Compaq Portable I - corroded keyboard

[sid]

Hello,

I recently picked up a Compaq Portable I that's fully functional, except for the keyboard being completely non responsive. The screws on the keyboard were pretty rusty (but none on the chassis were), so it looks like the unit was exposed to a bit of moisture while in storage, and the keyboard being at the bottom took the worst of it.

I opened up the keyboard, and this is what I found:

It looks like a lot of the traces are completely corroded away in places, but I can't tell for sure if it's just surface corrosion. The foam holding the foil to the keys is deteriorated too - falls apart if I touch them.

The weird thing is that the keyboard actually works if I touch the pads directly with my finger, but it doesn't work if I stick the foil to paper and then touch it to the pad. Not sure if this is an indication of the traces being ok or not.

...

Do any of you more experienced folks have any recommendations on how to proceed? Should I try to clean off some of the corrosion with a mild abrasive and see if anything is left of the traces?

 

[modem7]

The weird thing is that the keyboard actually works if I touch the pads directly with my finger, but it doesn't work if I stick the foil to paper and then touch it to the pad. Not sure if this is an indication of the traces being ok or not.

If you enter the following into Google, you will see lots of hits.
site:www.vcfed.org Compaq Portable keyboard foam

I know from threads on these forums that some people see foil and instantly assume that the foil shorts out the contacts. In some cases, the foil is actually coated with a clear non-conductive layer. And in some keyboards, I guess that the travel length of the keystroke is such that the foil doesn't make it all the way to the pads. I do not know what the case is for the Compaq Portable I.

 

[SomeGuy]

The foam in these kinds of keyboards is always deteriorated. You can buy new foam pads on eBay: http://www.ebay.com/itm/Victor-9000...am-Pads-for-KeyTronic-Keyboards-/121266887970 but you will need to keep and re-use all of the silver disks and the clear plastic disks. And make sure the non-conductive side of the silver disks are face down.

These kinds of keys are called "capacitive" as each key acts as a capacitor rather than an electrical switch.

A little bit of corrosions on the board's metal contacts won't usually bother the operation of the keys. Just wipe the board down with isopropyl alcohol. (No need to scrape up the board trying to remove that stuff. Kind of a bonus from being capacitive) Touching the non-conductive side of one of the pads to each should show if it works.

That board doesn't look too bad to me. I'd kind of doubt the traces are eaten through. Of course, you could test them with a volt/ohm meter.

Also an extra tip: if the keys are grungy there is probably no need to remove each key top. Once the pads and disks are removed, everything on the top part is just plastic and the springs, and can be given a bath. That avoids breaking or bending the keys, that are probably attached quite tightly.

 

[sid]

If you enter the following into Google, you will see lots of hits.
site:www.vcfed.org Compaq Portable keyboard foam

I actually read through most of those threads before posting (I found them using virtually the same Google search as you suggested), but I had assumed I'd have to deal with the damaged traces before dealing with the foam. I actually expected to hear from you guys that the board was done and just go with some other solution like AT2XT.

I know from threads on these forums that some people see foil and instantly assume that the foil shorts out the contacts. In some cases, the foil is actually coated with a clear non-conductive layer.

Wait, there's supposed to be foil on the plastic? I thought people were just referring to the plastic itself as the foil. I only see clear plastic pads on mine. On a second look, I see a few of the plastic pads have bits of foil on them, but the vast majority of the keys are just clear plastic and foam. Maybe the foil rotted away from moisture exposure.In any case, that explains why touching the 'foil' to the contact pad wasn't working...

 

[sid]

That board doesn't look too bad to me. I'd kind of doubt the traces are eaten through. Of course, you could test them with a volt/ohm meter.

Well, I just tested a few of the worst looking traces, and they're actually fine - thanks! (In hindsight, I should have done this test before posting. I guess I just assumed the worst.)

So it looks like this is just a foam replacement job then..

The foam in these kinds of keyboards is always deteriorated. You can buy new foam pads on eBay: http://www.ebay.com/itm/Victor-9000...am-Pads-for-KeyTronic-Keyboards-/121266887970 but you will need to keep and re-use all of the silver disks and the clear plastic disks.

As per my previous post, the foil seems to be rotted completely away leaving only the plastic circles. Do you know offhand if some other material would work? (Like say regular tinfoil glued behind the plastic circles)

Also an extra tip: if the keys are grungy there is probably no need to remove each key top. Once the pads and disks are removed, everything on the top part is just plastic and the springs, and can be given a bath. That avoids breaking or bending the keys, that are probably attached quite tightly.

Thanks for the tip, I'll probably do this. This machine was used to run the books for a small auto shop, so the whole thing was pretty grungy. (All clean now though, except the keyboard.)

 

[RWallmow]

As per my previous post, the foil seems to be rotted completely away leaving only the plastic circles. Do you know offhand if some other material would work? (Like say regular tinfoil glued behind the plastic circles)

You can use Mylar balloons and a die punch to make new foil discs. Tinfoil would not work as it is conductive and would short the contacts, and that's not how these work, it just needs to detect some capacitance.

 

[SomeGuy]

Interesting. The ones I have seen were silver and did not look like they could separate in to different layers.

It *could* be that whatever material they used on these clear ones have sufficient capacitive quality to operate the key switch. Might just try a couple on new pads and see what happens.

 

[sid]

Update: I made an order in for replacement foam pads from the ebay seller linked above. I plan to use a mylar space blanket for the replacement foils.

In the meantime, I put together an AT2XT adapter to use with this machine for now until I get the original keyboard rebuilt.

I interfaced with the keyboard cable connector that plugs into the keyboard circuit board.

Note: The Compaq Portable I outputs 12v to the keyboard instead of the usual 5v that the AT2XT board (and the PS/2 keyboard) expects. I just added a 7805 voltage regulator to the AT2XT to compensate.

In case anyone is interested, here's the pinout:

 Female connector that plugs into the keyboard, fat side up:

 [123]
 |456|

 1: GND
 2: VCC (+12V)
 3: GND
 4: RST?
 5: DATA
 6: CLK

Some photos:

 

[MattW81]

Hello,
I'm new to the forum but since I just rebuilt the keyboard for my Compaq portable I thought I would share my solution. I ended up using applicator sponges that my wife uses for applying her make up to replace the deteriorated foam and a mylar space blanket from the sporting goods store. I also re-used all the stiff plastic discs that clip into the bottom of the keys. It was a very tedious process but worked out very well for me. As you probably know these are capacitive switches and do not rely on an actual electrical connection between the pads on the PCB. You must be sure that the conductive side of the mylar is glued to the foam. You can use the continuity tester function on a multimeter to ensure this. I first used contact cement to glue the mylar to the applicator sponge and then used a piece of copper tubing from Ace hardware to punch out the foam discs with mylar film. Then I cemented the stiff plastic discs to the other side to complete the sandwich. Then a small flat blade screwdriver was used to clip them back into the bottom of the keys. Please excuse me as I'm new to forums in general. If I knew how to post pictures I would. Aside from my scratch built z80 machine I'm really green with these types of machines and could really use some help on the software side. I hope I can meet some knowledgeable people on this forum who can help me get up to speed.

 

[sid]

Hi MattW81, welcome to the forums... I'm pretty new here myself.

I actually just finished rebuilding the original keyboard on my Compaq portable last night. I used a procedure similar to yours: reused the stiff discs, used a 7/16th leather punch on a space blanket to make new foil "contacts", and used a multimeter to ensure the conductive side of each foil contact was facing up. For foams, I just ordered some off of ebay, which came with adhesive already on both ends, so I saved a bunch of time.

The rebuilt keyboard works perfectly, though I'm missing one spring, which I left off the scroll lock key (along with the foam contact) for now until I can find a replacement. Or maybe I'll just leave it - what use is the scroll lock key anyway?

As far as posting pictures to the forum, I just upload them to imgur.com (you don't even need an account), and just link to them from here. Use advanced editing mode to embed links to pictures. You can also attach photos directly to your post in advanced mode, but the max resolution is very low.

 

[rvdbijl]

Compaq to AT (or XT) keyboard converter

Compaq to AT (or XT) keyboard converter

New to the forum, got here by doing some Google searches, and found this interesting post.. I also have a Compaq portable I'm trying to resurrect. It works fine, except for the keyboard. I've been replacing some foam pads here and there, but it always ends up causing more issues.
I really like this option -- the XT2AT converter, adapted for the Compaq. But I have a few questions --

Is this just the standard XT2AT converter with a 7805 in front of it? And are the data and clock lines running still running at 5V?

And if so, would I be able to connect an XT keyboard to the Compaq by just putting a 7805 in front of it? And directly connect the data and clk lines? (i.e. not use the XT2AT converter or any of its components?)

Update: I made an order in for replacement foam pads from the ebay seller linked above. I plan to use a mylar space blanket for the replacement foils.

In the meantime, I put together an AT2XT adapter to use with this machine for now until I get the original keyboard rebuilt.

I interfaced with the keyboard cable connector that plugs into the keyboard circuit board.

Note: The Compaq Portable I outputs 12v to the keyboard instead of the usual 5v that the AT2XT board (and the PS/2 keyboard) expects. I just added a 7805 voltage regulator to the AT2XT to compensate.

In case anyone is interested, here's the pinout:

 Female connector that plugs into the keyboard, fat side up:

 [123]
 |456|

 1: GND
 2: VCC (+12V)
 3: GND
 4: RST?
 5: DATA
 6: CLK

Some photos:

 

[rvdbijl]

Quick update -- I decided to try it (the 7805 regulator and a regular XT keyboard). The system boots up with a 301 (keyboard) fault, but the standard XT keyboard I connected to it works fine.

Awesome post! Saved me a lot of time with foam pad replacements...

 

[wafflehouse]

what would it cost to get one of these build?