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Thread: Compaq Deskpro (original 8086)_questions.

  1. #1
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    Default Compaq Deskpro (original 8086)_questions.

    Last fall I picked up an original Deskpro at a local computer recycling center, the system unit only. They warned me they thought some of the capacitors had blown in the power supply, but I planned to drop a working p/s from a spare Deskpro 286. Then I left it in the closet for a long time.

    Finally got it out today, and surprise, nothing happened when I plugged it in and hit the power switch. I had planned to plug in my Compaq dual-scan mono monitor but I discovered the silly thing didn't have a video card!

    I needed to take the cover off to replace the p/s, so here goes...

    This puppy has a 20Mb Hard Card (the actual brand) in it, as well as an AST Six-Pack Plus card. The memory looks to be fully populated: 384K ram, but no coin battery installed. I guess that's a good thing. There's also an 8087 co-processor. There's two banks of 64K ram chips soldered onto the motherboard, and two more socketed banks with 256K chips. If I read the DIP switches correctly, it's already configured for the co-processor, 640K of ram, and a RGB/EGA video card. No idea how the ram on the Six Pack is set up. I've read that the Deskpro floppy/parallel controller has a real time clock on it, but I can't find anything that looks like a battery on it.

    My problem is that my apartment is a mess right now, and I have no idea where my spare ISA video cards are. I have one of each; a clone CGA, Herc card, and an EGA card. Below are some of the components.
    SixPack.jpghardcard.jpgcpu.jpgdipswitch.jpg

    Since I'm going to ask some silly questions, I'll start with this one: I'm assuming that the Deskpro will take the Deskpro 286 power supply. They both have the same odd Compaq connector. Is this a reasonable assumption?

    Is the red dip switch package the one the motherboard uses for configuration? Never dove into the innards of an original Deskpro before. It looks like that the configuration switch box. Also, while my other video cards are buried somewhere right now, I do have two spare Compaq Portable VDU cards. No idea if they still work, and I can't put the case lid back on with that sucker in there (it's bloody high) but it should work as a standard CGA adapter, yes? Just for debugging purposes to see what's still working on this thing?

    If you look at the photos the interior looks very clean; no dust bunnies. Don't know if the recycle center cleaned the inside & pulled the video card or not.

    Anyone have anything to suggest before I drop in the p/s & VDU and see what happens?

  2. #2
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    Very nice system. If it were me, I'd probably sanity test the power connector with a volt/ohm meter to make sure things more or less match up, although it sounds like it should work.

    You might need to adjust the switch block before it might accept some video cards. I don't know specifically what each switch does on this machine.

    It is my understanding that the early deskpro systems actually supported the Portable CGA card (I guess there must have been a lower profile version?), which give a higher resolution text mode but requires a special monitor. So if it works TOO well, and tries to use that mode, you might not get any usable external video output.

  3. #3
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    Quote Originally Posted by SomeGuy View Post
    Very nice system. If it were me, I'd probably sanity test the power connector with a volt/ohm meter to make sure things more or less match up, although it sounds like it should work.

    You might need to adjust the switch block before it might accept some video cards. I don't know specifically what each switch does on this machine.

    It is my understanding that the early deskpro systems actually supported the Portable CGA card (I guess there must have been a lower profile version?), which give a higher resolution text mode but requires a special monitor. So if it works TOO well, and tries to use that mode, you might not get any usable external video output.
    I tried powering it up last night with just the video card to start. Heard a small "pop" and saw a teeny bit of smoke. A capacitor blew. Not a big explosion, but there ya go. It was marked C2, right next to the power supply connector. Alas, I no longer have any tools like a soldering iron or multi-meter any more.

    I thought about using my Compaq dual-mode mono monitor that way, but decided to go with a CGA monitor to start with. But as I said above, a capacitor blew, so we shall rest unknowing for now. I'll probably plug the cards & floppy drives into another system to see if they they work.

  4. #4
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    Let me guess, a tantalum capacitor off the -12 or +12 line. Those things love to go boom.

    Just cut it off and try again. Those are there for stability purposes and will run without, although they should be replaced eventually.

  5. #5
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    Quote Originally Posted by SomeGuy View Post
    Let me guess, a tantalum capacitor off the -12 or +12 line. Those things love to go boom.

    Just cut it off and try again. Those are there for stability purposes and will run without, although they should be replaced eventually.
    I'll give that a try and let you know what happens. It would be nice to get this puppy running, but even if all I can salvage are the 2 floppy drives, the Six Pack card, and the Hard Card should make it worth the price.

  6. #6

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    Quote Originally Posted by SomeGuy View Post
    It is my understanding that the early deskpro systems actually supported the Portable CGA card (I guess there must have been a lower profile version?), which give a higher resolution text mode but requires a special monitor. So if it works TOO well, and tries to use that mode, you might not get any usable external video output.
    Yes - there are five iterations of the Portable CGA card, and all but the first will also fit in a Deskpro. They have jumpers on them to control whether the 9-pin video socket is enabled in high-resolution modes (as it would be on a Deskpro) or disabled (as it would be on a Portable). The Deskpro motherboard switch SW6 controls whether the BIOS uses standard CGA timings (off) or high-resolution (on).

  7. #7
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    Quote Originally Posted by SomeGuy View Post
    Let me guess, a tantalum capacitor off the -12 or +12 line. Those things love to go boom.

    Just cut it off and try again. Those are there for stability purposes and will run without, although they should be replaced eventually.
    Silly question: is it better to clip that sucker, or desolder it? I don't have a soldering gun these days. Come to think of it, I might not even have wire cutters...

  8. #8
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    Just cut or break it off and clean out any bits of debris. The import thing is to prevent the dead legs or other stuff from shorting against anything.

    As mentioned, if you get it working you should eventually replace the capacitor.

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