Computer motherboard question.

Factual Questions
1

I’m trying to build an older computer, and by older, I mean a 486 (don’t ask why, I just am) but am having a problem. I’ll give all the details about the motherboard, memory, cards, and so forth, in hopes that this will help someone identify the problem and be able to give me a solution.

First, I have two motherboards that I bought a while ago off of eBay, one, a 486 VIP - (V)LB(I)SA§CI (It has 1 VLB, 3 ISA, and 3 PCI ports). It has an overdrive chip which allows to run at the speed of a Pentium 75mhz. It has two banks of 2 sets of 72-pin SIMM slots for memory.

Next, is an old Pentium with a 75Mhz chip. It has 2 VLB slots, 2 ISA and 4 PCI ports. The memory is kind of funny. There are three 72-pin SIMM slots and 4 30-pin SIMM slots, which can be used in a variety of combinations for various amounts of memory.

OK, now, I’ve heard one way to test a motherboard is to simply hook up the power, take out any cards, and just start it up. It should give warning beeps that there’s no video, or keyboard, or whatever. I get no warning beeps.

For both motherboards, I hook up everything, a hard drive, floppy drive, CD ROM, video card, and memory, and turn on the computer. It makes the sound like it’s checking the memory, but this can’t be since it makes the same sound if I take out the memory and turn the computer back on.

I also see the access light flicker for a second or two when the computer turns on, but no attempt seems to be made to access either the hard drive or floppy (the hard drive is from eBay, the floppy is brand new)

And the screen is blank. No boot up screen, no error messages, nothing. And it’s not the video card, which is a 4 meg VLB video card. I know this, because I tried using another video card and still got a blank screen.

It could a damaged motherboard, but since both motherboards act the same, I’m not so sure. I’ve tried disconnecting various cards and restarting the computer, every time with the same results. I’m nervous about bringing to any kind of computer shop as the components are very old now, and most people only want to work on, or only know how to work on modern computers.

Yes, this is basically a hobby, but I’ve already spend a good deal of money on the parts (a 4meg VLB card is very rare and I ended up paying about $50 for it a few years ago) and don’t want to give up and feel like I’ve blown my money for nothing.
So, before giving up, using some of the parts on my other computers and either trashing the rest, or trying to resell them on eBay, I’m hoping that somebody has some hints and/or solutions. Thank you.

2

It could be a power supply issue. Have you tried these boards with a different PS? If that’s not it, there’s a good chance that both boards are shot. The most likely culprit, given the age of the boards, is one or more dried-out electrolytic capacitors.

3

I had a minitower with a power supply. I first tried the motherboards with that. With nothing else attached. Nothing was happening, so I thought that the power supply was bad. I bought a new one, same thing.
So, I threw out the case and power supply, bought a minitower with a power supply included. Same thing. Actually, I found out that hooking things up to the motherboard actually made things seem more normal, except that nothing still appeard on the screen and the hard drive and floppy drives aren’t being accessed.
Hmmm, bummed out now. If I buy another motherboard to test that theory, I waste money, especially if it turns out that the mother boards I have aren’t shot. And if I just give up and throw out my computer cards and other parts (or try reselling them on eBay and probably get a fraction of what I paid for them), then I wasted money by having parts that I never got to use.
Anyway, I guess this is a possibility. Thank you.

4

I play around with vaxes and PDP-11’s occasionally. A 486 isn’t old. :wink:

Careful about these. Sometimes there are some really goofy rules about which combinations it will allow.

This isn’t necessarily true for older motherboards. A lot of them won’t beep. Most of them will only start beeping if they have a processor and memory that are all functional.

That might be the sound of the hard drive spinning up and doing some initial checks. It might also be the sound of it checking for memory, but finding none. Generally speaking, leave the drives attached to the power supply (so that you maintain a minimum load, otherwise the power supply might auto shut off) but leave all of the drives disconnected from the motherboard until you at least have the POST display on the video. Then add things one at a time.

That’s probably just a power up state, not a true disk drive access.

Don’t go spending a lot of money on 486 parts. This is stuff that you can generally find for $1 a box type of thing.

Send me an e-mail if you can’t get these things going (I think one of my email addresses is in my profile). I’ll see what I can do to help you out.

5

Wow, somebody else who plays with older computers, cool :slight_smile:
OK, when I say that I’ve spent a good deal of money on parts, I mean a good deal collectively. The VLB video card was the most expensive individually.
Also, I’ve wasted money throwing out cards or parts that I thought were bad, buying new ones, only to find out that the old ones were OK, like buying two new power supplies because when hooking up the supply to a motherboard with nothing attached, made the power supply seem week, and I didn’t realize that you need to also have things like a hard drive hooked up as well.
It could be the memory chips, but still, would I get a POST start up screen telling me that there’s a memory problem?

6

Oh, and thank you for your offer to help. I may take you up on it, once I’ve convinced myself that I’ve tried everyting that I can and nothing still works.

7

I usually just put the video card & memory in & start with that. It should show something on the screen. Are you using pairs of chips? Also try filling the memory chip banks up.

8

I do fill up all the memory banks. Anyway, as this thread goes on, I’m beginning to believe more and more that it is the motherboard, actually both motherboards, since there’s no POST screen and I know that both the video card and the monitor are both fine, and I’ll have to get a new one if I want to continue my little project.

9

Well, I’m kind of in luck. I found on eBay the exact motherboard I’m using
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=3432593403&category=1244
So I guess I can bid on that. Hey engineer_comp_geek, if you know how I can get this kind of motherboard for cheap, let me know :slight_smile:

10

E-frigging-gad. It’s a PCChips MB! No wonder it doesn’t work.

Do not buy this board. Never buy a PCChips MB. (And stay away from relabelers that sell them like Amptron.)

Now here’s the really weird part. Someone (at this time) has bid $8.95 for this. What??? Good socket 3 MBs are not even worth a dollar!

Wow, I have a box of 486 MBs in the basement (and some VLB cards too). Maybe I can make some money on eBay. But I would still feel like I’m taking money from suckers.

Joel, there are thrift stores all over town. Go to a big Goodwill or whatever. Get a whole 486 system for $10. (Or wait till the 50% day and save even more.) Go to garage sales, buy a box of computer parts for a dollar.

11

One guess as to who made the bid :smiley:
See, I want that motherboard because it has a VLB socket, ISA sockets and PCI sockets, and VIP motherboards seem somewhat rare. And I don’t want to buy a system, because this is a hobby where I’m building a system. Buying a system would defeat the purpose.
And yes, I already have Pentium. In fact, I have a couple of them, but I want the 486 for a couple of reasons.
Two main ones are, I spent a ton of money on a VLB video card a few years ago, and I don’t want to have to throw it out, or sell it for a fraction of what I paid for it. Also, I have an AITech TV tuner, which only seems to work my VLB video card. I tried using it with the PCI cards of my other computers (Yes, I said PCI not AGP) and it doesn’t work.
There are other reasons why I want it too. The description said that it was working when last used. The board I have now was sold by somebody who has a ton of different kind of motherboards and he didn’t know the condition of any of them, so of course, I got that one cheep.