As part of extensive historical research I've been doing for a couple of years now, yesterday I reverse-engineered an instrument manufactured in my country in the early 1980s. Today I reviewed it, and I think I did it right.
The next one I will reverse-engineer is one named LOGICID-1, from 1982, for which I only have the circuit and a little information. It's missing some chips; two are BCD-7seg decoders; I'm not sure about the other three. I will try to fully rebuild it.
Unfortunately, very little remains of these instruments, which is why I'm doing this. I found one from the second generation for sale.

DudeFace wrote on 2025-05-18, 20:06:

dr_st wrote on 2025-05-17, 10:01:

I'm struggling with nVidia driver stability on my QX9650/EP45/GTX660/Win7 rig. Keep getting BSODs at random times, both while gaming and also during desktop as well.
Not willing to come to terms with the likely explanation that either the board, or the GPU, or both, are bad - currently experimenting with random driver versions.

gigabyte boards of this era are pretty reliable so i'd rule that out, i had a Q9450\G31M\4GB DDR2 800MHZ\GT640\WIN7, i had the issues you mentioned when overclocking, and it was down to the ram, when overclocking the ram was set to auto so it would increase with the cpu, it was generic 800mhz ddr2 and it didnt like going much above 800mhz also they werent matching sticks, i had to set the ram to one of the options in the bios that lowered it to 667mhz which sorted the problem.

In this case I already know the board has at least some problems (primary PCIe x16 slot glitches with different cards, and some of the PCIe x1 slots are problematic as well), so I cannot rule that out. The RAM is quality OCZ DDR-1066, and I've verified the BIOS settings re: speed and timings. However, as advised, I shall run an extensive memory test, to be sure.

Finished repairing and refurbishing my Olivetti PCS286..

Cool. I had this exact same model back in the day. Years after I moved out of my parents house I asked my Mom if I could pick it up but she told me she threw it out with the trash. 🙁

I do have a keyboard that goes with this model but I picked that up only 2 years ago or so as a nostalgia purchase. 😀

Edit: Found a not so good photo of it:

That's a pretty cool font on the key caps.

pan069 wrote on 2025-05-20, 11:49:

Cool. I had this exact same model back in the day. Years after I moved out of my parents house I asked my Mom if I could pick it […]
Show full quote

Cool. I had this exact same model back in the day. Years after I moved out of my parents house I asked my Mom if I could pick it up but she told me she threw it out with the trash. 🙁

I do have a keyboard that goes with this model but I picked that up only 2 years ago or so as a nostalgia purchase. 😀

Edit: Found a not so good photo of it:

The attachment PXL_20210421_215607677.jpg is no longer available

That keyboard is the only part of the system that I lack, funnily enough 😀

Well, looks like I’ve just learned another hard lesson.
Was messing around with a cheap old motherboard, checking CPU voltage, when the multimeter probe slipped off the CPU leg and shorted the Vcc pin straight to ground. Even though I was working under the microscope, my hand shook a bit — didn’t notice anything at first, but the smell of burning told me something was wrong.
Pretty sure the CPU is toast now. The board got so hot a GAL chip literally popped off the diagnostic board.
Kinda sad — I’ll probably never find out what was actually wrong with that motherboard. Not even sure the POST card made it through.
Anyway, learning by doing has its price. No big deal — on to the next one.

Susanin79 wrote on 2025-05-20, 15:32:

Well, looks like I’ve just learned another hard lesson. Was messing around with a cheap old motherboard, checking CPU voltage, w […]
Show full quote

Well, looks like I’ve just learned another hard lesson.
Was messing around with a cheap old motherboard, checking CPU voltage, when the multimeter probe slipped off the CPU leg and shorted the Vcc pin straight to ground. Even though I was working under the microscope, my hand shook a bit — didn’t notice anything at first, but the smell of burning told me something was wrong.
Pretty sure the CPU is toast now. The board got so hot a GAL chip literally popped off the diagnostic board.
Kinda sad — I’ll probably never find out what was actually wrong with that motherboard. Not even sure the POST card made it through.
Anyway, learning by doing has its price. No big deal — on to the next one.

Troubleshoot the motherboard 😀
This is your next assignment.

Finished the work on the 486. Add two heatsinks on the graphics card's DAC, retrobright the 1.44MiB floppy drive panel and remove the excess wire connected to the main switch.

dominusprog wrote on 2025-05-20, 17:51:

Finished the work on the 486. Add two heatsinks on the graphics card DAC, retrobright the 1.44MiB floppy drive panel and remove […]
Show full quote

Finished the work on the 486. Add two heatsinks on the graphics card DAC, retrobright the 1.44MiB floppy drive panel and remove the excess wire connected to the main switch.

The attachment 20250519_181644.jpg is no longer available

The attachment 20250519_142113.jpg is no longer available

The attachment 20250519_175936.jpg is no longer available

Nice! That floppy looks new! Those connectors without the boots give me anxiety, though, 🤣

I find it odd, yet exciting to see the same card I happen to have laying in front of me. From what I can see, they are the same model, but yours is still different. Does that S5606A-65 actually get hot?

Got a Tualatin 1133 today, and threw a somewhat funny combo with the working MSI 815EPT Pro I got from the board lot, 4x128MB RAM, and the X800 Pro from @Socket3.

Funny enough it was pretty smooth, although the Samsung 840 EVO SSD might be the one to take credit for that.

Major Jackyl wrote on 2025-05-20, 22:21:

Nice! That floppy looks new! Those connectors without the boots give me anxiety, though, XD […]
Show full quote

dominusprog wrote on 2025-05-20, 17:51:

Finished the work on the 486. Add two heatsinks on the graphics card DAC, retrobright the 1.44MiB floppy drive panel and remove […]
Show full quote

Finished the work on the 486. Add two heatsinks on the graphics card DAC, retrobright the 1.44MiB floppy drive panel and remove the excess wire connected to the main switch.

The attachment 20250519_181644.jpg is no longer available

The attachment 20250519_142113.jpg is no longer available

The attachment 20250519_175936.jpg is no longer available

Nice! That floppy looks new! Those connectors without the boots give me anxiety, though, 🤣

I find it odd, yet exciting to see the same card I happen to have laying in front of me. From what I can see, they are the same model, but yours is still different. Does that S5606A-65 actually get hot?

The attachment 20250520_171242.jpg is no longer available

Could be a different model RAMDAC and maybe gets warm at high res high refresh.

Major Jackyl wrote on 2025-05-20, 22:21:

Nice! That floppy looks new! Those connectors without the boots give me anxiety, though, XD […]
Show full quote

dominusprog wrote on 2025-05-20, 17:51:

Finished the work on the 486. Add two heatsinks on the graphics card DAC, retrobright the 1.44MiB floppy drive panel and remove […]
Show full quote

Finished the work on the 486. Add two heatsinks on the graphics card DAC, retrobright the 1.44MiB floppy drive panel and remove the excess wire connected to the main switch.

The attachment 20250519_181644.jpg is no longer available

The attachment 20250519_142113.jpg is no longer available

The attachment 20250519_175936.jpg is no longer available

Nice! That floppy looks new! Those connectors without the boots give me anxiety, though, 🤣

I find it odd, yet exciting to see the same card I happen to have laying in front of me. From what I can see, they are the same model, but yours is still different. Does that S5606A-65 actually get hot?

The attachment 20250520_171242.jpg is no longer available

Yes, it whitened pretty well. The main different between your card and mine is BIOS chip(s). The DAC gets fairly warm, so I've installed the heatsinks.

Modding day.
This card has annoying fan whine at full tilt in Win98SE. Card has full sensor set and Asus SmartDoctor tool to for setting custom fan profile, but it's WinXP+ only. So I installed WinXP just for Temp tuning.
At first I put there regular 2W resistor but it heated up ~50C. 5W ceramic one while bulky seems to be fine. 82Ω brought fan RPM down to ~4000RPM from 6000+ default speed.
Results: GPU core seems to be floating in low-mid 40-ies now under load. However hottest part is actually memory ~52C and back side mem chips are naked. Not sure where temp sensor is located.
I'm using my retro rigs in semi open bench inside shelf. So this mod might not be good for tight less ventilated cases.

I just finished a good amount of testing on my, new to me, Gigabyte Z370 HD3P and vanilla Windows 2000. This motherboard has a lot going for it including MPS multiprocessing support compatible with Windows 2000, a combined PS/2 port that supports a mouse and keyboard at the same time with a splitter, the ability to clock the CPU higher than the base clock for operating systems that can’t handle modern turbo modes, and plenty of expansion slots. Unfortunately, the board also has a lot of resource conflicts impacting PCIE-to-PCI bridges in MPS mode, so the legacy PCI slot doesn’t work with Windows 2000 so far (a shame since I want to use an Audigy 2ZS in that slot).

Despite the bridge issue, I found a bunch of PCIE devices that do work with the board and Windows 2000. My GTX 480 works perfectly, a Realtek RTL8111E card provides networking, and I have a 7-port USB 1.1/2.0 controller (with a Via chip) that doesn’t crash Windows 2000. It all works pretty well. For sound, I found a Realtek HD Audio driver (Release 2.74) that works with the board’s built-in audio chip (an ALC1220). Realtek HD Audio doesn’t provide the same features as the SB Audigy, but it will do for now.

So far, I’m pretty happy with this board. I’ve got a NVMe drive installed for Windows 7 64-bit, and a second, smaller NVMe drive installed temporarily for a future Windows 10 install until I get a larger NVMe drive. Windows XP runs like a dream on it, too.

Now I just need to swap out the processor from the i5-8400 I used for testing to my i7-9700k and then fit it all into a case.

Susanin79 wrote on 2025-05-20, 15:32:

Well, looks like I’ve just learned another hard lesson. Was messing around with a cheap old motherboard, checking CPU voltage, w […]
Show full quote

Well, looks like I’ve just learned another hard lesson.
Was messing around with a cheap old motherboard, checking CPU voltage, when the multimeter probe slipped off the CPU leg and shorted the Vcc pin straight to ground. Even though I was working under the microscope, my hand shook a bit — didn’t notice anything at first, but the smell of burning told me something was wrong.
Pretty sure the CPU is toast now. The board got so hot a GAL chip literally popped off the diagnostic board.
Kinda sad — I’ll probably never find out what was actually wrong with that motherboard. Not even sure the POST card made it through.
Anyway, learning by doing has its price. No big deal — on to the next one.

Ouch 🙁 Personally I use a current limited bench power supply @ 12v with a picoPSU to limit the damage that things like that can do, but yesterday even that wasn't enough!
In trying to test out a laptop floppy drive, this PicoPSU finally gave up and let the magic smoke out - just a faulty component but that n-channel MOSFET in the lower right was over 100C and let out the smoke:

It had been playing up for a while, not shutting off when I turned the AT power switch off, but yesterday it was going high current and the Single Board Computer it powers wasn't powering up. So I guess it just let go, hoping that replacing that MOSFET gets it back up and running but who knows. Now running a cheap clone picopsu that I got from a *coin miner last year, this little Advantech PCA-6751 has very modest power requirements.

The other day I fished out my Compaq LTE Elite 4/75CX which wasn't starting up any more because the hard drive was just clicking and not starting up properly. I didn't search for long but apparently it's fairly common, the Quantum Daytona / Quantum Go-Drive has rubber bumpers and they've degraded enough that the heads can't get out of the park position.

Opened it up and put some kapton tape on the rubber bumpers after removing that big magnet plate above the head-arm. It clanged a couple of times but the drive starts up having blown the dust out with a blower before reassembly.

I guess it should stay working for a while but this drive should probably just be replaced with a compact flash card instead.
After I put this back together, it works! It passes a full surface scan too so the drive itself is in good condition, but those bumpers could dissolve more still. Then I remembered I had another Quantum Daytona with a green label maybe 1/2gb capacity which wouldn't start up so I took that one apart as well, sadly while the rubber bumpers had also dissolved, the real problem was the heads were stuck to the platter and once I freed it up, maybe 2 of the 6 heads were broken off and the platter was badly marked so that's dead. Perhaps I should set it up as a display or something. Still, got one working 😀

Threw together a quick, dirty, and simple source selector so I can easily switch between the output of my AWE64 and PicoGUS on my DOS system.

Sure, I can buy one, but if I have the parts ... why not make it? Works perfectly and a lot cheaper. 😀

Thermalwrong wrote on 2025-05-25, 02:29:

Ouch :( Personally I use a current limited bench power supply @ 12v with a picoPSU to limit the damage that things like that can […]
Show full quote

Susanin79 wrote on 2025-05-20, 15:32:

Well, looks like I’ve just learned another hard lesson. Was messing around with a cheap old motherboard, checking CPU voltage, w […]
Show full quote

Well, looks like I’ve just learned another hard lesson.
Was messing around with a cheap old motherboard, checking CPU voltage, when the multimeter probe slipped off the CPU leg and shorted the Vcc pin straight to ground. Even though I was working under the microscope, my hand shook a bit — didn’t notice anything at first, but the smell of burning told me something was wrong.
Pretty sure the CPU is toast now. The board got so hot a GAL chip literally popped off the diagnostic board.
Kinda sad — I’ll probably never find out what was actually wrong with that motherboard. Not even sure the POST card made it through.
Anyway, learning by doing has its price. No big deal — on to the next one.

Ouch 🙁 Personally I use a current limited bench power supply @ 12v with a picoPSU to limit the damage that things like that can do, but yesterday even that wasn't enough!
In trying to test out a laptop floppy drive, this PicoPSU finally gave up and let the magic smoke out - just a faulty component but that n-channel MOSFET in the lower right was over 100C and let out the smoke:

The attachment IMG_6614 (Custom).JPG is no longer available

It had been playing up for a while, not shutting off when I turned the AT power switch off, but yesterday it was going high current and the Single Board Computer it powers wasn't powering up. So I guess it just let go, hoping that replacing that MOSFET gets it back up and running but who knows. Now running a cheap clone picopsu that I got from a *coin miner last year, this little Advantech PCA-6751 has very modest power requirements.

The other day I fished out my Compaq LTE Elite 4/75CX which wasn't starting up any more because the hard drive was just clicking and not starting up properly. I didn't search for long but apparently it's fairly common, the Quantum Daytona / Quantum Go-Drive has rubber bumpers and they've degraded enough that the heads can't get out of the park position.

The attachment IMG_6594 (Custom).JPG is no longer available

Opened it up and put some kapton tape on the rubber bumpers after removing that big magnet plate above the head-arm. It clanged a couple of times but the drive starts up having blown the dust out with a blower before reassembly.

The attachment IMG_6595 (Custom).JPG is no longer available

The attachment IMG_6597 (Custom).JPG is no longer available

I guess it should stay working for a while but this drive should probably just be replaced with a compact flash card instead.
After I put this back together, it works! It passes a full surface scan too so the drive itself is in good condition, but those bumpers could dissolve more still. Then I remembered I had another Quantum Daytona with a green label maybe 1/2gb capacity which wouldn't start up so I took that one apart as well, sadly while the rubber bumpers had also dissolved, the real problem was the heads were stuck to the platter and once I freed it up, maybe 2 of the 6 heads were broken off and the platter was badly marked so that's dead. Perhaps I should set it up as a display or something. Still, got one working 😀

Nice job with the hard drive! I have worked inside a couple of old hard drives (mainly MFM drives from the 80s) and to me it always seems like brain surgery... I'm worried that one stray bit of dust will cause me to lose all or part of some important bit of data. 🤣

Ozzuneoj wrote on 2025-05-26, 05:53:

Thermalwrong wrote on 2025-05-25, 02:29:

Ouch :( Personally I use a current limited bench power supply @ 12v with a picoPSU to limit the damage that things like that can […]
Show full quote

Susanin79 wrote on 2025-05-20, 15:32:

Well, looks like I’ve just learned another hard lesson. Was messing around with a cheap old motherboard, checking CPU voltage, w […]
Show full quote

Well, looks like I’ve just learned another hard lesson.
Was messing around with a cheap old motherboard, checking CPU voltage, when the multimeter probe slipped off the CPU leg and shorted the Vcc pin straight to ground. Even though I was working under the microscope, my hand shook a bit — didn’t notice anything at first, but the smell of burning told me something was wrong.
Pretty sure the CPU is toast now. The board got so hot a GAL chip literally popped off the diagnostic board.
Kinda sad — I’ll probably never find out what was actually wrong with that motherboard. Not even sure the POST card made it through.
Anyway, learning by doing has its price. No big deal — on to the next one.

Ouch 🙁 Personally I use a current limited bench power supply @ 12v with a picoPSU to limit the damage that things like that can do, but yesterday even that wasn't enough!
In trying to test out a laptop floppy drive, this PicoPSU finally gave up and let the magic smoke out - just a faulty component but that n-channel MOSFET in the lower right was over 100C and let out the smoke:

The attachment IMG_6614 (Custom).JPG is no longer available

It had been playing up for a while, not shutting off when I turned the AT power switch off, but yesterday it was going high current and the Single Board Computer it powers wasn't powering up. So I guess it just let go, hoping that replacing that MOSFET gets it back up and running but who knows. Now running a cheap clone picopsu that I got from a *coin miner last year, this little Advantech PCA-6751 has very modest power requirements.

The other day I fished out my Compaq LTE Elite 4/75CX which wasn't starting up any more because the hard drive was just clicking and not starting up properly. I didn't search for long but apparently it's fairly common, the Quantum Daytona / Quantum Go-Drive has rubber bumpers and they've degraded enough that the heads can't get out of the park position.

The attachment IMG_6594 (Custom).JPG is no longer available

Opened it up and put some kapton tape on the rubber bumpers after removing that big magnet plate above the head-arm. It clanged a couple of times but the drive starts up having blown the dust out with a blower before reassembly.

The attachment IMG_6595 (Custom).JPG is no longer available

The attachment IMG_6597 (Custom).JPG is no longer available

I guess it should stay working for a while but this drive should probably just be replaced with a compact flash card instead.
After I put this back together, it works! It passes a full surface scan too so the drive itself is in good condition, but those bumpers could dissolve more still. Then I remembered I had another Quantum Daytona with a green label maybe 1/2gb capacity which wouldn't start up so I took that one apart as well, sadly while the rubber bumpers had also dissolved, the real problem was the heads were stuck to the platter and once I freed it up, maybe 2 of the 6 heads were broken off and the platter was badly marked so that's dead. Perhaps I should set it up as a display or something. Still, got one working 😀

Nice job with the hard drive! I have worked inside a couple of old hard drives (mainly MFM drives from the 80s) and to me it always seems like brain surgery... I'm worried that one stray bit of dust will cause me to lose all or part of some important bit of data. 🤣

hehe, I'm not exactly operating in any kind of cleanroom environment so I'm definitely taking big risks. My view is these drives are on borrowed time anyway if they have to be opened up so I only do it on drives where it's no big loss if the drive dies - I have a puffer type of blower that I use to clean away visible dust to get it clean before the drive gets operated again.
I doubt it would work with drives over 1GB in size or with a faster RPM though

Ozzuneoj wrote on 2025-05-26, 05:53:

... I have worked inside a couple of old hard drives (mainly MFM drives from the 80s) and to me it always seems like brain surgery... I'm worried that one stray bit of dust will cause me to lose all or part of some important bit of data. 🤣

I've recovered several hard-drive over the years...

I don't think it's quite as risky as you might think, as long as you don't have any visible dust/dirt on it
(I usually blow them out with a mild blast from a "clean" air-compressor)

They aren't completely hermetically sealed, and do have air circulation, including a fine filter to remove
anything that "might get in".

If there is some too-small-to-be-visible stuff in the drive, chances are high that it will move off the platters
during the initial part of spin-up (before things are going fast enough to cause damage) and get absorbed by
the filter.

I once recovered a drive with severe enough "stiction" that there was a visible spot under the head.
Figuring "what the heck" I polished it up, re-assembled the drive - and it worked for several years after
(without bad spots). Re: Weird "scratch" sound from hdd