First post, by appiah4
Up until yesterday mine was a flaky hard drive that kept causing lockups that turned out to be a PSU issue where the HDD, CD-ROM and Floppy could not be supplied enough power from the same Molex chain. But yesterday, I finally solved an even stranger issue.
I was troubleshooting an AT Socket 7 system that was overall acting strange. Opening and closing the case would always result in a no-post reboot cycle - the PC would hard reset just as soon as it started giving me the POST Beep from the buzzer, but it would cut abruptly and reset. The issue would not go away until I pulled and reinserted a lot of random components, including IDE cables, power molexes, expansion cards - it would seemingly start at random and stop at random, there was no pattern to re-inserting what fixed it. I was almost certain it was a power supply issue, or a short between the board and the case. It took me literally months to find the source, and even then I was misled quite a bit.
A few weeks ago I finally tracked it down to the front panel connectors, and realized that if I removed the Reset button connector, the system would reliably POST! I was so smug and happy with myself, I decided that the Reset button must have been faulty and somehow gotten stuck from time to time. Until yesterday, when the weirdest thing happened. I would go into DOOM Setup and whenever I clicked on anything, the PC would reset. At first I thought it had to do with me replacing my ES1868 sound card with a CMI8330, because I was trying to go into the Music options when this happened, so I reverted to the old sound card but the issue persisted.
After a whole night of tearing everything down and putting it back together, formatting and reinstalling MS-DOS and Windows 98, I was about to throw in the towel and do away with what I thought was a broken ZIDA 5STX motherboard.. Then the the POST reboot cycle reoccured without the Reset Button header connected and I realized that the system reset itself whenever the buzzer beeped.. at certain frequencies!
So I wrote a program in GWBASIC that would beep at increasing frequencies and surely enough at a certain high pitched sound, the PC reset. I replaced the buzzer with a new one, and now EVERYTHING works fine, including the Reset Button. Who would know..
So how about sharing your weirdest troubleshooting experiences when dealing with retro computers/hardware?
Retronautics: A digital gallery of my retro computers, hardware and projects.