• Please review our updated Terms and Rules here

Latest score: Compaq Portable 486c

norm8332

Experienced Member
Joined
Apr 3, 2017
Messages
100
Location
USA
Just thought I'd share my latest score: The seemingly rare Compaq 486C.

My brother donated this PC, he rescued it from the trash at his work for me. Thanks bro!

It did now work when I received it. I turned it on and nothing happened. I did however notice a capacitor failure smell. I guessed it would be the power supply at this point. Sure enough after disassembly of the power supply, 4 leaky caps were found. None of them were bulging, but all of them were the same brand and value. Replaced them with new caps.

Now when turned on it appeared to be booting but the LCD was just white with some horizontal lines. I thought: Great a portable that can't be portable because the LCD is fried. I figured at this point I would be junking it but I had to at least make an attempt to find the issue. So, I carefully removed the LCD panel and disassembled it. To my amazement every single surface mount electrolytic capacitor (10 or so) on the boards in the LCD had leaked and 2 through hole caps on one of the mini boards that was attached to one of the boards. I replaced all of them. Easy to remove them by just twisting them off - Check Youtube. I only slightly pulled 1 pad and was able to epoxy it down. Epoxy stands up to the heat when soldered and the fix worked great.

Re-assembled, turned on and it worked! The screen was clear and crisp like it was new!

I just wanted to post my experience regarding the LCD panel so people know that it is easily fixable since I couldn't find anything online about it. This maybe why there are so few of these left in the wild and If this experience helps anyone it's all good.

In the end I upgraded the memory from 8mb to 24mb and the processor from 33mhz to 100mhz with an overdrive processor I had. I also added an internal sound card and The sound comes through the internal speaker because there was an existing input for just such a thing. Plus a 2GB hard drive was installed, upgrading from 200MB. This thing works great and was a fun restore.

P1010734.jpg
P1010733.jpg
 
Last edited:
Great story, I love hearing about this sort of thing, and fantastic that the only issue were the caps. Every time something doesn't work for me from now on I'll check the caps first thing.

Got to say, its a bit of an ugly thing in my opinion, but I'm jealous, as I would love to find or have unique items such as this given to me.
 
You lucky dog! I remember tearing one apart back in 1998 because I wanted to use its lcd screen for a project I was working on. (how I wish I kept that machine)
Want to trade for a portable III with a perfect working Gas plasma display??? Just kidding, you hold on to that thing, they are hard to come by. Nice score.

Do those curley keyboard wires suffer from the same ROT as the portable III cables?
 
Great story, I love hearing about this sort of thing, and fantastic that the only issue were the caps. Every time something doesn't work for me from now on I'll check the caps first thing.

Got to say, its a bit of an ugly thing in my opinion, but I'm jealous, as I would love to find or have unique items such as this given to me.

Yeah, It's the caps bad most of the time in just about anything I have found. I have a stock of them now for just such an occasion.
 
Last edited:
You lucky dog! I remember tearing one apart back in 1998 because I wanted to use its lcd screen for a project I was working on. (how I wish I kept that machine)
Want to trade for a portable III with a perfect working Gas plasma display??? Just kidding, you hold on to that thing, they are hard to come by. Nice score.

Do those curley keyboard wires suffer from the same ROT as the portable III cables?


Thanks, yeah the keyboard cable is very soft, you could dig your fingernail into it. I'm just being extra careful with it. I loaded it with a bunch of games from the era, (early 90's) and windows 95 for a NIC I added mainly to transfer files. And a boot menu etc. because I prefer IBM DOS 7.0 over 95 DOS because it is very memory efficient.

It's a fun little dos box to add to my collection.:)
 
Cool looking machine there, man. Also, it's amazing that LCDs back in the 1990's used capacitors. Beautiful display. Is it TFT or the other LCD type?
 
It looks like a tft. It has very sharp saturated color, good contrast and a decent viewing angle for the time ('91) that DSTN lacks. This was a apparently an over $7,000 machine when new.

I didn't expect the LCD panel would contain capacitors either, but it is like an inch thick in it's bare form so I disassembled it. It actually uses two 1/2 inch diameter florescent tubes for the back light!

It actually has a Wikipedia entry...well not exactly.. This machine was a 486-33 (66?), Color TFT LCD, 8MB ram before upgrades and dated 1991. This is a 486C, C for color i guess.

https://en.wikipedia.org/wiki/Compaq_Portable_486
 
Last edited:
Very nice! Definitely need to find me one of these someday. I’m a huge Compaq fan (as If that’s not obvious by my username).

You have confirmed my suspicion about leaky caps being the cause of the very common “white LCD” problem on these.
 
Very nice! Definitely need to find me one of these someday. I’m a huge Compaq fan (as If that’s not obvious by my username).

You have confirmed my suspicion about leaky caps being the cause of the very common “white LCD” problem on these.

I realize the machine is 26-27 years old but I have a 47 year old Sony stereo and many vintage computers in their 30s that all the caps were fine in. It may be a issue with the caps or the LCD design IMO that causes them to fail sooner than other vintage equipment. All the caps were leakers, no sign of pressure problems or bulging. They appear to short when finally dried out, dragging down the power rail supplied by the video card. A transistor on the video card got so hot it started desoldering itself, but I tested it and it's fine. I replaced them with 1 step higher voltage across the board.

I use all my machines periodically to ensure I'm keeping the alu oxide up in the caps. As many of you know caps need to be used once in awhile to be kept healthy.
 
Last edited:
I use all my machines periodically to ensure I'm keeping the alu oxide up in the caps. As many of you know caps need to be used once in awhile to be kept healthy.

I did not know about this. How often is once in a while? monthly, quarterly, yearly?
 
[...]

Now when turned on it appeared to be booting but the LCD was just white with some horizontal lines. I thought: Great a portable that can't be portable because the LCD is fried. I figured at this point I would be junking it but I had to at least make an attempt to find the issue. So, I carefully removed the LCD panel and disassembled it. To my amazement every single surface mount electrolytic capacitor (10 or so) on the boards in the LCD had leaked and 2 through hole caps on one of the mini boards that was attached to one of the boards. I replaced all of them. Easy to remove them by just twisting them off - Check Youtube. I only slightly pulled 1 pad and was able to epoxy it down. Epoxy stands up to the heat when soldered and the fix worked great.

Re-assembled, turned on and it worked! The screen was clear and crisp like it was new!

I just wanted to post my experience regarding the LCD panel so people know that it is easily fixable since I couldn't find anything online about it. This maybe why there are so few of these left in the wild and If this experience helps anyone it's all good.

[...]

Hi norm8332,

I recently picked up a 486c/66 whose screen was all white when turning on. Thank you so much for describing your fix, as your post allowed me to save my screen. :) The post motivated me to dig into the LCD assembly and check the caps! Sure enough, every cap on the input driver board (the one the flat ribbon cable from the machine connects to) had either leaked (the four SMD ones), or measured as open circuit on my capacitor tester (the two through-hole caps on the tiny daughterboard).
Edit: I've taken some before pictures here, in case anyone might find them useful in the future: https://photos.app.goo.gl/DvikEjfSTqjqTJiB7

I've replaced them and now have a working screen! It still shows some ghosting if there are some high contrast changes on the same horizontal line, which I assume is due to me not replacing the caps on the other board in the panel. I ran out of replacement caps, and also the caps are too close to each other for me to think that I'll be able to replace them without ruining everything. The screen now looks pretty nice and I'm looking forward to play some games on it. :)

I got lucky and the previous owner not only upgraded the computer to 28MB total RAM, but also replaced the 486 CPU with an AMD "Am5x86-P75 / Am486DX5-133W16BGC". :) I'm still shopping around for a soundcard. Seems like SB16 / Vibra cards can be had for quite cheap, so it'll likely be one of these in the end.

Again, thanks for posting, and saving my screen! :D

Cheers
mikerofone
 
Last edited:
Edit: I've taken some before pictures here, in case anyone might find them useful in the future: https://photos.app.goo.gl/DvikEjfSTqjqTJiB7

Thanks for the pictures. They are very helpful. I have been struggling with my own 486c for a while. My problem is that I can not adjust the brightness of the screen at all. I had been concentrating on the little board with the speaker on it but I may have to actually venture out and open up the whole display panel. Did you replace any of the tiny SMD capacitors?

It still shows some ghosting if there are some high contrast changes on the same horizontal line, which I assume is due to me not replacing the caps on the other board in the panel. I ran out of replacement caps, and also the caps are too close to each other for me to think that I'll be able to replace them without ruining everything.

I am seeing some of this as well which I had attributed to failing caps but given how minimal it is I was willing to ignore it. If I end up opening up the panel itself I may then have to replace those as well as I don't want to reopen this machine again (the plastic is already very brittle)

I got lucky ... replaced the 486 CPU with an AMD "Am5x86-P75 / Am486DX5-133W16BGC". :)

Interesting. I tried upgrading mine with a working AMD Power Stacker 486 to 133 MHz 5X86 (i.e. works in other motherboards) and the system refused to boot. I have an Intel 486DX4-100 OD chip in there and it has been quite happy with that. I am wondering if the BIOS in the 486c/66 is different then the one in the original model and allows for the AMD chips to work. Can you tell me what the ESU identifies your CPU as please? TIA!
 
Back
Top