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Getting Compaq Portable 1 running

You used plumbing flux on a PCB? That stuff might have eaten right through the traces on the board. Best to clean it off ASAP and start buzzing out traces looking for damage.
 
That flux is really supposed to be used with plumbing repairs. Read the questions/comments:

We would not recommend this product for electronics. We would recommend using our Rosin Core Wire Solder for electronic applications.
 
I bought it from a local hardware store and happened to find its listing on Amazon just now when I looked for it. The package didn't say anything about not putting it on electronics.

All right, then how do I get it off? With acetone?
 
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I would say no. I'd be worried it might damage your circuit board even more. Since I have never had to clean a board I will let the experts tell you how to properly clean it.
 
That is a plumbing flux. Not what you want to use for electronics. Some plumbing flux are corrosive. I didn't find any particular information on cleaning it off but it says its petroleum based. I would use a cleaner you have that works on oil/grease. I have used a citrus cleaner de-solv-it on solder paste flux my normal cleaners didn't remove well. It also seems to work well on oil/grease. I then need to remove it with a normal household spray cleaner. May take a couple repeats to get fully clean. I use an old toothbrush to scrub with. I use faucet hot water. I never have tried hotter. Boards are fine with water as long as they don't have components like pots which water can get stuck in. I use an air compressor to blow the water off but board will be fine shaken and blotted then air dried preferably with moving air until fully dry.

Get some proper flux cored solder and flux. Separate flux isn't a hard requirement but can help with older electronics which may have more corrosion on the leads.
I mainly have been using MG chemicals 4885WS solder and chipquik CQ4LF-1.0 flux which are water clean. Looks like they discontinued the solder so I'll be picking another.
Rosin core solder is classic but will require the alcohol that your previous cleaning instructions recommended. Its more effort to really get clean.
 
All right, I used orange spray Goo Gone. After I let that sit for about 5 minutes, I scrubbed with the soft toothbrush, then rinsed it with isopropyl alcohol, then scrubbed again. Then I rinsed with water. Then I set it on the heat vent so the furnace air would gently warm-air-dry it. The board now appears clean.

I threw out the plumbing flux. Good riddance. 🗑

I then inspected the solder joints on the new-used chip. Two of them had fractured on the rear side of the board, apparently either by being moved before they were solid or by not having enough solder. I resoldered them, plugged in the VDU board, turned on the computer, and the built-in monitor now appears normal. Hallelujah!!

Now on to replacing the keypads. ⌨️
 
I've still been trying to determine how to best remove the bad microchip from the VDU board. I thought it would be a piece of cake: melt the solder surrounding the legs and take the chip out. The problems I have encountered so far have been:
  1. All legs have to have liquid solder simultaneously. That is easy to make happen with a soldering iron on a resistor. That is impossible to make happen with a soldering iron on a 20-leg microchip.
  2. Another option for having the solder be liquid is a heat gun. But since I am not skilled with a heat gun and I think me using one would be dangerous, that is not a path.
  3. I tried using copper solder wick. After working for a couple hours getting the solder wicked from the bottom of the board, the chip will still not lift off. I can't see any more solder that is holding it on, but apparently I am wrong. I can't just yank it off despite solder still being there or I risk destroying the traces on the board.
  4. Another option is to cut each of the individual microchip legs and then the body of the microchip will be free. Then I would just unsolder each loose leg. The problem with this method is that the microchip is so close to a neighboring microchip that I have yet to find an instrument that can reach in and snip the individual legs. What I really need is needlenose pliers, except the nose has to be bladed for cutting, not knurled for gripping. I just bought a set of small cutting pliers, but they still won't get in there. This was the smallest tool I could find after going to 2 hardware stores.
Here is a picture with a ruler for scale. Can anyone please give a hyperlink for buying a tool for this work on Amazon or anywhere else?
Cutting the chip off and removing the legs one at a time, as you did. Well done.

Another solution is simple but not cheap. Add some solder to mix new solder with the old solder, to lower the melting point. Then, use this:


It's expensive, but it's the best $300 I've ever spent.
 
Hey folks! While I didn't follow the thread very closely yet, I want to thank you for your research here.

This is the first and only pictures of a working Assy 0000007 VDU I've found., and jumper settings from yours are exactly what I needed to get my working with my external display.

Thank you folks, and congrats on your work, @Bill-kun
 

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Hey folks! While I didn't follow the thread very closely yet, I want to thank you for your research here.

This is the first and only pictures of a working Assy 0000007 VDU I've found., and jumper settings from yours are exactly what I needed to get my working with my external display.
And that is why forums are the best online form for these discussions. If the logic, explanations, steps, and pictures are well-documented in a forum like this, they can stand forever and be found by search engines and used again when someone else needs that same incredibly obscure information years later. 👍

And I didn't realize that I didn't give another post to say that, now months ago, the keypads from Texelec came in, it took an evening to put them in, and every key works fine now!

I added a CF card adaptor expansion board, and a 256 MB. CF card as a virtual HDD, and the Compaq 1 is fully operational and in a closet for the time being, since I've moved on to fixing other vintage computer units. Total success!
 
I too got the pads from texelec. They worked like a dream. I have haven't been able to boot from the xtide sd i also got from them yet. I'm just assuming I'm not creating a bootable disc image properly.

Some new old stock floppies and a gotek are in the mail.
 
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