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Troubleshooting VLB

Hatta

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May 27, 2010
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I bought a dead 486 in the hopes that I could use the case and some of the parts inside. Of interest was the Diamond Stealth 64 DRAM T VLB, so I got a UMC based VLB motherboard to replace the dead one. Unfortunately, the new board refuses to so much as beep with the VLB card in it. The new board works great with a 16 bit ATI VGA Wonder though. I tried giving the card a good cleaning with deoxit and qtips, no luck. I tried setting the wait states in both positions, with both jumpers and the bios. I tried disabling video rom shadowing. I couldn't find anything else that looked relevant.

I've read that VLB can be difficult, is there anything I can do about this? Is the card likely to be dead or just incompatible with my motherboard? Should I avoid an S3 based VLB card if I buy a replacement? I was under the impression that these S3 cards were second best for DOS, after Tseng cards. If I don't want to pay ebay prices for a Tseng, what's a good third place option?
 
What is your bus speed? If it's 40 or 50 MHz it may be too fast for the card. ARK Logic 1000 and 2000 are also fast DOS chips.
 
I'm running a plain old DX2/66 at 33FSB. I even tried dropping it to 25. I'll put ARK on my list of chips to look for. Thanks.
 
I wonder if it might just be something simple like a shorted tantalum cap, or dirty contacts on the BIOS or memory chips... You may also want to give the VLB contacts a good wipe-down with some alcohol.
 
I'll have a look at the caps under a magnifying glass tonight. I've never tried cleaning the pins in a card slot before, but I suppose it's worth a shot.
 
I bought a dead 486 in the hopes that I could use the case and some of the parts inside. Of interest was the Diamond Stealth 64 DRAM T VLB, so I got a UMC based VLB motherboard to replace the dead one. Unfortunately, the new board refuses to so much as beep with the VLB card in it. The new board works great with a 16 bit ATI VGA Wonder though. I tried giving the card a good cleaning with deoxit and qtips, no luck. I tried setting the wait states in both positions, with both jumpers and the bios. I tried disabling video rom shadowing. I couldn't find anything else that looked relevant.

I've read that VLB can be difficult, is there anything I can do about this? Is the card likely to be dead or just incompatible with my motherboard? Should I avoid an S3 based VLB card if I buy a replacement? I was under the impression that these S3 cards were second best for DOS, after Tseng cards. If I don't want to pay ebay prices for a Tseng, what's a good third place option?

Some VLB's have a jumper associated with the slot. That doesn't appear to be the case for your mobo according to the Stason . If the system works with with an ISA video card then I would greatly suspect the VLB has some problems. I don't suppose you have access to another VLB mobo? VLB video cards are all over the place - you shouldn't have to much trouble finding a replacement here on the forum for a reasonable amount.
 
You may also want to give the VLB contacts a good wipe-down with some alcohol.
Not only that but I've found, over and over, that VLB cards are especially difficult to seat. Many times I've put a card in and had to take it out (sometimes more than just once) and reseat it until the board/VLB card were happily mated.
 
I closely examined the capacitors on the card, cleaned the VLB slot with deoxit on a paper towel on a plastic card, and reinserted several times. No luck. I'm calling this card dead and looking for a new one. Please have a look at my post in the wanted forum.
 
The only type of capacitor failure I'm familiar with is bulging electrolytics. Would a shorted capacitor not be visible by examining the solder joints on the legs to see if they're touching?
 
The only type of capacitor failure I'm familiar with is bulging electrolytics. Would a shorted capacitor not be visible by examining the solder joints on the legs to see if they're touching?

No, when the short, they short internally, you need to check them with a multimeter.
 
S3 chipsets for VLB are generally pretty good. But I don't know about the Trio chips. I think the Trio32 and Trio64 were primarily designed for PCI with VLB support as an afterthought (speculation). If you look for Trio VLB card related posts in the google newsgroups you can see there are many issues with them.

The ARK1000 based cards are indeed quite fast in DOS, but they are not so great for Windows. Personally I'd go for an ET4000W32P based card. I've tried most of the VLB VGA cards out there and so far I like this one best.
 
I solved this problem. After getting another VLB card from Stone, the computer would still not boot. So I went back to the diagram and examined every jumper. Turns out J2 was set to pins 1&2, which should only be the case if there's a 486DLC in the board. This had no functional consequences for my system, except for totally breaking VLB.

So for those who face a similar problem in the future, check every jumper. Even those that don't seem related.
 
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