PDA

View Full Version : Got a Compaq Portable coming...



alank2
April 24th, 2017, 05:43 AM
Hi Everyone,

A guy on eBay has some of them that look clean, but don't have a working CRT. I plan to tear it down and try to figure it out when it arrives. It only has a pair of 5.25" floppies and it has been forever since I had any. It will come with a 2.11 dos diskette so at least I have something to try to boot.

Over the long haul I'd like to get the CRT working and perhaps install one of those XT IDE cards I've seen with some CF in it for a hard drive.

Thanks,

Alan

Theoisle
April 25th, 2017, 03:59 PM
I have a Compaq Portable Plus that cam with a 360kb floppy and a bad MFM HD. I have no installed the Lo-Tech XT-CF card and the Kiselev Floppy Disk controller. I can now boot to any CF I put in there and I added a 1.44MB floppy where the HD was using the HD base plate as a mount and cut a hole in the HD cover plate to access that floppy. Without the FDC I could not access the floppy. Copy the XT-IDE Universal ROM to the end of the FDC ROM and loaded both of them to the EPROM on the XT-CF card. I had configured the FDC ROM for A as 360 kb and B as 1.44MB just be sure to adjust the checksum as needed. This is all located at the end of the FDC ROM. Read the info on the FDC ROM and it is all there. The bottom line is that without the FDC, I could only access the 3.5" floppy as 720 kb with the original floppy controller. Installing the new FDC now allows me to access the 3.5" floppy as 1.44MB. The FDC needs the jumpers set to point to the area the XT-CF loads the ROM.

BTW, there is an external composite video jack on the video card, so you should be able to use it until you fix the CRT.

alank2
April 26th, 2017, 01:05 PM
Hi,

It is arriving tomorrow, so I'll see what type of shape it is in. I've got a couple of monitors that can display composite so we'll see if I can get it going that far!

Thanks,

Alan

compu_85
April 28th, 2017, 08:25 AM
Plan on having to repair the keyboard. Do research on the KeyTronic foam & foil switch.

There's a vendor on ebay who sells replacement foams. I got a set, they work really well, and are worth his asking price since you don't have the frustration of making ones yourself. You can easily make replacement "contacts" using foil wrapping paper and a leather punch.

Here's the set of replacement foams I got: http://www.ebay.com/itm/Victor-9000-SIRIUS-1-Keyboard-repair-Foam-Pads-for-KeyTronic-Keyboards-/121266887970 I have no affiliation with this seller.

You might also want to replace all the tantalum capacitors on the motherboard and controller cards. They like to short out and either explode, or trip the overcurrent detection on the PSU. When I got my Portable 1 was blown up, 2 were shorted, and another shorted after the system had run for a few hours.

-J

alank2
April 28th, 2017, 09:31 AM
Hi,

You are right on all counts!!! I replaced two shorted tantalum's, one on the main board and one on the video card. Both on the +12V rail. There are others - do you think the ones on the 5V will also fail?

I ordered some new foams to fix the keyboard as well.

Thanks,

Alan

compu_85
April 28th, 2017, 11:29 AM
On my Compaq I only replaced the caps that shorted. It's been fine for a year. I'm sure if I went to take it to a festival another would fail though...

I'd also suggest you redo all the key foams. Playing whack a mole with KeyTronic foams is a PITA. The foams can seem fine now, but once you start using them they'll degrade quickly. I've had to redo my Lisa keyboard 4 times... the last time I used the foams from the German vendor and hope to never need to do it again!!!

-J

rorypoole
April 28th, 2017, 07:06 PM
Hi, I have also just got a Compaq portable, it's the first model with the full hight 5.25 inch disk drives and 8088 cpu, at the moment its not working, and has a hole in graphics card from where a tantalum capacitor exploded! I have found a replacement, but would like to replace all the tantalum and electrolytic capacitors with ceramic as you can get them in high values now, any one know where I can get scmatics? Thanks

rorypoole
April 28th, 2017, 07:12 PM
Can anyone​ help me I also need some used double density 5.25 360k disks with DOS 5 and maybe a game like Tetris to get me started, I have found an image of 360k version of DOS 5 https://winworldpc.com/product/ms-dos/50
My address is in the UK. Thanks

alank2
April 28th, 2017, 07:41 PM
I got pretty far with it tonight. I did have something fizzle and smoke a bit - tracing that down to the little power box "sprague filter". It is a sealed metal box, but it kept working after the fizzle event.

This and the video card graphics hole that rorypoole mentions makes me a bit nervous for the rest of the tantalum's though! Do you guys think it is only the ones on the 12V (15V spec'd) that were most likely to have trouble? The power supply board has tantalums and there are a few more on the main board though I think they may all be 5V.

A friend of mine found a 3.30 dos boot disk and I was indeed able to boot something finally! I formatted some of my new disks with a system and began my plan of recreating the compaq diagnotics and compaq 3.31 dos disks. One snag is that with only two floppy disks, you can't very well transfer over a file that is the size of a disk image! It won't fit!!! I thought I had a plan to handle this with my own custom disk imaging tool that has compressoin, but it ran into trouble. Probably some of the bios calls I was using were not implemented in this compaq bios. I ended up writing a very simple utility that just wrote sectors only to drive B: and split the disk images into two files, a first half and a second half. The tool then stops after reading the first half from a disk in drive A: and allows me to swap the disk to a second disk with the second half. While a bit cumbersome, it did allow me to create the disks I needed. I ran the diagnostics and it passed all of them!

rorypoole
April 28th, 2017, 09:42 PM
One programme that I used when in college was interlink, it is free with DOS 6.2 and links the 2 computers with the serial or printer port, if using the serial port the programme can copy it's self over, only a null modem lead needed, the Compaq can be running DOS 3.3 and have it's drives mounted on a more modern pc, in the past I had the drives usable from Windows 95/98 hard drives can also be shared http://www.pcxt-micro.com/dos-interlink.html
Great programme, the needed leads can be easily built or found on eBay. Hope this helps

modem7
April 28th, 2017, 11:14 PM
Do you guys think it is only the ones on the 12V (15V spec'd) that were most likely to have trouble?
In the IBM 51xx series of computers, the tantalums that IBM use on the motherboards and cards to filter the 12V and 5V rails, are all 10F/16V.
At [here (http://minuszerodegrees.net/vcf_motherboard_failure_history.htm)] is a 10-year history of 51xx motherboard failure that people recorded here on these forums.
Only one failure of a tantalum on a 5V rail; the remainder are on 12V rails.

So, on the subject IBM motherboards and cards, it may be that the probability of failure is greater for the tantalums on the 12V rails because 12V is a lot closer to the tantalum's 16V rating than 5V.

Note too that time and time again, I observe that the likelihood of failure is greater if the tantalum has been unpowered for years. I run my 51xx computers at least once a year (for a few hours) and no problem. But when I acquired those computers many years ago, they had their share of faulty tantalums.

alank2
April 29th, 2017, 06:50 AM
In the IBM 51xx series of computers, the tantalums that IBM use on the motherboards and cards to filter the 12V and 5V rails, are all 10F/16V.
So, on the subject IBM motherboards and cards, it may be that the probability of failure is greater for the tantalums on the 12V rails because 12V is a lot closer to the tantalum's 16V rating than 5V.


This is what I was wondering. They didn't derate them enough and probably should have used something more like 25V tant caps. I had it running for a couple of hours last night, so far so good, no more failures.

modem7
April 29th, 2017, 04:52 PM
They didn't derate them enough and probably should have used something more like 25V tant caps.
The capacitors are 30 years old, and so that is a possible factor in the behaviour.


I had it running for a couple of hours last night, so far so good, no more failures.
Do a few power cycles as well.

rorypoole
May 7th, 2017, 04:06 AM
I am researching 10uf leaded ceramic capacitors that will be a direct replacement for the tantalum's, but if used regularly the tantalum's should be ok.

rorypoole
May 7th, 2017, 04:15 AM
Hi alank2, what games do you plan to play on your Compaq, the vdu card can be connected to a us NTSC TV and some games can do very clever tricks to get more colours, and better colours look up composite artifact colors demo at https://www.google.co.uk/url?sa=t&source=web&rct=j&url=https://m.youtube.com/watch%3Fv%3DhNRO7lno_DM&ved=0ahUKEwio7o7k4N3TAhXFIsAKHWXRBqEQo7QBCB4wAQ&usg=AFQjCNF4_OOWckiwtEyr2LCWmLFJnhuK5Q&sig2=L0H0Kj3EpePzYeHhpu65nQ

alank2
May 7th, 2017, 04:48 AM
Hi Rory,

I tried hooking up a composite NTSC to it, but it was not color, and it looked like a black and white attempt at color using grayscale pixels. I haven't looked at the jumpers on the video card yet though.

I remember playing Space Quest and Ultima 5 I think when I was younger, but I'm not sure if those will play well on it or not, haven't tried yet!

Thanks!

Alan

Scali
May 7th, 2017, 04:59 AM
I tried hooking up a composite NTSC to it, but it was not color, and it looked like a black and white attempt at color using grayscale pixels. I haven't looked at the jumpers on the video card yet though.

The video card should be capable of colour with composite.
Here is a capture of a Compaq Portable with 8088 MPH:

https://youtu.be/1WQKOBRkyVs

The NTSC signal is speed-sensitive though. The NTSC clock is taken from the motherboard. On a real IBM 5150/5155/5160 motherboard, there is an adjustable capacitor to fine-tune the clockspeed, so that you can get the NTSC signal working properly. Perhaps the Compaq has this as well, and needs some adjustment.
Or perhaps the NTSC monitor/TV you used was very sensitive to speed, and you could try another with better luck.

alank2
May 7th, 2017, 05:21 AM
You might be right about this - it did look like the signal was just not quite right.

rorypoole
May 17th, 2017, 05:14 PM
I have got the new Compaq vdu/graphics card, and the 10uf 15v tantalum capacitor that exploded on the first card is very close to a power resistor, and the heat probably did not help it age well lol, there are only has 6 tantalum capacitors on this board so I will replace them all with ceramic capacitors rated for 25v or higher, I don't know if any of the 15v capacitors are on the 12v or 5v line, but 2v head room is way to close, I don't want another vdu/graphics card going up. This question may seem silly but how do you add a picture, I can upload them to the forum ok, but how do I add one to this post? Thanks