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Old 08-14-2021, 07:10 AM   #1
EFritz20
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Default [Retro] Asus A7N8X Deluxe Rev2.0 Power issue related to caps?

Hello all,

I have had this motherboard for a long time and started trying to use it again.
As alot of you know its a Socket A(462) motherboard from the bad caps era.
Mine contains Rubycon MBZ 3300uf as VRM in and output. The caps look fine from the outside but the board itself has this problem;

If i turn the power off (completely unplugged for >30min) and then turn it on, the board will post just fine and i'm able to go into BIOS, modify it, save it and actually boot from it. Earlier I was able to install Windows on it, but now, just before it goes into the Windows desktop the monitor goes into standby.

When i turn off the machine and turn it on again (with power still connected), no matter how many times, the monitor will stay in standby. It won't give me a POST beep and the motherboard voice is quiet. It only works again by completely unplugging it for >30 minutes and then turning it on again. This happends over and over again, even with the default bios values. I have tried everything related to GPU (tried multiple also PCI, also AGP with 12V), the PSU is a brand new corsair with 25A on 5v line (tried different ones, also old one with 30A), multiple CPU's (1800+, 2600+,3200+) and different DDR memory. I also tried multiple BIOS versions and all have exactly the same issue.

My theory is that the VRM caps are bad and/or out of spec even though they are not bulged. At the first "charge" they somehow work partially, but when finally charged they fail after turning off the system. I'm not an electronic expert but i'm wondering if its worth recapping to fix this. The first time ALWAYS boots the system (after unplugged 30min), and all boots after ALWAYS fail while keeping the PSU power plugged in. Restarting the system (reset button) at first boot is never a problem.

I know these boards have a big history but i could not find similar issues to mine using google. Have you ever seen this sort off issue? Please help.

Thanks for reading.

Last edited by EFritz20; 08-14-2021 at 07:14 AM..
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Old 08-14-2021, 02:52 PM   #2
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Default Re: [Retro] Asus A7N8X Deluxe Rev2.0 Power issue related to caps?

Are the rest of the capacitors on the board OST, KZG, or Taicon? Or are they Rubycon YXG or a non-KZG NCC series? If the board hasnít been entirely recapped yet, a full recap may help, especially if the brands arenít very good. I would be surprised if the aforementioned MBZ failed in this manner unless the board had a hard life. It sounds like you tried swapping out every possible component except the monitor. Did you try it in safe mode? Iím wondering if the pins on the motherboard power connector have oxidized or possibly worn out since, IIRC, those older Athlonís could draw quite a bit of power from the +5V rail on those older boards which power the CPU using the +5V output.
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Old 08-15-2021, 05:08 AM   #3
EFritz20
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Default Re: [Retro] Asus A7N8X Deluxe Rev2.0 Power issue related to caps?

About 95% off the other caps on the board are OST caps from RLS series and it hasn't been recapped yet. I don't want to spend alot of time and money for a recap just to get the same issue back.

Somehow I keep thinking it has to be VRM. If it was for instance the AGP caps or memory then i would have expected either some BEEPS or the POST Voice mentioning AGP videocard or memory failure or something similar, but i get nothing and if "the brain is dead" it can't do much else, although all fans keep spinning.

I tried a different monitor but with the same results. I tried safe mode but it reboots automatically just before it goes into the Windows desktop. When i shut it down and power it on again i get no monitor activity again like i mentioned in the first post.
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Old 08-15-2021, 07:25 AM   #4
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Default Re: [Retro] Asus A7N8X Deluxe Rev2.0 Power issue related to caps?

I would use a port 80H post card to see where the board stops in the POST process.
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Old 08-17-2021, 05:08 AM   #5
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Default Re: [Retro] Asus A7N8X Deluxe Rev2.0 Power issue related to caps?

I would not change the MBZ, not seen any of those fail on these boards.

The OST are usually hardy but would not discount those as possible problems, they do fail.

I would personally try something as daft as reflashing a later bios onto the board first, sounds a odd issue.
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