820-3115 - Green / Orange lights goes out after about 5 minutes.

[gcain]

Initially I get a green and orange light, which goes out after about five minutes of charging.

Once the light is out, the board seems to have a short on PPBus which is around 2v. If I inject power on PPBus the short goes away and I get a green light again.

It runs fine until I try charging it and start the above loop.

 

[larossmann]

I hate promoting this $900 POS but any chance you have a thermal camera you can use to record this process?

 

[dukefawks]

A short on PPBUS will not affect the green light normally. More likely 3V42 drops out or SMC stops working.

 

[gcain]

Louis, is there something about the thermal camera you need to share with us? You keep mentioning it to me.


PP3v42_G3H reads 0.003 in diode mode.
Put power on that rail, the draw starts high and goes straight down 0.04a... Again, the short is gone and the board works.

 

[dukefawks]

Probably the usual shorted cap under the foam pad next to the BIL connector.

 

[gcain]

I did check that cap already, but measuring again showed big voltage drop to ground. Obviously didn't check it properly.

I removed it and it's been happily charging a battery for 15 minutes.

Might have solved it.

 

[gcain]

What's the purpose of a cap that is between two power rails?

Does it work to balance the voltage on both sides?

 

[gcain]

Light stays on now, but the board turn on every time I connect power when the battery was left connected.

Runs off batter fine.

 

[RedDemonic]

copied from my thread:

Did you shut it down from within OSX?

 

[gcain]

The charging works okay on this one now but it kernel panics when left on for awhile and feels really hot, but the fans aren't spinning high.

Any suggestions?

External boot has the same result.

 

[dukefawks]

Bad RAM slot most common on these. Use only the one closest to the bottom, so the 2nd stick you normally plug in. But this thing was probably a liquid spill so it could also be corrosion somewhere.