LA-A091P power issue

[rookieme]

Hi team,
at this board I'm having no power issue.
I have 19V at the output of PQ301 but 0V at output of PQ302.
I'm not sure what to check.
Both of them share the same gate (19V) and are in working condition.

[angel-boy]

Re: LA-A091P power issue

check pq304 and 303, you dont receive the gate for pq301 and 302 ( 4pin)

Is posible to have a short after 301, and that`s why power missing.

You chan short pq301, and measure pq302 out , if is 0v, short before pq301 and after pq302

[rookieme]

Re: LA-A091P power issue

I have already checked pq303 & pq304 and they have no short.
In fact I have removed pq304 and had the same result.
I see no short, current flows from pq301 but not from pq302.
What voltage should pq302 have at the gate in order to let the current flow?

[meritosari]

Re: LA-A091P power issue

What voltage should pq302 have at the gate in order to let the current flow?

+ 7-9v

[rookieme]

Re: LA-A091P power issue

I get 19V there...

[meritosari]

Re: LA-A091P power issue

-voltage acdet and acok?
-voltage PQ303 PQ304 PQ307?

[samanthban]

Re: LA-A091P power issue

you need negative voltage to open the fet check pq 307 pin 5

[rookieme]

Re: LA-A091P power issue

ACOK 4,3V
ACDET 3,2V
PQ307 pin6 13,1 V pin2 ~0V
PQ303 pin2 13,1 V pin1 17,5V
PQ304 pin2 17,5 V pin1 19,7 V pin3 19,7V

[rookieme]

Re: LA-A091P power issue

you need negative voltage to open the fet check pq 307 pin 5

PQ307 pin5 ~0V, pin3 16V

[samanthban]

Re: LA-A091P power issue

PQ307 pin5 ~0V, pin3 16V

Ok.. check pq 308 voltage

[rookieme]

Re: LA-A091P power issue

PQ308 pin2 4,2 V pin1 ~0V

[samanthban]

Re: LA-A091P power issue

PQ308 pin2 4,2 V pin1 ~0V

I think this is the culprit check this transistor.

[fddizon]

Re: LA-A091P power issue

check PQ302 pin 5678 against ground

(this will Bypass protection circuit)
if there is no short, lift pin 4 of FET PQ302. signal will pass.
if DC bench is available use it as the source

if no dc bench
Note: make a quick insert of the adapter and check parts that will heat up. quickly remove if smoke will come up
with this method, you will quickly find the shorted component.

[rookieme]

Re: LA-A091P power issue

check PQ302 pin 5678 against ground

(this will Bypass protection circuit)
if there is no short, lift pin 4 of FET PQ302. signal will pass.
if DC bench is available use it as the source

if no dc bench
Note: make a quick insert of the adapter and check parts that will heat up. quickly remove if smoke will come up
with this method, you will quickly find the shorted component.

That is correct, I have a short after the PQ302.
Previously I have done a reballing at GPU and I think that a component didn't survive the heat, it's not the GPU [I removed it again].
I'll make some measures before connecting power.

[rookieme]

Re: LA-A091P power issue

Finaly it was a bad cap, I used a AA power cell 1,5V that managed to make the cap boiling hot.
Thank you all for your time.

[angel-boy]

Re: LA-A091P power issue

i told you this from begining ))


i did not tell you to check for short, i told you to make a short ( create ) you must unit the pq301 ( 8.7.6.5 pins ) with ( pq302 8.7.6.5 pins )

[rookieme]

Re: LA-A091P power issue

Sometimes I'm a bit rookie

[angel-boy]

Re: LA-A091P power issue

is important that mainboard work now.

[samanthban]

Re: LA-A091P power issue

check PQ302 pin 5678 against ground

(this will Bypass protection circuit)
if there is no short, lift pin 4 of FET PQ302. signal will pass.
if DC bench is available use it as the source

if no dc bench
Note: make a quick insert of the adapter and check parts that will heat up. quickly remove if smoke will come up
with this method, you will quickly find the shorted component.

very nice thanks for sharing

[abbas_govani]

Re: LA-A091P power issue

Hi guys,
i have a problem with this board,
pu401 is getting heated. i checked there is 8 ohms on pc414 witch is +3vlp.
i removed thi ic and capacitor too but the resistance is same. can any one have any idea to rectify this problem.

thanks in advance.