Reply 23160 of 26791, by Thermalwrong
DeathRabbit679 wrote on 2022-11-16, 06:21:
I was fooling around with my new MT32. Then I went to insert a CD and discovered my CD-ROM on my Pentium 1 box is waving the white flag and won't eject any more, so my retro activity became attempting to yank it out, only to discover I'll have to remove the FDD and HDD to be able to remove a screw someone put in an unreachable location. Ran out of time to mess with it. So, ultimately, my retro activity was banging my head on my desk repeatedly.
Ouch, yeah actually using retro stuff can end up that way pretty often. I always end up finding new faults on my laptops when I start using them properly. Hopefully it should be relatively easy to replace the drive eject belt on your CD drive or you've got a spare?
I've had a PC Chips M919 sitting on my 'this needs testing' pile and finally got around to it. The two NPN transistors that make up the motherboards voltage regulator circuitry had holes burnt out in them - this board came to me in a junk lot and I'm guessing the CPU got put in backwards. Testing them somehow one of them still worked? But the other one had a gain of 10 instead of 280 so it's no good anymore.
The heatsinks were gone too so I had to improvise. From the good M919 board I have, I can tell the M919 uses either Toshiba 2SC3420 or NEC 2SD1691 which are BJT NPN transistors. I've used NEC D1691-Y transistors from China and while testing I found one of them was literally backwards? Instead of being ECB with the writing on the front, it was BCE with the writing on the front. I'm wondering if they're fakes or re-marked parts but they were cheap enough and I only needed 2 so it's fine.
It worked and didn't catch fire, but on starting the motherboard just gave code E1 or E2 which for an AMI win bios is not a valid code. Better than "--" codes at least.
Initially I was running the 5x86 133 without a heatsink and it was pretty hot so I jammed this big old Zalman fan on there, which is working great, now it's running stone cold. It's so heavy that it's not going anywhere.
Something notable about these PC Chips boards is that they use 1.2mm pcb thickness instead of 1.6mm and this means they're kinda flexy - there was a visible bend in the top corner of the motherboard with the fake cache chips and the UM8881F chip. The cache chips had some clearly loose pins so I squished the UM8881F chip onto the board with my hand and powered it then it started up.
To fix that I resoldered the UM8881F's pins and now it's working pretty well, even working with the cache stick I've got for the M919: