Motherboard powering on with no video output

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Motherboard powering on with no video output

Postby Elia1995 » Thu Jul 07, 2016 1:42 am

Hi, recently I wanted to revive my 2005-2006 PC with the Abit NF7 motherboard, I did the main things, such as removing the CPU and cooler, cleaning them very well, mounting them again, checking the DDR1 ram on another motherboard if it works, I then proceeded to clean the PCI and AGP slots very well and, of course, getting a new 2032 coin battery for the CMOS.

All of that leaded to the first ever powering on after roughly 10 years: I heard a "bang" the first time and I immediately shut it off... well, nothing seemed to be happened, must've been a capacitor... oh well, I then powered it again and since then now it always powers on without problems, it goes, it's loud as hell but keeps staying on... but it has a huge problem: NO VIDEO.

I tried with every AGP card I have and with the S3 Virge (PCI) card, I get no video whatsoever, but the board "works", I mean it powers on and stays on...

what can the issue be ? I want to fix it whatever it takes, it's the last AGP motherboard I have and I NEED an AGP motherboard for a fully working Windows 98 retrogaming PC.
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Re: Motherboard powering on with no video output

Postby Karlsweldt » Thu Jul 07, 2016 5:49 am

Look over all the capacitors carefully. Any that have domed tops, lean excessively or have leakage are bad. If one shorts internally, it could explode, sending caustic material about. The PSU is not immune from the "bad caps" syndrome.
One other possible cause of that 'bang' may be a voltage regulator near the CPU. Small, square items about 1/2" square. Any that look 'toasted' have gone bad.
As to the problem of self-starting, could only be a BIOS control about power settings. Typically a choice of "stay off", "restart" or "last state", for when power is lost.
AGP cards have to match the slot type. Damage can ensure if the video card and slot are mismatched. https://en.wikipedia.org/wiki/Accelerated_Graphics_Port

Win 98SE was the "last of the breed" to have a true command-prompt mode. But Win 98 will work with newer than AGP video. The only requirement of the video card is that it can be compatible with older game needs. Sound formats may require an IRQ of 5 or 7 only.. which newer audio features may not have.
For some older games, consider the ZDOOM engine, which will work with *.wad files in games such as Doom and Heretic.
http://zdoom.org/News
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Re: Motherboard powering on with no video output

Postby Elia1995 » Thu Jul 07, 2016 1:58 pm

On my main PC (and the most modern I currently have), I play Doom and other doom engine-based games with GZDoom.

On the Abit NF7 motherboard there is a bulged cap near the AGP slot, do you think that changing this capacitor the video might work again ? There are no burnt resistors near the socket anyway.
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Re: Motherboard powering on with no video output

Postby Karlsweldt » Thu Jul 07, 2016 3:36 pm

"Bulged cap".. definitely bad! More info about the 'bad caps' syndrome at http://www.badcaps.net/
Replacing it is easy enough, if you have decent soldering skills. A bit of braided copper wire should suck most of the solder away, and the bad capacitor can be removed. Replace with the exact same value and voltage, ensure it is rated at 105°C. Low ESR rating would be preferred. 50% chance it may resolve the issue as long as no other faults. Have recapped several motherboards, 90% success rate.
On the motherboard, under the capacitor, look for a diagram of the polarity for it. Typically a small circle, half white or black with the + and - symbols.
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Re: Motherboard powering on with no video output

Postby evasive » Sun Jul 10, 2016 12:22 am

NF7 rev 1.0?
If so, replace ALL capacitors with a value >47uF
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