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820- 2532 not posting (not normal poly-tant problem)

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samiam

New member
820- 2532

slightl liquid residue on bottom of board between ports and fan, cleaned

powers on but no chime/post, randomly/intermittently every 8th time or so will turn on and work, but on restart not guaranteed to work again, once truly warmed up will usually be able to restart and be stable

replaced the poly-tants as Louis recommends (usually its C7771 causing the problem on this model):

C7771, C7660, C9560, C9510

now
P1V05S5_LL reading 1.2V should be 1.05V

any ideas on possible culprits?
 
larossmann

larossmann

Administrator
Staff member
Usually some corrosion on CPU vcore regulator U7100 on the edge of the board. Look close! Those little holes where something travels from one side of the board to another.
 
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samiam

New member
no definitely no spill that far over next to U7100, all of it was between fans and the ports, U3700 to U9500. i'm waiting for some 22uf to arrive to try a few more.

i replaced with standard cap where i could and unfortunately by new poly-tant on what i couldn't find/afford easily
 
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dukefawks

Administrator
You have liquid damaged board and are replacing caps....Logic would say something is corroded, this is not a cap problem.
When the machine does not boot, are all voltages present especially CPU Vcore?
 
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samiam

New member
so PPVCORE_S0_CPU is reading .99V instead of 1.25V
CPU is getting warm
which brings me to the U7100 circuit where I was already thinking of doing the poly tants C7117 and C7155

i've never worked on this circuit before, going to watch some more rossman vids, any other suggestions/ tips?
 
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dukefawks

Administrator
.99V on CPU is fine, it is a dynamic voltage set by CPU. This could be anything, corrosion somewhere under some chip. Only you saw where the corrosion was.....
 
S

samiam

New member
really not sure where to start, guess i'm going to have to go thru and measure every line and hope something shows up weird, powers on and fans run high but no post.

there was residue but almost no corrosion. only real corrosion was around some USB caps (C4605, L4605 and C9480 and C9481), I was getting 4.2V there, cleaned and now getting full 5V and 3.3V.
only other stuff that whatever liquid it was touched was the main ISL and C9590, realtek ethernet, and that whole firewire stuff next to it

any suggestions, i was assuming it had to be cpu, gpu or ram since it did post a few times, now i'm no longer getting any post no matter how many times i try
 
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