I can't help you much with the monitor, maybe the grid is magnetized, or just one color component cable is somehow disconnected internally?!?

Though I have a Compaq Presario CDS520 setup as retro rig and it runs fine.
Don't delete the installed MS-DOS since it has Compaq specific modifications f.e. using the mode command.

I have the detailed config published here: http://mail.lipsia.de/~enigma/neu/retropcs.html

Bad soldering joints at the tube socket were a common cause. Is green missing completely?

I slid the motherboard tray out and followed the cable from the monitor to the board. I made sure the plugs were pushed in properly and when I turned it on again the colors was fixed. The problem now is that the screen is too far to the right. Even if I try and use the horizontal control it won't center the screen. I wonder how that could be fixed?

Sounds like your monitor needs to see a TV technican.

Opened up the case out found some tuning screws for the horizontal and vertical settings. I played with these and now the screen is centered and the right color!

Does anybody know what the on-board sound on this thing actually is? I have been looking for some specs on the CDS 520 but have been finding it difficult to find anything. I think the CPU is a 486 DX2 66. I would like to put by AMD 486 DX4 100 in there if possible. I already upgraded the RAM from 8MB to 64 MB.

Why not just pull the motherboard out and look at it? That'd tell you exactly what all the specs are.

There is nothing written on the MB that looks like the model. It has "Sun Valley" and "177067-001" on it but they didn't help when searching. I did find a PDF (see attached) with a bit of info on it, but it has nothing about the on-board sound or other details.

Edit * Just looked at the link that elianda posted above and it does say the sound is ESS 688. I know nothing about this sound device. I assume it's Soundblaster compatible?

Does anybody know if the ESS 688 is Sound Blaster compatible?

Try the ESSCFG utility in this zip, I think it's SB Pro compatible.

I think NSSI would help you determine what hardware that computer has http://www.navsoft.cz/products.htm

EDIT: Or PC-Config http://www.holin.com/cindex.html

Thanks guys. You have been a great help.

Sorry, another question. I wanted to try and put in a DX4 100MHz CPU. I took the heat sink of the existing one but I don't seem to be able to remove the CPU. Is it possible that it is soldered in?

Nah, more likely that the paste has cooked itself stuck. Put it in the freezer or use a heatgun, if it's stuck good (or you're impatient) you can try to pry it apart with a flatbed screwdriver (you can use an old credit card to prevent the CPU from getting scratched if you want to).

And if you have doubts, you can post a pic of it here 😉

Might have to post a pic. It's not the heat sink that is attached to the CPU. It is the CPU that is attached to the socket and won't come out.

You'd better try to find the system's specs to confirm that it can have a dx4 100. I assume that the dx2/66 is a 5v cpu, as opposed to the dx4 which is a 3.3v cpu. If it's like that, and it can't have any 3.3v cpus, and unless you have a voltage regulator, it might be better to leave it as it is... 😀

Yeah, I have decided to leave the CPU as is.

Actually the CPU is a AMD 486SX2-66.

in that case a dx2 66 is probably an drop in no change replacement at least. a fpu can be nice to have in a 486.

swaaye wrote:

in that case a dx2 66 is probably an drop in no change replacement at least. a fpu can be nice to have in a 486.

Well, as I said earlier. I can't get the CPU out of the socket. Not sure if it's soldered in or something. I would like to be able to get it out though.

It's doubtful that the CPU is soldered in... more likely it's one of those so-called "low insertion force" sockets, which are rather counterintuitively named since there's nothing low-force about them. It can take quite a bit of prying to get the CPU out of one of those... there were even special 486 extraction tools made for the purpose.