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the Power and Reset LEDs on my PC's...
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You are currently reading a thread in /diy/ - Do It yourself

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the Power and Reset LEDs on my PC's motherboard (like in pic) flicker when i turn on the PC - and the PC does not boot. if the speakers are plugged into the 3.5mm jack they pulse ("wow-wow-wow..." sound) at at the same frequency as the LEDs flicker (~20Hz).

i checked the voltages on all the connectors from the power supply and they're all good.

does anyone have any thoughts on what can cause this flickering? dead caps something? i suspect that the MB is fucked, but how can i figure out what failed?
>>
Trial and error, replace hardware until you pinpoint the damaged element.
Try a different psu for starters. Unplugging everything you don't need.
Sure it could be blown caps if your mobo is quite old. You'll know the bloated ones when you see them.
>>
>>934041

thx. forgot to mention that the MB is about 6 years old. all the caps look ok - no bulging or leaks. when i manually jump the "PS ON" and "GND" pins on the 24-pin PS connector, the PS turns on (and produces the correct voltages). but when i plug the 24-pin connector into the motherboard, the PS does not turn on. why is the motherboard not turning on the PS?
>>
>>934041
Again with /diy/ always always always starting the troubleshooting process with bad caps/solder joints/traces/etc. Why do you always start troubleshooting with the most invasive and convoluted shit?

OP, try replacing the battery on the motherboard first, then report back.
>>
>>934183
Either:

Your motherboard is fucked

or

Your standby-power is fucked

Test with a known-good power supply.
>>
>>933859
Most motherboards have a piezo on them that makes a sound. like a beep when you boot up your PC. One beep mean everything is OK. You can find this list using google. This will help you find the fault. If you don't get the beeb sounds that you have a bigger problem that might need some debugging gear.
>>
>>934186

the BIOS battery is ok, reads 3.14 V

no visible signs of damage on motherboard (leaks, burns, etc.)
>>
>>934241

no POST and no beep codes. just flickering LEDs (original pic) and flickering sound on 3.5mm audio jack.
>>
>>934242
Just because the battery reads OK with no load on it doesn't mean it's really ok. Replace it anyway.
>>
>>934256
Why are you assuming OP didn't measure it in-circuit?

Also why do you think it even matters? Literally all the battery does on ATX is power the clock when the computer is completely unplugged.
>>
>>934263

i removed the battery to measure it

without the battery the pc should still boot into original BIOS with an old date, right
>>
>>934269
Yep. The one and only thing the battery does (since ~1996) is keep the clock running when the PSU isn't supplying standby power.

That's why the batteries last so much longer now.
>>
>>934272
Alright, I told you how to fix it for $3. Go spend $50 on a power supply and see if that fixes it instead. Then go spend $150 on a new motherboard when you break the old one with your soldering iron. In fact, you can spend as much money fixing it as you want. I guess I just figured you might want to try the cheapest, lowest risk, most probable solution first.
>>
>>934186
In case you're temporarily fucking blind he started with the psu.
Also if you think caps are "convoluted" you should just stick to your ipad and fuck off this board.
>>
>>934292
Spoken like a man with virtually no real troubleshooting experience. Why don't you go back to repairing lifted traces and questionable solder joints?
>>
>>934293
Also, second most likely solution is that the ram is fried. Is the computer plugged in to a working surge protector? Any lightning storms recently?
>>
>>934293
>>934186
I'm not the guy you're shit talking, but caps are a valid suggestion in this case, not having a good battery is not going to cause pulsing like OP is seeing. My first thought would have been to take everything apart, clean, and re-seat components, then check psu voltages, then check by swapping psu for known good, then finally checking mobi/caps. Caps are generally the first thing to fail on a mobo (unless heat related) and what op describes sounds like bad caps to me. Source: a guy who fixes computers for a living.
>>
>>934503
>implying that aluminum caps are used for anything beyond power filtering

>implying that any cap actually used for signals isn't already tantalum

I definitely wouldn't want you working on my computer bro. Are you geek squad?
>>
OP do you have an esr meter? If not, invest in one and poke the shit out of those capacitors and find out which of them has gone bad.

Also - when stuff like this happens its mostly the caps on the CPU power supply side:
http://www.hardwaresecrets.com/everything-you-need-to-know-about-the-motherboard-voltage-regulator-circuit/1/
>>
>>934549
I guarantee you it's the PSU's +5VSB, and OP didn't bother to test this.
>>
>>934554
that feel when I like +5VSB

I took a power supply from a friend, and I am getting in to electronics so I am reading this Russian article about repairing +5VSB.

Imagine my happiness when I take the power supply, hear buzzing coming from the standby transformer, and see a rotten, blown up filtering capacitor. As soon as I put another one there, the +5VSB started working and everything was okay in the world. Only one capacitor made a difference between a working and a non-working power supply.
>>
>>935035
So you are OP and this problem is fixed?
>>
>>934513
Tantalum caps are fucking shitty, lazy cunts are desperate to fail at a moments notice
Ceramic is my favourite, classy and elegant. Poly film probably next because they are weird looking
>>
>>935088
No, he's lamenting on how he fixed a psu once and now that's the solution to everyone else's problems too
>>
op here

went out and bought a new psu. same fucking problem. the psu does not turned on when the 24-pin connector is plugged into the motherboard. if i jump the "psu on" pin on the psu side of the connector, the psu turns on.

am i doing something wrong? why won't the mb turn on the psu?
>>
>>935250
Is your power switch bad?
It has actually happened to me.

If not you have a motherboard problem.
>>
>>935250
If you are getting any light out of any led then the power supply is providing Atleast some power to the motherboard. It sounds like the motherboard is getting power, it's just not booting.

Did you try replacing the battery?

Next, did you try removing all the ram, then putting it back in, only one stick at a time, to see if your ram got zapped somehow? Or try removing the ram in there and putting in one known good stick of ram from a different computer?

There are only a couple of reasons that the computer won't boot if it's getting power.
>>
>>935250
Could be a short on the motherboard or some other device, the lights flickering is caused by the short circuit protection off the PSU kicking in.

Disconnect all non-essential items from the motherboard and PSU and run the board barebones.

If that doesn't work remove the motherboard and verify that nothing is shorting the board against the metal case from the underside. Long component leads sticking out can sometimes do this.
>>
>>933859

do you have a scope to probe a led
Thread replies: 29
Thread images: 1
Thread DB ID: 471522



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