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820-2914-b dim green light wont turn on

Gmorb

Gmorb

Member
Board gets 16.5 volts and dim green light while using adaptor but i noticed certain points like pp3v42 and so on show 16.5 volts as if voltage is not being regulated. I connected the board using a benchtop power supply to force 18.5 volts and although i get the voltage set, amps are very low 0.0057 and still no voltage regulation. Ive replaced components which were not giving me a proper resistance or ohm readout on the 1 wire circuit but no luck.
 
Gurmon

Gurmon

Member
if you got really 16.5v on PP3v42_G3H, This board is toast

Lets start with powerrails

PPBUS_G3H =
PP3v42 =
PP5v_S5 =

Then we can help you narrow the fault down.
 
D

dukefawks

Administrator
So there is no 3V42.
Are you measuring resistance to GND on PPBUS with power applied? I hope not...
Resistance to GND on PP3V42?
 
Gmorb

Gmorb

Member
Ok, resistance to ground on ppbus_g3h starts at 6.00 and keeps rising im assuming thats good.resistance to ground on pp3v42 is 33.0 and rises. I did further investigating and found that when i provided the board with 18.5 volts everything around the u6990 voltage regulator chip was shorting to ground. When i raise the voltage even further the chip would get extremely hot. Is it normal for everything to short around that chip? I went ahead and removed it and short dissapeared on all components around it. Bad chip?
 
D

dukefawks

Administrator
What what? 6.00 Ohms, kOhms, mOhms? You are intentionally giving the board more than 18.5V? This is all a good way to kill a board.
I still need to know resistance to GND on PPBUS and PP3V42. A short on 3V42 will also cause U6990 to heat up.
 
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