First post, by RogrWilco
Hi folks. My 486DX2/66 build is only posting intermittently. I would appreciate any advice, since this is my first retro build. Happy to provide info and pics re components, too, if it'll help.
I'm using a SOYO SY-25N mobo and a 486 DX2/66.
When powered on, the power supply fan always starts and the hard disk, if connected, always spins up. Good signs.
With just the CPU installed and no other components, I'll almost always hear a series of beeps. Again, good sign. However, on occasion I won't get any beeps even with just the CPU installed.
When I go ahead and install RAM and the graphics adapter, the system will either beep once and successfully post or there will be no beeps at all and no video signal. When there are no beeps, I have to repeatedly power cycle and it will always eventually post. Once it successfully posts once, I can usually restart or power cycle and it will continue to successfully post (not always, however). But if I power off and leave it for a few hours then come back, it will usually fail to post again (ie. no beeps). I then have to power cycle repeatedly again to get it to work (which it always eventually does).
I've tested the power connector and, with no load, the 5V rail is out by 7% and the others by less. I've pulled the BIOS chip, cleaned the contacts, and reseated it. I don't know what else to do. I wonder if it's a problem with a capacitor in the power supply or on the motherboard because the computer, once working, fails to post again if left off for some time. However, inconsistent with this theory, it sometimes (though more rarely) will fail to post even if it had successfully posted a few minutes ago.
I don't have any spare parts to swap in to test which components might be the problem, though I'm happy to buy a replacement once I figure out the source of the problem. I really like this motherboard though with its ZIF socket and 3 VLB slots and would like to save it if I can. I have a multimeter and would really appreciate it if someone could suggest further trouble shooting steps. I'm happy to post pictures of any of the components, too, if it'll help. Thanks a bunch!