Acer Predator Helios 300 FH52M LA - J891P Rev 1b

[mcplslg123]

Re: Acer Predator Helios 300 FH52M LA - J891P Rev 1b

Are you sure EC_ON is measuring 5V? You can try de soldering DB2/3/4. Just desolder them and fix them on one pad so that you dont loose the parts. However,problem does not seems related to db2/3/4 to me but no harm in trying.Measur voltage on pin7/8/9/11/12 of PUM1 after triggering.

[tblazers]

Re: Acer Predator Helios 300 FH52M LA - J891P Rev 1b

oh yes correction EC_ON is 3.3V
Okay maybe i wont touch DB2/3/4 for now.


PUM1
ac only
pin7 14mV



on trigger
Pins
7 30mv
8 really quick jump to 1.5-2 V
9 13.4V
11 5.1V
12 5.1V

[mcplslg123]

Re: Acer Predator Helios 300 FH52M LA - J891P Rev 1b

Pin7 & 8 is enable and pin9 is Timer ON(TON). There should be resistor connected to pin9 of high value (400K-750K). Check its value as per schematics preferably out of circuit. This resistor should get 19V on one end and there should be 08-.09v approx on the other end of resistor(IC side). confirm your findings.

[tblazers]

Re: Acer Predator Helios 300 FH52M LA - J891P Rev 1b

Pin7 & 8 is enable and pin9 is Timer ON(TON). There should be resistor connected to pin9 of high value (400K-750K). Check its value as per schematics preferably out of circuit. This resistor should get 19V on one end and there should be 08-.09v approx on the other end of resistor(IC side). confirm your findings.

Thanks for your help

I am getting 13.4 V on the resistor PRM6 on Pin 2, Pin 1 is 19.6 V, this resistor does read 470K Ohm while on board.
seems odd if it is suppose to be 0.08V

[mcplslg123]

Re: Acer Predator Helios 300 FH52M LA - J891P Rev 1b

OK resistor PRM6 is not working as you have enables missing on pin7-8. What is resistance to GND on pin7 & 8 of PUM1? The resistance should be measured without any power source connected and better if you measure after 5 mins of disconnecting power so that circuit can discharge properly. To me, it seems like some shorting in SLP_S3/S5 probably.

[tblazers]

Re: Acer Predator Helios 300 FH52M LA - J891P Rev 1b

Thanks,

Interestingly I have

Pin 7 ~365K Ohm
Pin 8 ~1.1M Ohm


Where else could i check in SLP_S3 for a short.

[mcplslg123]

Re: Acer Predator Helios 300 FH52M LA - J891P Rev 1b

UQ1 & UQ2-voltage on pin 8-9 & 13-14 for the brief moment when it remains on? Resistance to GND on these pins for both load switch?

[tblazers]

Re: Acer Predator Helios 300 FH52M LA - J891P Rev 1b

UQ1
Pin 9/8 on trigger very quick 3.3V
Resistance to ground >2mohm
Pin 13/14 on trigger very quick 5V
Resistance to ground 7.5ohm

UQ1
Pin 8/9 on trigger 0v
resistance to ground 300Kohm
Pin 13/14 on trigger 0V
Resistance to ground 340ohm

[mcplslg123]

Re: Acer Predator Helios 300 FH52M LA - J891P Rev 1b

I beleive the lower measurements are for UQ2 and its typo. Going by your measurements for UQ1,pin13-14, you have a short to GND on +5VS line. Remove UQ1 and inject voltage on pin13-14 to findout what is short. You need a dc power supply to do that. Voltage injection should not be more then 1V.

[tblazers]

Re: Acer Predator Helios 300 FH52M LA - J891P Rev 1b

Yes correction bottom measurements are for UQ2,
Sounds i wassnt dure 7ohms would be considered a short, but I will inject 1V on the +5vs line.
Is it necessary to remove UQ1 when doing this ?

[mcplslg123]

Re: Acer Predator Helios 300 FH52M LA - J891P Rev 1b

Yes, you should remove UQ1 and then again measure resistance to gnd on pin13-14. If it still remains at 7 ohms,inject voltage to find out what is short. If the resistance climbs up significantly after removing UQ1,then this itself is faulty.

[Sephir0th]

Re: Acer Predator Helios 300 FH52M LA - J891P Rev 1b

This is actually a cool finding. If the +5VS stays at 7 Ohms after removal of UQ1 and if we consider +1.8VS being a issue too, then we immediately end up in the range of the Audio Codec, UA1 and I have to revise my theory of a defective PCH.

[tblazers]

Re: Acer Predator Helios 300 FH52M LA - J891P Rev 1b

Apologies for not listening to the jedi's fully
But i went on a slightly different route before i removed UQ1. I decided to desolder JPQ2 to isolate the 7 ohm, once +5Vs and +5Vs_out were decoupled the 7ohm disappeared on the UQ1 side, and the 7ohm remained on +5Vs line.
So injected on that line and found that the resistor near PUV1 is warming up (PRV42). But also PUV1 is warming up slightly too
Resistance across PRV42 is 3.4ohm while on board which i think is correct.
Could this resistor be the issue or would PUV1 be faulty?

Injected 1V on the +5Vs line and it is drawing 135mA.

Maybe we are close to the end of this saga haha

[Sephir0th]

Re: Acer Predator Helios 300 FH52M LA - J891P Rev 1b

Remove PRV42 to prove. Altwrnatively, in this case even the knowledge on which side of the 2.2Ohms resistor is the lower resistance to GND present should give the clue.

Either way, you're probably on the right track here.

[tblazers]

Re: Acer Predator Helios 300 FH52M LA - J891P Rev 1b

What's the point of a resistor like this it's like a fuse type wire with such low resistance?
Yes I will remove it tomorrow but
The resistance to gnd is lower on the puv1 side (5ohms),
So either PUV1 or the Cap on the same side, could the badcaps prophecy be fulfilled.. we'll find out tomorrow

[Sephir0th]

Re: Acer Predator Helios 300 FH52M LA - J891P Rev 1b

A Capacitor usually shorts out completely so probably not the case with 5 Ohms to GND. It is PUV1.

And yes, resistor purpose is likely to act like a very slow blow fuse. Actually it even didn't work in this case ( lol )

[mcplslg123]

Re: Acer Predator Helios 300 FH52M LA - J891P Rev 1b

Good to see you inching closer to fault.Remove PUV1 and check resistance to GND again on +5VS line. However, i'm afraid to say GPU may be dead as well.

[tblazers]

Re: Acer Predator Helios 300 FH52M LA - J891P Rev 1b

Good to see you inching closer to fault.Remove PUV1 and check resistance to GND again on +5VS line. However, i'm afraid to say GPU may be dead as well.

I haven't removed yet, but just wondering why would you expect the GPU to be dead, if i find that PUV1 is faulty how can i confirm GPU health before replacement of PUV1?

[Sephir0th]

Re: Acer Predator Helios 300 FH52M LA - J891P Rev 1b

You simply can't confirm right now. The usual task is to replace and see.

[tblazers]

Re: Acer Predator Helios 300 FH52M LA - J891P Rev 1b

Removed PUV1 and short on +5VS is gone, will have to order a UP9512QQKI
and see if it works