820-02918 PPBUS Cycling, Minor Liquid.
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Update on this one: I actually noticed we had used an incompatible ISL (9900); I replaced with the correct one (9901) and the symptoms changed slightly; now PPBUS_AON cycles from ~11v to 12v, over and over. Not sure if this matters with regards to diagnosing this specific issue, but wanted to include it. -
820-02918 PPBUS Cycling, Minor Liquid.
Working on an 820-02918 board that had a minor liquid spill, but it was directly to the ISL/U5200. Essentially the entire area had to be replaced due to corrosion. Got it all cleaned up and everything looks good and checks out, but we're hitting a cycling PPBUS issue now. PPBUS_AON cycles quickly from ~9v-12v, indefinitely.
Knowing this is typically a sign of a possible short on a lower rail, we checked all around and found no obvious damage or shorts. We have VERY LIMITED parts for this model (exactly 1 single U5200 chip), but I suspect it will end up being a continuity issue or another component damaged by proxy during the original spill event.
Since this is the very first 820-02918 board we've seen and worked on, I figured I'd go ahead and ask the experts! Without a solid PPBUS, I figured we need to start there and get it stable first. Any and all help is very much appreciated!!Tags: None
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