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dead Acer aspire 5738Z
https://vlab.su/viewtopic.php?f=59&t=32105		 Страница 1 из 1
mohkam3000 [ 05 май 2015, 01:07 ]
Заголовок сообщения:  dead Acer aspire 5738Z
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 ?
andromedax [ 05 май 2015, 21:27 ]
Заголовок сообщения:  Re: dead Acer aspire 5738Z
Цитата:
VDD and VDDP = +3.3V ok


It should be 5V_S5 (5v.)

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

Цитата:
TON is +0.9V must be +19V I think. C696 and R418 are checked ok.

TON, goes to +19V trough R418, so voltage +0.9V is good.
mohkam3000 [ 06 май 2015, 00:16 ]
Заголовок сообщения:  Re: dead Acer aspire 5738Z
andromedax писал(а):
Цитата:
VDD and VDDP = +3.3V ok


It should be 5V_S5 (5v.)[/b]

Y're right, I made mistake when writing figures. They measured rather 5V_S5.

Цитата:
TON is +0.9V must be +19V I think. C696 and R418 are checked ok.

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 ?
andromedax [ 06 май 2015, 09:47 ]
Заголовок сообщения:  Re: dead Acer aspire 5738Z
Цитата:

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.
mohkam3000 [ 06 май 2015, 16:59 ]
Заголовок сообщения:  Re: dead Acer aspire 5738Z
[/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?
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