Looks great!

Sweet little time capsule you have there 😀

When PCs get to a certain age (and this one definitely does) the things that start to go are:
- CMOS battery. Most systems of this age have soldered Varta barrels that leak corrosive fluid over your motherboard. This system thankfully has an external battery mounted on the side of the PSU. If it's dead, replace it, but the only suggestion might be to relocate it to somewhere not immediately above the motherboard PCB just in case it might leak at some point in the future (I once obtained a Tulip 286 where that had happened over the motherboard. It wasn't pretty - or fixable)
- electrolytic caps. They can bulge, burst or just quietly fade away - but they fail open, so generally not a risk for anything else. If that happens, just replace with similar low ESR caps.
- tantalum caps. If it sounds like someone let off a gun in your computer, you just met a failing tantalum cap - which incidentally is a good reason to wear glasses when powering up old hardware for the first time. They also fail short, so invariably prevent the computer from running and can cause other damage on the way down. As the computer is now working, the tantalum caps (which are definitely present, I can see a couple in your pics) are OK - for now. The only way of avoiding this is preventive replacement, but given risks of that I'd not do so unless you're very confident and have the right tools.
- rubber bands in floppy and CD drive. Rubber or whatever synthetic alternative is used degrades; it either dries out or turns into tarry muck. If drives get unreliable this is a prime cause.

Yellowing ABS plastic is a fact of life for old systems. You can temporarily reverse that with retrobright, but it will yellow again with time. That missing keycap is a shame. It's worth looking out for a replacement. What sort of switches/mounts does the keyboard have? The general layout looks like an Alps Bigfoot design, but I'm not sure that visible switch/mount is Alps.

dionb wrote on 2025-10-13, 09:51:

Sweet little time capsule you have there :) […]
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Sweet little time capsule you have there 😀

When PCs get to a certain age (and this one definitely does) the things that start to go are:
- CMOS battery. Most systems of this age have soldered Varta barrels that leak corrosive fluid over your motherboard. This system thankfully has an external battery mounted on the side of the PSU. If it's dead, replace it, but the only suggestion might be to relocate it to somewhere not immediately above the motherboard PCB just in case it might leak at some point in the future (I once obtained a Tulip 286 where that had happened over the motherboard. It wasn't pretty - or fixable)
- electrolytic caps. They can bulge, burst or just quietly fade away - but they fail open, so generally not a risk for anything else. If that happens, just replace with similar low ESR caps.
- tantalum caps. If it sounds like someone let off a gun in your computer, you just met a failing tantalum cap - which incidentally is a good reason to wear glasses when powering up old hardware for the first time. They also fail short, so invariably prevent the computer from running and can cause other damage on the way down. As the computer is now working, the tantalum caps (which are definitely present, I can see a couple in your pics) are OK - for now. The only way of avoiding this is preventive replacement, but given risks of that I'd not do so unless you're very confident and have the right tools.
- rubber bands in floppy and CD drive. Rubber or whatever synthetic alternative is used degrades; it either dries out or turns into tarry muck. If drives get unreliable this is a prime cause.

Yellowing ABS plastic is a fact of life for old systems. You can temporarily reverse that with retrobright, but it will yellow again with time. That missing keycap is a shame. It's worth looking out for a replacement. What sort of switches/mounts does the keyboard have? The general layout looks like an Alps Bigfoot design, but I'm not sure that visible switch/mount is Alps.

Thank you for the help! I'm not sure about the switches on the keyboard. I've uploaded some pictures of them and the back of one of the other keycaps. As for the Varta battery, I've actually taken this out already to try and avoid corrosion and because the BIOS had a password on it. I haven't been able to replace it yet, though.

CardboardDeath wrote on 2025-10-13, 15:33:

[...]

Thank you for the help! I'm not sure about the switches on the keyboard. I've uploaded some pictures of them and the back of one of the other keycaps. As for the Varta battery, I've actually taken this out already to try and avoid corrosion and because the BIOS had a password on it. I haven't been able to replace it yet, though.

That is an odd one... does the keyboard have a brand and model (on sticker underneath)?

Looks like a Sound Blaster 16 CT2230, which is one of the better SB16 models. Real OPL3 and somewhat fewer issues than other SB16 models (though not perfect of course). Probably a Sony interface CD-ROM drive as well, judging from where it's connected to the card.

Also, that's a really nice system and a great way to get into retro computing. Congrats on the find. 😀

dionb wrote on 2025-10-13, 18:32:

CardboardDeath wrote on 2025-10-13, 15:33:

[...]

Thank you for the help! I'm not sure about the switches on the keyboard. I've uploaded some pictures of them and the back of one of the other keycaps. As for the Varta battery, I've actually taken this out already to try and avoid corrosion and because the BIOS had a password on it. I haven't been able to replace it yet, though.

That is an odd one... does the keyboard have a brand and model (on sticker underneath)?

The brand is NMB technologies. Here's the sticker on the underside.

CardboardDeath wrote on 2025-10-13, 19:05:

[...]

The brand is NMB technologies. Here's the sticker on the underside.

OK, that's a familiar name. NMB is famous for its Hi-Tek keyboard division and its 'Space Invaders' mechanical switches. And there are definitely versions of the RT101+ that have them. But your board doesn't have space invader switches, which is bad news for two reasons:
1) you probably have a squishy rubber dome membrane under that board
2) bizarrely, NMB seems to have chosen a completely different keycap mounting system for their dome-with-slider boards vs the mechanical space invaders. So the only source for that missing keycap would be another NMB RT board with dome-with-slider mechanism.

So that might be something of a challenge.