Compaq Prolinea 4/25S 486 25Mhz PC Repair & Resurrection

Jason Newman's computer projects

User avatar

Site Admin

Posts: 179

Joined: Sat Oct 29, 2016 2:06 pm

Post Wed Jul 12, 2017 1:03 pm

Compaq Prolinea 4/25S 486 25Mhz PC Repair & Resurrection

Quite a big project underway here.

I've been after a Intel 486 PC for years. They have shot up in value in the past 5 years (£100+ on eBay) and i didn't really want to invest that much into one.

Recently one popped up on eBay, a Compaq Prolinea 4/25S with known issues for £25. I put in an offer for £10 and won it! It is complete aside from hard disk and is a little rough needs a good clean but the major issue is the keyboard doesn't work on POST and apparently the CMOS battery has leaked so I expect the PCB tracks to the PS2 port are damaged. I will desolder the old battery ASAP and replace it with a modern CR2032 + adaptor and hopefully repair the traces on the board. If not it does have 2 serial ports so i may be able to get away with a serial keyboard or adaptor.

Here is the machine.

Image

Image

Image

I also plan to use a IDE to CF card plus adaptor on this machine I already have a Transcend 2GB SLC grade industrial CF card here and i've ordered an adaptor.

Image

With all that installed etc it should be good to go! Fingers crossed I can repair the traces if that is what the issue is.

More soon...
User avatar

Site Admin

Posts: 179

Joined: Sat Oct 29, 2016 2:06 pm

Post Sat Jul 15, 2017 1:10 pm

Re: Compaq Prolinea 4/25S 486 25Mhz PC Repair & Resurrection

Image

Had some parts arrive. The machine itself comes in a few days... Should be good!
User avatar

Site Admin

Posts: 179

Joined: Sat Oct 29, 2016 2:06 pm

Post Mon Jul 17, 2017 12:16 pm

Re: Compaq Prolinea 4/25S 486 25Mhz PC Repair & Resurrection

Ok the machine has arrived!

Image

Image

Image

Before even turning it on, it was straight into stripping it down for repairs and a much needed clean.

Image

The 486 SX processor. I thought it might have been soldered to the board but in fact it has a socket... 486DX/DX2 upgrade soon perhaps?

Image

ISA expansion module removed.

Image

Here is the big problem... a NiCD battery which is leaking like crazy.

Image

With the board removed i could see everything much better and it seems the underside of the board is fine. The top side shows signs of battery residue and some light corrosion on some of the components. Nothing too sinister though so far.

Image

Image

Time to get that battery out of here!

Image

Image

All gone! The eagle eyed of you may notice there is a cable running to one of the positive points on the board. This is in fact a cable for charging the battery. As i will be using a normal coin cell non rechargeable battery.. this charge cable can be removed.

Image

From here, it was out with the rubbing alchohol and q tips to clean the residue off the board.

Image

Filthy!

Image

Much cleaner, looking good now. I have spotted one exposed track but it doesn't seem to be broken from what i can see.

Image

Time to install the new coin cell battery!

Image

Image

Image

Installed ready for a nice new battery.

Image

After this i booted the machine up for the first time to ensure everything was ok.

Image

All good apart from the issues the seller described which was the keyboard not working. I checked the PS2 port and it does appear to be getting power so I'm going to assume it is that exposed track which is causing the problem. That track is likely the data feed from the PS2 port so i will need to repair that trace.

Image

Before that though, I've decided to get the case cleaned up so that when the board is repaired it has a nice clean home to go back into.

Image

Image

Image

Image

I also cleaned the PSU fan, it was caked in black crap.. I think this 486 was used in a warehouse of some kind in the past.

Image

I also cleaned up the plastics and metal. This was a tough job as they were all covered in gunk and crud from years past.

Image

Image

Image

Image

Interesting message written on the top of the case.

Image

This machine has definitely been in some sort of IT infrastructure role in it's life.

All cleaned, not perfect but it's the best i can do for now.

Image

Image

Image

Image

Last bit, the rear plastic panel.

Image

Image

Looking much better. Next up, tackling that PS2 port so i can actually get the machine going.
User avatar

Site Admin

Posts: 179

Joined: Sat Oct 29, 2016 2:06 pm

Post Mon Jul 17, 2017 3:10 pm

Re: Compaq Prolinea 4/25S 486 25Mhz PC Repair & Resurrection

Off with your head!

Image

All the tracks seem intact...

Image

I got out the multi meter and ran continuity tests between the points and found one section which was broken even though it looked intact. The diagram below shows where (in red.)

Image

It was between a via and a component so i bridged these with a wire.

Image

Image

PS/2 port back on...

Image

Image

Sadly, still not working...

Image

I did wonder if it was my adaptor as i have no PS/2 keyboards. I tried one from next door and that didn't work either so more digging needed. During a little time out i browsed eBay and looked to see if any boards were around for this machine. Amazingly, there were lots of them! Seems there are more boards for these machines around than actual machines.

They were around £35 but one which had just been listed was £15, I snapped it up quick because at that price... it's worth just getting a known working board and save myself the time and effort diagnosing this board further.
User avatar

Site Admin

Posts: 179

Joined: Sat Oct 29, 2016 2:06 pm

Post Thu Jul 20, 2017 11:14 am

Re: Compaq Prolinea 4/25S 486 25Mhz PC Repair & Resurrection

Ok, new board came, mixed results...

Image

Came with a CPU which was nice! A higher spec 50Mhz model.

Image

First things first was obviously remove that old battery! It was just starting to leak so caught it just in time.

Image

Image

As you can see above, these newer revision boards actually have a track for charging on the PCB so no wire to remove. I could break the track but that would be messy and I actually got a proper socket and a rechargable coin cell battery rated at 3.6V so this will be much more original and clean.

Image

Image

Image

A very tight fit but it works and looks much cleaner.

Assembling the machine..

Image

First power on...

Image

Nothing... Hmmm, I tried removing the RAM to see if the BIOS would beep and show me signs of life from the board... It didn't.

Not good!

Image

I tried swapping out the processor with my 25Mhz chip, no joy!

Image

I also tried swapping out the BIOS ROM's

Image

One of my IC's was a earlier revision than it originally had but at this stage, try anything...

Image

Nothing.. Tried it with the later revision IC and one of the same models from my other board.

Image

Still nothing... Looks like a dead board... Next step will likely be removing the battery and sticking it into the oven and hope a re-flow will kick it back into life.

Not having much luck with this machine. :(
User avatar

Site Admin

Posts: 179

Joined: Sat Oct 29, 2016 2:06 pm

Post Thu Jul 20, 2017 12:16 pm

Re: Compaq Prolinea 4/25S 486 25Mhz PC Repair & Resurrection

One last ditch effort, re-flow...

Image

Image

Sadly, still completely dead... Lost interest for now, a project for another day.

Image

Return to Computer Projects



cron