VOGONS


First post, by Radroadrunner

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Recently, I've been working on building a 486 machine with a AM5x86-133, 96 MB of RAM, and a ARK 2000 card, all on a PC Chips M919. I finally got all my parts in today and once I had everything installed, I flipped the switch. Only problem was that the power supply immediately switched off. I inspected my hookups and realized that I had set my left leg of my power supply such that there was one wire coming off from the power supply that was not connected. From a pinout point of view, I had just sent +12V down the +5V line. After unplugging everything except the CPU and PSU and readjusting my PSU hookup so it was correct, I tried again to see if it would beep any post codes. No dice. I realize that this motherboard is probably fried but I was curious if someone beyond my expertise(Ironic, I know.) had any insight to if this might be salvageable or not. Thanks in advance.

Reply 1 of 7, by feipoa

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I didn't quite follow how you hooked up the 12 V to the 5 V line. Nonetheless, since the PSU immediately turned off, wouldn't this have saved the motherboard from death? Seems like whenever I have the PSU turn off immediately, e.g. due to a short, the MB still works once I've unshorted the short.

Plan your life wisely, you'll be dead before you know it.

Reply 2 of 7, by Tiido

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I have one PSU that is super picky and it didn't not kill a motherboard when I one time accidentally swapped the two power connectors. It didn't turn on, within a second I flicked power switch to off, saw my mistake, reversed the cables and tried again and mobo was ok.

But in your case the motherboard has some important component fried. Turn it on and then touch all the components, see if anything gets really hot within a very short time (like within 5 seconds).

T-04YBSC, a new YMF71x based sound card & Official VOGONS thread about it
Newly made 4MB 60ns 30pin SIMMs ~
mida sa loed ? nagunii aru ei saa 😜

Reply 3 of 7, by derSammler

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If +12V was supplied to the +5V line, you can bet that some component(s) burned to a short or caused too high current flow, which caused the PSU to shutdown. Check the two large transistors near the CPU socket first (those with the heatsinks touching the VLB slot). From my experience, these die first in such situations.

Also, you could try to insert a 5V CPU and set the jumpers accordingly.

Reply 4 of 7, by Radroadrunner

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Just found that a resistor blew and replaced it. Motherboard works great now other than I'm getting noise through my Aztech card whenever it attempts to do a DMA for digital samples. Not sure if it's the card or board.

Reply 5 of 7, by Skyscraper

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Radroadrunner wrote:

Just found that a resistor blew and replaced it. Motherboard works great now other than I'm getting noise through my Aztech card whenever it attempts to do a DMA for digital samples. Not sure if it's the card or board.

I have a few motherboards that outputs garbage when the sound card tries to use the 16bit DMA channel. Configuring the sound card to always use the 8bit DMA channel fixes that and the only thing you lose (I think) is full duplex.

New PC: i9 12900K @5GHz all cores @1.2v. MSI PRO Z690-A. 32GB DDR4 3600 CL14. 3070Ti.
Old PC: Dual Xeon X5690@4.6GHz, EVGA SR-2, 48GB DDR3R@2000MHz, Intel X25-M. GTX 980ti.
Older PC: K6-3+ 400@600MHz, PC-Chips M577, 256MB SDRAM, AWE64, Voodoo Banshee.

Reply 6 of 7, by Frasco

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Some time ago, one of my PSUs died, leaving marks of burns in the AT power connector (exactly in the 5v pin direction
and another one adjacent), taking with her a LAPC-I. Now the sound card is presenting distortion during any fade out in music.
So yeah, overflow is a terrible thing. 😢
and I'm a dumbass for using any AT PSU I get my hands on...

Just install it on a different motherboard and do the 8-bit trick mentioned earlier to find out if your card is 100%.
I believe it's hosed. This sucks, specially in my ears and pocket. 😵

Reply 7 of 7, by Disruptor

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Radroadrunner wrote:

...I'm getting noise through my Aztech card whenever it attempts to do a DMA for digital samples. Not sure if it's the card or board.

What type of Aztech card is it?
Some of them are really noisy during HDD access.