820-2850 green light but no power

[nate8organic]

Im pretty sure this board has a bad isl but i replaced it with one off a donor board but still got only a green light. double checked it was seated nice and it is. im getting 18.6v on pin 2 20ohm res on 27to28 and 3ohm 17to18. i am however getting a continuous voltage drop on pin 1 of the F7040 is there a short to ground there? the res to ground f7040 is .9 ohm on pin 2 and 9.+ ohms on pin 1.

I cant test it with another isl because i do not have anymore 2850 donor boards with the isl still intact. any way i can determine if it is or isnt the isl would really help.

Thanks in advance
Nate

 

[dukefawks]

What is resistance to GND on F7040? Of course on both sides must be the same or the fuse is dead.

 

[nate8organic]

i'm getting 5 ohms and dropping on the f7040, the fuse is good but when i measure voltage on the f7040 it starts at about 2v but drops all the way down to .3 and then the meter trips out and jumps up to 300volts and starts dropping.

 

[dukefawks]

Do you have a charged battery you can connect?

 

[nate8organic]

yeah, im pretty sure i got one with a good charge.

 

[dukefawks]

What voltage on PPBUS with a charged battery connected?

 

[nate8organic]

im getting 12.25 ppbus with battery connected

 

[dukefawks]

That means there is no short on PPBUS. So probably a dead ISL or bad soldering.

 

[nate8organic]

okay i will work on getting a new isl and test it. i tested it with 2 isl and double check the soldering so im pretty sure i dont have a good isl.

 

[dukefawks]

If the battery has a charge it should power on if you short the power pads now.