startup noise and then the light just gets stuck.

 

[dukefawks]

Corrosion under PCH or SMC likely. Some flux and 150C heat, do NOT reflow.

 

[bjf]

Yeah, I tried that one. I'll give it another go as it's tricky to really feel like that process is very thorough as you're doing it. Thanks for the input, I'll post once I see where this goes.

 

[bjf]

No luck. I was pretty thorough with it. Kept it at 150C. I'm out of ideas at this point.

 

[Sykulski]

Could it be BIOS related maybe ??

 

[larossmann]

99% chance something under the PCH. duke will hurt me if i tell you to reflow it to fix it... so i won't say that.

 

[bjf]

Ok, I'll go with that. There was absolutely no sign of liquid-damage or liquid on the bottom of the board, only on top, as seen in the pictures I put up, but I'll give it a shot. Thanks for the tip, I'll update.