[Acer 6930G] Lower +5V problem.

[nomorebeer]

Hello guys. First, English is not my primary language sorry about that.

Issue: When i run my computer, after a while like 30 mins or 1 hour (i guess depends system load) i get some very complicated symptoms. Well i just test voltages; after 5 minutes i run my computer, 5V goes lower like, 4.95 ... 10 mins later 4.89... and 30 mins later its goes too low like 4.40 etc and finaly it drops like 4.10 and symptoms came around. Well i just downloaded dataSheet, you can find here;



I check the page 33 (about voltage place) ... I saw there is 5V output from PQ14 (FDS8884). So i checked voltages on PQ14, input pins of 5.07 volt is always good there( wich is input of PQ14 (+5VPCU) , (so i guess thats means ISL6237 regulator is working fine...) But the output pin of PQ14 wich is +5V goes out there is not good... starting going down couple mins later of my computer run... So i just tried to replace two parts: PQ14 and there is little capacitor at the PQ14 ( PC63 -1u/25V). But problem is still same. Is there anyone help me about to find out, why this 5v goes down every minute like 3% or someting? Thank you!

[nomorebeer]

Re: [Acer 6930G] Lower +5V problem.

No ideas? :\

[ben7]

Re: [Acer 6930G] Lower +5V problem.

My guess is that a capacitor might have broken, causing the regulator to be unstable, and decrease output voltage over time. Something might be getting too hot, and temperature limiting could be kicking in.

Oh yeah, check the voltage on MAIND over time, see if it decreases too.

[nomorebeer]

Re: [Acer 6930G] Lower +5V problem.

My guess is that a capacitor might have broken, causing the regulator to be unstable, and decrease output voltage over time. Something might be getting too hot, and temperature limiting could be kicking in.

Oh yeah, check the voltage on MAIND over time, see if it decreases too.

Thank you for answer. I checked MAIND right know, but when i touch that pin wich is PQ14's pin 4, computer resets itself, i can not check it. Why is that?

P.S: I also adding picture about about MAIND where made ( i'm not sure that is the right place on datasheet?) (page 38)

[ben7]

Re: [Acer 6930G] Lower +5V problem.

Thank you for answer. I checked MAIND right know, but when i touch that pin wich is PQ14's pin 4, computer resets itself, i can not check it. Why is that?

P.S: I also adding picture about about MAIND where made ( i'm not sure that is the right place on datasheet?) (page 38)

Hm, you are discharging the gate of the MOSFET when you touch it. Over time the 5v is dropping because the gate is slowly discharging!

[nomorebeer]

Re: [Acer 6930G] Lower +5V problem.

So what is the problem, do you have any idea? I'm pretty new on electronics, kind a hobby you know. But this discharging problem occours when i trying to check it, or there is already a problem cause this?

[ben7]

Re: [Acer 6930G] Lower +5V problem.

How is the +15v rail?

[nomorebeer]

Re: [Acer 6930G] Lower +5V problem.

Let me fast check..

[nomorebeer]

Re: [Acer 6930G] Lower +5V problem.

15V rail looks; 13.5V .. is that too bad? And do i need to wait a while is that decreasing or some?

[ben7]

Re: [Acer 6930G] Lower +5V problem.

15V rail looks; 13.5V .. is that too bad? And do i need to wait a while is that decreasing or some?

That might be the problem. 15v rail is definitely out of tolerance. Yes see if it decreases too over time. Where does the 15v come from?

[nomorebeer]

Re: [Acer 6930G] Lower +5V problem.

I wait a while but 13.5 is stable, not changing.

[ben7]

Re: [Acer 6930G] Lower +5V problem.

What is the voltage on +15_ALWP?

[nomorebeer]

Re: [Acer 6930G] Lower +5V problem.

What is the voltage on +15_ALWP?

Same...

+15V : 13.55V
+15v_ALWP : 13.55V


Additional information: There is another FET named PQ16 for 5V_S5 out, it's using same +15V for gate. And output is stable. I mean PQ16 pin 123 is 5.07V not decreasing. By the way, i can not check the gate voltage on PQ16 (S5D) also it's causes reset. Any idea?

[ben7]

Re: [Acer 6930G] Lower +5V problem.

Where does the REFIN2 come from?

[nomorebeer]

Re: [Acer 6930G] Lower +5V problem.

Where does the REFIN2 come from?

It's important: I check the circuit, i double checked, i guess there is; PR76, PR77, PR78 is NOT placed on circuit. Those Resistors places are EMPTY. I guess this information could be usefull for you. by the way ben7 thank you so much your trying to help me i respect that. And if you don't mind i share datasheet on my first post, if you able to download and check it you can look wherever you want on circuit. Thank you so much, i hope we get someting on this issue.. Regards.

[ben7]

Re: [Acer 6930G] Lower +5V problem.

Hey, thank you for being patient with me too LOL. I'm blind when it comes to reading posts, I didn't realize you had a link for the pdf.

[ben7]

Re: [Acer 6930G] Lower +5V problem.

My guess right now is that any one of PD9, PD10, PC43, PC48, PC49, PC50 could be faulty.

[nomorebeer]

Re: [Acer 6930G] Lower +5V problem.

Well do you think lower +15 voltage cause this problem?

[ben7]

Re: [Acer 6930G] Lower +5V problem.

Well do you think lower +15 voltage cause this problem?

Yeah, did you check the parts I mentioned?

The 15v there comes from a voltage tripler circuit, and it might be the problem. I'm not sure if the 15v goes elsewhere, which it might. Then there could be a different problem - too much of a load on the 15v

[nomorebeer]

Re: [Acer 6930G] Lower +5V problem.

I was check PQ16 before and;

FET named PQ16 for 5V_S5 out, it's using same +15V for gate. And output is stable. I mean PQ16 pin 123 is 5.07V not decreasing.

So if the problem is 15V, also this PQ16 has to be any problems too?