820-3115 Dead

Hi all,

I have an 820-3115 that is completely dead.

This is the history so far:

- No green light and 9 volts on pubs_g3h

- Replaced ISL6259 because it looked like it had a hole in it

- Green light restored

- Powered up normally.

I then plugged it back into the power supply and Q7085 started burning up then the whole thing died, so i replaced it and now i get nothing.

No green light, no voltage anywhere, on the power supply it just defaults to 2v and 1.14 amps.

I assume the PCH and SMC are okay as it did power on but now i have no idea.

I tried to inject voltage on the DC in fuse but again defaults to 2v and 1.14 amps.

PP3V42 Resistance to ground = 041.8 ohms
PPBUS_G3H Resistance to ground = 000.5 ohms --> i assume this is the problem but how can i check whats shorted if I can’t inject voltage?

Any ideas?
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ISL is dead again. Replace ISL Q7080/85 and Q7030/35. Also check R7005 and resistance between pins 17/18 27/28 on U7000.
Okay so replaced all of those and i have 16v coming in and green light - but drawing 0 amps and PPBUS_G3H is only 0.1v

Any idea what to do next? it seems ISL is not creating the 12v but it's been replaced twice now
Resistance to ground on PPBUS is 400k approx System side and 600k the other. ISL looks good and R7005 measures and looks okay too. Confused.com😩


Check if 16V is present on R7020. If it is present you probably have bad soldering somewhere or killed the ISL.