Compaq Portable 486c

[CompaqSniffer]

It just arrived today, check it out:

Oh and does anyone know of a good keyboard cable replacement for this thing?

 

[Paralel]

A locking PS/2 interface? I've never seen one of those before.

 

[CompaqSniffer]

This one doesn't lock, it just has a pull tab to make it easier to get out, it's kinda plugged in at an awkward angle in the 486c. I thought it was too though at first.

 

[CompaqSniffer]

Oh and I remember asking somewhere else on the forum(not this thread), but I was looking for replacement bulbs for the backlights, but they weren't hard to find on Amazon, this is what the backlights look like, this is one of the reasons I wanted the 486c, because it has so many strange quirks.



The bottom light is catastrophically blown.

 

[mikerofone]

Ouch, I wonder how it would burn out like that? Seems like it'd be a challenge to replace. What replacement tube did you find?

 

[CompaqSniffer]

Anyone got a replacement in mind?

 

[mikerofone]

You already discovered this thread it seems, but it has pointers on fitting a new display: https://forum.vcfed.org/index.php?threads/replacing-the-screen-of-a-compaq-portable-486c.67664/

I don't have any other leads, sadly.

 

[CompaqSniffer]

yeah I literally broke it last night, the replacement bulbs I got were a little too big and when I screwed in the screen, it exerted to much pressure on the panel causing it to crack. I've been looking over that thread, and have been considering getting a new screen, but I wanted to try getting an original. If I would have seen this earlier:

Hello everyone,

Here is a quick update on the advancement of the screen replacement project. (Sorry for the terrible photos. This week-end the weather was bad, and my phone camera works poorly in low light conditions).

About the non-working system: turned out the new (old stock) screen was indeed faulty and died due to the stress of heavy use during one week. Since I cut a corner, I couldn't possible ask for a eBay refund... Anyway, I bought another one, and this time I kept it intact inside the Compaq and cut an extra corner of the frame instead. The screen is now held with 2 screws, but it is more than enough to keep it stable: the frame just fit and cannot move already, even before putting any screw.

Now, to make the electrical connection... Turns out the LCD controller board is slightly too thick to fit behind the screen. Instead, I keep it inside the computer, next to the VGA card. At first, I connect the bare minimum to carry out a VGA signal: red, green, blue, VSync, HSync and GND:
View attachment 1025397

The original inverter board provides a 12V supply with enough amperage for a screen (hopefully!!!) and I got it across this capacitor:
View attachment 1025398

Once everything in place, it is totally invisible from the screen side. On the inside, the extra board takes the room of one of the ISA socket. Not so great, but for the moment it will suffice:
View attachment 1025399View attachment 1025400

And yes, after reassembling completely, it works:
View attachment 1025401

However/Next steps:
- The image is affected by some interference. The OSD from the controller is not. So the issue is the VGA link between the graphic card and the screen controller. I plan to re-do it with proper return paths from the R, G and B channels.
- I don't like the idea of this new board showing when the computer case is open. I may desolder the bulky connectors to try to make it fit anyway. Let's hide all modern electronics!

I probably wouldn't have broken it because I could have just hooked up 12V power to some LED strips.

Anyone reading this in the future DO NOT USE NEW FLUORESCENT BULBS, you will crack the screen due to extra thickness. if you can find original size ones use that, but I'd say I took an arrow for the community. I may be down a screen, but at least we know that replacing the bulbs is not a viable option. I couldn't find originals anywhere.

Why is it that I'm stuck with repairing screens for compaqs? I'm literally working on the portable III screens as well and writing a guide for them. It's almost like Compaq should've just stuck with CRTs since the portable I and II. I'd much rather repair board traces than plasma screen ribbon cable traces. I was praying for power supply faults, but NO it just had to be the damn screens. Both my PIII and 486c are notorious for PSU faults, but both of them have flawless PSUs, the only thing that's broken are the screens.

 

[CompaqSniffer]

Ouch, I wonder how it would burn out like that? Seems like it'd be a challenge to replace. What replacement tube did you find?

Oh and these were the replacement tubes I bought, don't buy any 9in ones they're too thick