Biostar U8668 Grand power issues

[DankEngihn]

I have a Socket 478 Biostar motherboard that has some issues.

It powers up for a second or two, and shuts off. To get it to power back on, I have to unplug the power supply from the wall, and plug it back in. This alone isn't too strange of a problem, but there's something else too. I plugged in an AGP graphics card to see if it made an difference, and with the AGP card in, the CPU fan runs slower for the few seconds that it actually stays on. I know it's not the power supply, because it works fine with another board. It's not the RAM, because the computer I took it out of POSTed perfectly fine with it in. I'm pretty sure the CPU works, but by now I'm out of Ideas. All of the caps look good, and when I got it, I did a thorough cleaning of the board, which didn't help anything at all. I really like this board, so I don't want to throw it out. Nothing is burned, or broken. None of the chip legs are touching. Any ideas on what could be wrong?

The power supply that was previously running the board, the fan seized, and it overheated. I'm beginning to suspect that when the crappy power supply overheated, it dead-shorted some of the capacitors on the motherboard. Would a recap help?

[Sparkey55]

Re: Biostar U8668 Grand power issues

I have a Socket 478 Biostar motherboard that has some issues.

It powers up for a second or two, and shuts off. To get it to power back on, I have to unplug the power supply from the wall, and plug it back in. This alone isn't too strange of a problem, but there's something else too. I plugged in an AGP graphics card to see if it made an difference, and with the AGP card in, the CPU fan runs slower for the few seconds that it actually stays on. I know it's not the power supply, because it works fine with another board. It's not the RAM, because the computer I took it out of POSTed perfectly fine with it in. I'm pretty sure the CPU works, but by now I'm out of Ideas. All of the caps look good, and when I got it, I did a thorough cleaning of the board, which didn't help anything at all. I really like this board, so I don't want to throw it out. Nothing is burned, or broken. None of the chip legs are touching. Any ideas on what could be wrong?

The power supply that was previously running the board, the fan seized, and it overheated. I'm beginning to suspect that when the crappy power supply overheated, it dead-shorted some of the capacitors on the motherboard. Would a recap help?

We need more info and photos. What PSU are you using?
Photos of the motherboard needed. Biostar loves to use OST caps in their boards. These caps are known to fail without any visual signs.

[DankEngihn]

Re: Biostar U8668 Grand power issues

We need more info and photos. What PSU are you using?
Photos of the motherboard needed. Biostar loves to use OST caps in their boards. These caps are known to fail without any visual signs.

I tried two known-working power supplies. A Bestec ATX 12-Z, and an Enermax EG365P-VE. Both shut off after a few seconds. I found that if I use an SDRAM stick, it stays on, but gives me an erratic series of high and low pitched beeps.

[Sparkey55]

Re: Biostar U8668 Grand power issues

I tried two known-working power supplies. A Bestec ATX 12-Z, and an Enermax EG365P-VE. Both shut off after a few seconds. I found that if I use an SDRAM stick, it stays on, but gives me an erratic series of high and low pitched beeps.

When using SDRAM as opposed to using DDR RAM about how longer does the mobo stay on? The Hi/Lo siren usually means overheated CPU.

[DankEngihn]

Re: Biostar U8668 Grand power issues

When using SDRAM as opposed to using DDR RAM about how longer does the mobo stay on? The Hi/Lo siren usually means overheated CPU.

It stays on until I shut it off manually. The CPU ccan't e overheating because the siren starts almost intantly, before the CPU would have time to get hot enough to overheat.

[Sparkey55]

Re: Biostar U8668 Grand power issues

When you have a stick of SDRAM installed does the it beep a code?
with an Award BIOS the alternating Hi/Lo sound indicates a CPU problem and a constant BEEP-BEEP-BEEP... means Memory problem or voltage issues.
it seems that you could have an issue with the 2.5V regulator for DDR ram since the board stays on with the SDRAM inserted. SDRAM would be using 3.3V directly.
You could have bad caps around the ram slots or any where else for that matter.
Please take a few photos of the board caps. What are they?

[DankEngihn]

Re: Biostar U8668 Grand power issues

The caps all look fine physically, and they are OST caps. Yes, it does the beep code with a stick of SDRAM. With DDR RAM, it powers on for a second, then shuts off.

[Sparkey55]

Re: Biostar U8668 Grand power issues

The caps all look fine physically, and they are OST caps. Yes, it does the beep code with a stick of SDRAM. With DDR RAM, it powers on for a second, then shuts off.

Well, if you read enough of this forum by now you should know about how bad OST branded caps are in motherboards. That board is dated with original caps. If it was me I would eradicate all of the OST caps above about 470UF then troubleshoot if needed. Also there are bad aging caps in the Enermax PSU too.

[DankEngihn]

Re: Biostar U8668 Grand power issues

Alright, so here's an update. The board seems to now have some signs of life. The board no longer shuts off after a few seconds, wether I use DDR RAM or SDRAM. I still get the CPU siren thing though.

What's more reassuring that the board somewhat works, is that if I power it on with NO ram, I get a long continuous beep, indicating a memory problem.

So at least the board somewhat works