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tkc8800
August 26th, 2014, 09:04 PM
I saw this Compaq portable advertised in my local area, not knowing much about these machines I did a bit of research on it. I discovered that it was not only the first IBM pc clone but also Compaq's first product from the early 80's. I really like these old "portables" with built in CRT's so I snapped it up. The price was fairly cheap, so I bought it without doing much testing. The seller didn't have any working boot disks, so I just tested that it powered up and displayed a missing boot disk prompt on the screen, that was good enough for what I paid.

On getting it home and doing some initial testing, I was happy to get it to boot from the A drive with a DOS 3.3 boot disk, but on the down side, I couldn't get any of the keys on the keyboard to respond. No really being able to do much more at that stage I pulled it apart and and gave it a full clean out. On pulling apart the keyboard I discovered that is uses these capacitive key pads under the keys to make contact with the circuit board. I've never seen these before, but did a bit of reading and found out they are used on several other models like the Sol20 and Apple Lisa. It was pretty clear to see why none of the keys were working as both the sponge material and the Mylar on the key pads had totally perished (see photo below). I read a great guide on a Sol 20 website that suggested making your own pads using sponge discs topped with aluminum foil and clear plastic tape. I didn't have any sponge material on hand so I just used some padded double sided tape instead. I create a test key and tested it on the keyboard pcb and all keys worked. I then proceeded to make similar pads for all keys on the keyboard. This took a couple of hours but once re-assembled, I had a fully working keyboard. The keyboard fix was good as I can now use the machine, but I'm not happy with the feel of the keys. The double sided tape that I used does have some spring to it, but it's way too hard compared to the sponge material. So at some stage I'll redo the pads using a more appropriate material.

With a working keyboard I did some further testing on the machine and found that the B drive didn't read any disks. I pulled it out and cleaned it internally and also did a thorough head clean, on re-installing the B drive it now reads some disks, but it's not perfect. I've noticed it gets to a certain track on the disk and then comes up with read errors. I'll need to extract that drive again and check the rails for debris. I can launch some programs from that drive now so it's better than before. Everything else on the machine seems to work well, the display is good, there's some geometry issues, but the green screen display is very sharp and there's no sign of any burn in. The machine has the floppy printer card installed and also has an AST SixPakPlus clock/memory/serial upgrade card installed. Memory reports at 640k, I also replaced the 3v battery on the AST card and I found the AST clock utilities on web, the clock now saves the date and time.

After a thorough clean the case came up really well, no cracks or visible damage, so cosmetically it's really nice.

If anyone out there has the original disk images for the Compaq DOS v1 or v2, or any other resources or manuals for this machine, I would love to get a copy of those.


Case prior to cleaning:
http://tkc8800.com/images/compaq_portable/cp1.JPG

http://tkc8800.com/images/compaq_portable/cp2.JPG

The perished capacitive key pads:
http://tkc8800.com/images/compaq_portable/cp4.JPG

Testing the keyboard with the pcb:
http://tkc8800.com/images/compaq_portable/cp5.JPG

Here's what was left of the keypad foam:
http://tkc8800.com/images/compaq_portable/cp6.JPG

My home made capacitive key pads:
http://tkc8800.com/images/compaq_portable/cp7.0.JPG

Working keyboard:
http://tkc8800.com/images/compaq_portable/cp7.1.JPG

Top view with cards removed:
http://tkc8800.com/images/compaq_portable/cp8.JPG

Working machine after clean out and keyboard fix:
http://tkc8800.com/images/compaq_portable/cp9.JPG

http://tkc8800.com/images/compaq_portable/cp10.JPG

The floppy/printer board:
http://tkc8800.com/images/compaq_portable/IMG_1461.JPG

The full size video board:
http://tkc8800.com/images/compaq_portable/IMG_1462.JPG

The AST SixPakPlus
http://tkc8800.com/images/compaq_portable/IMG_1463.JPG

reenigne
August 27th, 2014, 11:45 AM
That video card is fascinating - I had no idea there was such a thing as a hybrid CGA/MDA card with composite output. Nice teardown - thanks!

Al Hartman
August 27th, 2014, 11:50 AM
I saw images of Compaq MS-DOS disks on www.vetusware.com

tkc8800
August 27th, 2014, 06:52 PM
That video card is fascinating - I had no idea there was such a thing as a hybrid CGA/MDA card with composite output. Nice teardown - thanks!

Yeah, the video card is impressive, it's a massive thing. Pretty well thought out, there's an internal cable that connects to the top for the in-built mono screen.

k2x4b524[
August 27th, 2014, 07:11 PM
I don't think that is MDA, i believe it is some kind of modified CGA with a special tube, that will emulate colors in different shades of green. I might be wrong, a second opinion?

motley2659
August 27th, 2014, 07:31 PM
Ugh @ foam and foil key switches. Such a great looking computer with such a mushy keyboard.

tkc8800
August 27th, 2014, 07:54 PM
Ugh @ foam and foil key switches. Such a great looking computer with such a mushy keyboard.

I'm not happy with it either, it's a temporary fix, it beats no keyboard. As soon as I can source some appropriate replacement foam pads, I'll re-do it. The fix I did is fully reversible so no problems there.

tkc8800
August 27th, 2014, 08:04 PM
I saw images of Compaq MS-DOS disks on www.vetusware.com

Thanks, I had a look, they have some later versions dated 1988 but they also have v1.25. Also some early Compaq Basic downloads. I can't download them because their daily limits are harsh, I'll try tomorrow. Also found some other early versions v1.1, v2.12 on Winworld here:

http://wdl2.winworldpc.com/Abandonware%20Operating%20Systems/PC/DOS/Microsoft/

reenigne
August 27th, 2014, 11:00 PM
I don't think that is MDA, i believe it is some kind of modified CGA with a special tube, that will emulate colors in different shades of green. I might be wrong, a second opinion?

The pictures definitely look like MDA, and wikipedia (http://en.wikipedia.org/wiki/Compaq_Portable) says "The machine used a unique hybrid of the IBM MDA and CGA which supported the latter's graphics modes, but contained both cards' text fonts in ROM."

motley2659
August 28th, 2014, 02:48 AM
The IBM Portable 5155 is CGA but run through a composite amber display, like a mini Amdek 300A. I may be wrong, but the Compaq looks like a green phosphor version of that.

SkydivinGirl
August 28th, 2014, 05:37 AM
A very nice restoration! Well done. :)

Heather

sergey
September 4th, 2014, 02:36 PM
Great job!
I also have a Compaq Portable. And just as in your case the keyboard pads deteriorated. So I need to find time and materials to fix the keyboard.
I tried using double sided adhesive tape + aluminum foil + transparent scotch tape, but it doesn't work as good as original foam pads. So I am still looking for a better solution.

lee4hmz
February 9th, 2015, 10:31 AM
The pictures definitely look like MDA, and wikipedia (http://en.wikipedia.org/wiki/Compaq_Portable) says "The machine used a unique hybrid of the IBM MDA and CGA which supported the latter's graphics modes, but contained both cards' text fonts in ROM."

I went looking for an official Compaq manual, and I found one on minuszerodegrees. It says that the hi-res text mode is indeed 720x350 (which is good, because I thought it was 640x400 myself).

PhilipA
February 13th, 2015, 05:56 AM
Great job!
I also have a Compaq Portable. And just as in your case the keyboard pads deteriorated. So I need to find time and materials to fix the keyboard.
I tried using double sided adhesive tape + aluminum foil + transparent scotch tape, but it doesn't work as good as original foam pads. So I am still looking for a better solution.

Mylar emergency blanket from on outdoor sports store (think Academy sports), I used contact adhesive on a thick high-density foam sheet I bought at a craft store. Applied the adhesive, made sure with a meter the conductive side of the Mylar was being glued, then punched out with a home-made punch (sharpened pipe) and stuck to the original plastic backing circles that were still stuck in the keys.

--Phil

gnelec
March 19th, 2015, 02:51 PM
I don't know weather you guys can direct me to the right forum but I have a Compaq SLT/286 Portable with expansion base! Rare I know! Ive installed 2 ISA cards to the base, a future domain SCSI card & a SoundBlaster 16 card & for some uknown reason the system wont detect them. Ive tried playing around with the I/O, IRQ, DMA etc still no joy. its like the SLT thinks that the ISA bus doesn't exist. Have any of you guys had any issues with this? or know where to get info on how to set up the expansion base properly & ISA setups?