hi
Got dead Acer Aspire 5738Z for Repair.
Platform: JV50-MV M92MB (discrete)
Found shorted VGA_CORE_PWR output, changed U41 fet and short was gone now laptop powers up with no display and VGA_CORE_PWR =+0V Changed U45 RT8202A then U40, always same.

Main working voltage measured for RT8202A :
VDD and VDDP = +3.3V ok
EN_VGA = +3.3V ok

But :
TON is +0.9V must be +19V I think. C696 and R418 are checked ok.
RT8202_DH_VGA=+0V, it should be high ??
and RT8202_DL_VGA=+3.3Vit should be low??

P.S help with idea as what to check next to get VGA_CORE_PWR output ?

It should be 5V_S5 (5v.)

Have you checked R426?, I think it is open.


TON, goes to +19V trough R418, so voltage +0.9V is good.

I was thinking that +19V going through R418 should be rather high and not so low.

Do you confirm that +0.9V could be ok ?

TON input is connected to DCBATOUT_8202_VGA (19v.) through a 1 Mohm. resistor, and it is an input comparator to set switching frequency.

I think +0.9V could be a good voltage for an input comparator.

[/quote]TON input is connected to DCBATOUT_8202_VGA (19v.) through a 1 Mohm. resistor, and it is an input comparator to set switching frequency.

I think +0.9V could be a good voltage for an input comparator.[/quote]

Ok I admit it.

Do you have any idea as what to check next to Get VGA_CORE_PWR output?