Toshiba satellite m645 fluctuating voltage

[String2016]

I need help on this please , I have a problem with this toshiba satellite m645 NBQAA LA-6071P REV 1.0.The problem is fluctuating voltage of PQ8 voltages start from 16v then fluctuate to drop and same on current sense resistor PR45. attached is the schematic , can someone please help the problem of the laptop when pressing power button 1 second goes off

[SMDFlea]

Re: Toshiba satellite m645 fluctuating voltage

Any voltage measurements ? , have you checked all the mosfets ? .You should know by now that the more info you can give the more likely you are to receive help.

[String2016]

Re: Toshiba satellite m645 fluctuating voltage

Already check PQ7 Both sides have 19v but Pq8 S=19V but drain is fluctuating voltage only 16v then drop

[String2016]

Re: Toshiba satellite m645 fluctuating voltage

anyone could help on this please

[Techtiger]

Re: Toshiba satellite m645 fluctuating voltage

1st do a cool check up PQ7/8/6 S D G Diode mode is those Fets are ok what is voltage on be Gate of PQ7/8? Is the pin 4 of 2 fets +8V ?

[Techtiger]

Re: Toshiba satellite m645 fluctuating voltage

Remove PJ18 & check if the fluctuatingbis gone

[String2016]

Re: Toshiba satellite m645 fluctuating voltage

pq7 s=4.6k g=4.9k d=59.8 on pq8 s=4.6k g=4.9k d=21.8k on voltage pq7 s=19v g=19v d=19v pq8 s=19v g=19v d=16v fluctuating dropping voltage, i cannot find pj18 on the board i only found pj17

[Techtiger]

Re: Toshiba satellite m645 fluctuating voltage

May be PQ8 faulty test it on Diode mode , & the 1st 2fets are not switching find out PACIN Voltage?

PQ7/8 For P-Channel Fet
Red Pro to Drain Black Pro to Sorce no Value or High

Red Pro to Source Black Pro to Drain Value 50-500 ohms

Red Pro to Source Black Pro to Gate No Value or high

Red Pro to Drain Black Pro to Gate No Value or high

[String2016]

Re: Toshiba satellite m645 fluctuating voltage

thanks for the response, pq7 is good but pq8 Red Pro to Source Black Pro to Drain Value 50-500 ohms = no value, I already tried removing pq8 and check on drain side without it still fluctuating voltage

[String2016]

Re: Toshiba satellite m645 fluctuating voltage

removed pq7 and test still voltage is fluctuating on pq8

[String2016]

Re: Toshiba satellite m645 fluctuating voltage

tried removed both pq7 and pq8 still same fluctuating vltage

[String2016]

Re: Toshiba satellite m645 fluctuating voltage

anyone please help

[SMDFlea]

Re: Toshiba satellite m645 fluctuating voltage

check resistance on PQ6 s/g/d

[String2016]

Re: Toshiba satellite m645 fluctuating voltage

here it is
PQ6

Red Pro to Drain Black Pro to Sorce = 0.400

Red Pro to Source Black Pro to Drain = goes for 1.6 then fluctuate to no value

Red Pro to Source Black Pro to Gate=no value

Red Pro to Drain Black Pro to Gate= no value

[Techtiger]

Re: Toshiba satellite m645 fluctuating voltage

After removing PQ8 what is the voltage on the drain side ? Do y have the DC LAB?

[String2016]

Re: Toshiba satellite m645 fluctuating voltage

@techtiger removing pq8 voltage on the drain side same 16v fluctuating, i have bench lab and already tried injecting voltage nothings happens it taking only 0.125amps

[String2016]

Re: Toshiba satellite m645 fluctuating voltage

even pq6 both drain and source are fluctuating voltage

[Techtiger]

Re: Toshiba satellite m645 fluctuating voltage

Remove PR45 and feed back which site is fluctuationg ?

[String2016]

Re: Toshiba satellite m645 fluctuating voltage

removed pr45 both sides fluctuate

[String2016]

Re: Toshiba satellite m645 fluctuating voltage

anyone can help