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Diagnosing A Weird Intermittent Fault With My MMX 233 DOS Gaming PC


Ever since I bought this Pentium MMX DOS gaming PC, it keeps having weird intermittent errors where it refuses to boot and I need to open it up and reseat all of the PCI cards. It’s getting very frustrating!

Join me as I finally diagnose and repair this annoying fault once and for all. Is it the graphics card? The RAM? The motherboard? Or is it the previous owner…


Hey everyone, Rees here, and welcome back to ctrl-alt-rees.

Now this video is going to be ever so slightly different to my usual stuff for reasons that will become apparent very shortly - and the reason is because I’ve just got this PC off the shelf to do some video capture.

I like to use this PC for video capture because it’s a Pentium 233 MMX, and it covers all of that kind of early to late DOS gaming stuff, and the early 3D Windows stuff as well.

So for example - I used this in my S3 ViRGE video to capture every single S3 ViRGE optimized game that was released, quite a popular video on my channel.

That was the card that actually came in this PC when I bought it from ebay - and speaking of buying this PC on ebay, when it very first arrived it had a fault, and a very common thing when you get PCs through the post - I reseated the cards inside and that fault went away and it worked perfectly fine, but I’ve noticed that every single time that I’ve used it this fault seems to crop up, and I thought it was about time that I finally got this fixed once and for all.

So before we get stuck in of course just a quick demo of the actual nature of the fault - and it’s really, really obvious so I’ll just show you what’s happening when we go to turn this on…

…and I will just switch this off because obviously it is quite a noisy machine.

So I’ve got a long beep followed by three short beeps, and I’m sure that if I bothered to look that up it would it would tell us exactly what the problem is - but essentially the monitor isn’t pinging on and the PC isn’t booting past that point, which suggests that it’s potentially an issue with the graphics card.

But what is a surprise is the fact that pretty much every single time I’ve moved this, or left it standing, or put it on the shelf and got it back out again like happened today just to use it, this exact same fault manifests itself and I need to get the screwdriver out and reseat all of those cards.

So let’s take a look inside and hopefully it should be pretty obvious what’s actually wrong with this.

Now, I have my overhead camera rolling - hello overhead camera! - which of course we’ll use to take a look inside this when I actually do the work, but the problem isn’t necessarily obvious from this side.

So I’ll just take the case off…

…and it’s a little bit bent at the top, so just a wriggle - just a bit of a technique!

So as you can see, in there I’ve got the Orchid Righteous 3D Voodoo card, I’ve got the Matrox Millennium- Mystique, sorry - still in there, and my CompactFlash adapter, the sound card and all that.

If you’re interested in the actual hardware that’s inside this PC I’ll put a link to that S3 ViRGE video down in the description so you can take a look at that and take a bit of a closer look inside.

But if we turn this around the problem becomes more obvious from this side - and I think what I’ll do is I’ll switch to the overhead camera for this one - and here we go.

So if you’ve built PCs of this era with these AT motherboards you’ve probably spotted the problem immediately, and in my defense this is how it actually arrived.

This is how the previous owner actually put it together so i’m surprised it survived this long!

But perhaps - no judgment on their part - perhaps they just had to use whatever parts they had available.

But if we have a look at the back here we’ve got part of an what looks like an IDE connector or a floppy drive cable connector just kind of wedged in the back there.

Obviously I don’t want to try and pull that out in case I do any damage to the motherboard.

I already spotted that a while ago, but what’s really interesting are these standoffs or risers or - um, I guess that’s what you call them - these nylon pins that actually hold the motherboard securely in place.

Now, as you can see this one isn’t fitted properly - the small knobbly bit on the bottom is supposed to go into the metal slot.

This is completely the wrong type - that’s from a completely different style of case, I think that’s a later ATX one - and as we can see we’ve got some, well we’ve got two here that are unpopulated which just happen to be directly under where the graphics card is, and essentially what happens when this thing’s kind of knocked or when it’s left in storage for a while is the motherboard starts to sag and actually bend towards the outside of the case here, and it pulls away from the graphics card - and it pulls away enough for it to actually unseat itself and disconnect.

I had a bit of a job getting hold of these - the only set I could find were these.

There were some people selling them on ebay but they were usually pretty ridiculous prices for what they are, but I found this StarTech kit which just happens to have lots of very useful PC screws and things in it and - oddly enough for the year 2021 - it also has a load of these AT motherboard standoffs in it as well.

So what we’re going to do is we’re going to take all of this out, we’re going to take the motherboard out, and then we’re going to reinstall it properly - and that should be the end of this problem forever, and also of course will hopefully prevent any further future damage to the hardware.

So let’s go!

So a couple of interesting things that I’ve discovered just stripping this down - one being where that IDE connector came from.

As you can see, this one’s missing its back - now I don’t think I have any of these 40-pin cables to hand so i’m going to just have to put this back together very carefully and just make a note that I need to find one of those just to replace that one, but that does work fine so that’s not a huge issue, and that was at the motherboard end so obviously it’s been like that for quite a while and I just didn’t spot it when I replaced the internal hard drive with this CompactFlash solution.

The other thing that I’ve noticed that’s quite amusing - apart from the fact that this is only held in with one screw in the corner and I’ll try and see if I can do anything about that if the screw holes happen to line up right - is this heatsink, which is something I’ve never noticed before, and that’s only actually attached on one side.

So yeah, I’m not sure who cobbled this thing together but it’s actually worse than some of the PCs that I built back when I was a teenager, so that’s some quite good going there!

Anyway, let’s continue to get this motherboard out and see what we can do to rectify this problem.

So one thing that I’m not going to do - just because I don’t need to - is disconnect any of this stuff.

I don’t have the manual for this motherboard - I think these are pretty standard but they’re not really very well labeled on the board itself so I would hate to unplug all of this stuff and then have to mess around for ages trying to get it all back in to the right places.

So I’ll try to do this with those still connected.

It turns out I was actually wrong about the heatsink as well - it’s just a bit loose, but it seems to be in contact, and I have used this PC for extended play sessions with no sort of heat-related issues at all.

I think what I will do is I will source a new heatsink for this - I’m not sure if it’s not quite the right type for this CPU or if it’s just a bit bent and old and dodgy, but that’s something that needs replacing as well, so I’ll add that to the list as well as that IDE cable.

But the important thing is that this is out and we can now have a look at trying to put this back together properly.

So, first thing is this completely useless standoff here - as you probably saw, I had to squeeze that with the pliers to get that to come out because of the way it was wedged in there - I’m not even sure how they managed that - but that will be replaced with the correct type.

So let’s get these fitted and put this thing back together and see if it all works!

Now, because of the style of motherboard that this is - and I think it’s I think it’s a Baby AT form factor actually - and because of the way it fits into the case and the way that the mounting holes in the board line up with the slots in the case, this is the best that we’re actually going to be able to do here.

There isn’t one that corresponds with this back corner, but realistically that back corner is just dangling there and there aren’t any plugs that fit in there or anything that plugs in as far over as that, so that’s not going to be a problem.

There’s not going to be any strain on that in particular.

The main thing is that we now have the right kind of standoff installed in this hole, and we have two standoffs here where there weren’t standoffs at all before right by where the PCI slots- PCI cards slot in.

So that’s going to be a massive improvement.

Unfortunately there isn’t a hole here either, but that’s kind of directly under the CPU anyway so I don’t really foresee that being a kind of particular flex point.

So what I’ll do now is just put all of the components back into the case and put it all together as tidy as I can, and let’s get it fired up and see how well it works.

So some more good news - I’ve just had a rummage in my parts box and I’ve actually managed to find an IDE cable that isn’t broken!

It’s got a bit of a dent there but hopefully that’s fine.

But importantly, the connectors are all in one piece so we’ll give this one a go.

I did manage to retrieve the broken piece of plastic that was rattling around underneath the motherboard, but the tabs have actually broken off on one end so that’s not going to go back together.

But that’s fine, I can swap the cable for this one and hopefully that’s another problem sorted.

Right - so here is our PC all put back together, and I can already tell you that it was a massive improvement putting those PCI and ISA cards in - some actual solid resistance from the motherboard this time rather than actually flexing which is always a good sign.

So I’m hoping that this has sorted the problem and not made it worse or broken anything in the process.

So let’s just try and boot this thing up…

…OK, so that’s not gone entirely to plan.

Let me just take a quick look.

…a few minutes later…

Take two!

Here we go…

…there we go, perfect.

So that was just the IDE cable - I plugged it in the wrong way round on the CompactFlash adapter - an easy mistake to make.

It’s not marked at all so I guessed and it turns out I guessed wrong, but as you can see it’s now booting up as expected, it’s detecting all 256MB of RAM, obviously both graphics cards are working because it’s connected up with the pass-through from the Matrox to the Voodoo card there, and that’s going through to the monitor so we’ve got a picture on the screen.

That’s all working fantastically well so I think I will leave it at that for now, and that means I can carry on with the video capture that I need to do for the video that I’m working on.

So I hope you enjoyed joining me for this little fix - not the most exciting video in the world I suppose, but this kind of routine maintenance needs to happen and it’s all part of parcel of owning and running these old machines.

So thank you very much for joining me, if you enjoyed the video please give it a thumbs up, hit that subscribe button, and leave a comment down below.

So until next time…


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