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Thread: Altair 8800 Information

  1. #1
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    Default Altair 8800 Information

    I recently came across a collection of vintage electronics, including what appears to be a factory assembled Altair 8800, IMSAI 8080 clone by Fulcrum Computer Products, and a TeleVideo 920 C terminal. These are a little beyond my comprehension the oldest systems I've worked on previously were Windows 95 era towers.

    Is there anything I need to do before attempting to power them on? As far as I can gather, these aren't very common, and the Altair is a significant piece of computing history. I would really like to minimize the chances of damaging anything, and am curious as to the best ways to preserve the equipment in working order.

    Any additional information of any kind would be greatly appreciated; I've put many hours into research and haven't found nearly as much as I'd hoped.

  2. #2
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    Pull all the cards. Inspect the caps in the power supply for leakage. I personally recap the power supplies. If not bring the power up slowly with a variac to reform the caps. Measure all the voltages to verify that they are within spec. Then one by one inspect and test the cards. You may also want to replace any old electrolytics on the cards.

    Inspect everything and replace where necessary. It is mainly common sense.

    Good luck, those are fun projects. I just restored an Altair and and currently restoring an Imsai.

    Len

  3. #3
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    It's almost a sure thing that the caps in the Altair are dried out if this is the original. They didn't exactly use the best design.

  4. #4
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    Is there anything I can use besides a variac? I can probably source an in-line dimmer easier, but I imagine this equipment will pull a lot more current than something like that would be designed to handle. This is all very new to me and a little overwhelming, so I may as well apologize in advance for the slew of questions that are sure to follow.

    I realize the caps would need to be replaced if faulty, but if they still function, would replacement parts degrade the value? I'm more interested in the historical significance and would like to leave as much untouched as possible. I'm certainly no expert, but they don't appear to be bulging or leaking.

    Is there a way to verify functionality of the cards beyond whether the machine powers up? I'm haven't been able to identify much beyond what I assume is the RAM, so I'm not sure what most of it is designed to do. I also found several additional boards beyond what is in each machine, some of which are new old stock, and haven't found much online about these either.

    I've also attached pictures of what I assume is a hard drive with two separate connectors routed from the case, though I didn't immediately notice any way to connect it. There is a rather large ribbon cable that has been routed out of the Altair, with several connections I've never seen, but this differs from any others I've found with the rest of the equipment.
    IMG_1241.jpgIMG_1242.jpgIMG_1246.jpgIMG_1249.jpgIMG_1250.jpg

    Would there have ever been a standalone floppy duplicator? The dual drive unit that was included does not appear to have any data connection, unless the metal case is easily removed. It is very heavy and lacks any sort of brand or general markings, just a hardwired power cord. I didn't see anything that appeared user-accessible, but I am also fearful of damaging anything.

    Thank you,

    Anthony

  5. #5
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    Default

    Is there anything I can use besides a variac? I can probably source an in-line dimmer easier, but I imagine this equipment will pull a lot more current than something like that would be designed to handle. This is all very new to me and a little overwhelming, so I may as well apologize in advance for the slew of questions that are sure to follow.

    I realize the caps would need to be replaced if faulty, but if they still function, would replacement parts degrade the value? I'm more interested in the historical significance and would like to leave as much untouched as possible. I'm certainly no expert, but they don't appear to be bulging or leaking.

    Is there a way to verify functionality of the cards beyond whether the machine powers up? I'm haven't been able to identify much beyond what I assume is the RAM, so I'm not sure what most of it is designed to do. I also found several additional boards beyond what is in each machine, some of which are new old stock, and haven't found much online about these either.

    I've also attached pictures of what I assume is a hard drive with two separate connectors routed from the case, though I didn't immediately notice any way to connect it. There is a rather large ribbon cable that has been routed out of the Altair, with several connections I've never seen, but this differs from any others I've found so far with the rest of the equipment.
    IMG_1241.jpgIMG_1242.jpgIMG_1246.jpgIMG_1249.jpgIMG_1250.jpg

    Would there have ever been a standalone floppy duplicator? The dual drive unit that was included does not appear to have any data connection, unless the metal case is easily removed. It is very heavy and lacks any sort of brand or general markings, just a hardwired power cord. I didn't see anything that appeared user-accessible, but I am also fearful of damaging anything.

    Thank you

  6. #6

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    Quote Originally Posted by Metallica View Post
    I recently came across a collection of vintage electronics, including what appears to be a factory assembled Altair 8800, IMSAI 8080 clone by Fulcrum Computer Products, and a TeleVideo 920 C terminal. These are a little beyond my comprehension – the oldest systems I've worked on previously were Windows 95 era towers.

    Is there anything I need to do before attempting to power them on? As far as I can gather, these aren't very common, and the Altair is a significant piece of computing history. I would really like to minimize the chances of damaging anything, and am curious as to the best ways to preserve the equipment in working order.

    Any additional information of any kind would be greatly appreciated; I've put many hours into research and haven't found nearly as much as I'd hoped.
    At this point in time, very few of the original S-100 computers are exactly common. Yes, the Altair and Imsai computers are hallmarks in the industry, but the Fulcrum you mention and the Cromemco Z-1, both Imsai clones, are probably even rarer than an Imsai itself.

    http://www.vcfed.org/forum/showthrea...-Cleanout-Sale!

    https://amaus.org/static/S100/cromem...%20removed.JPG

    http://www.s100computers.com/Hardwar...ry/History.htm

    OTOH, these computers use technology common in the mid to late 1970's. Fixing them "ain't rocket surgery." There are plenty of previous restoration projects documented on the web. Take your time and you and the machines will do fine.

    http://www.classiccmp.org/cini/my_imsai.htm

    Oh, yes! Don't forget to have some fun in the process.
    "It's all bits on the bus, Cowboy! It's all bits on the bus!" -- Tom Beck, #1ESS Instructor, Southern Bell Opa Locka Training Center

  7. #7

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    I acquired an Altair 8800 back in the Spring and haven't powered it up yet. I'm planning on replacing the capacitors in the power supply before I do so. I'd recommend doing the same for yours. The caps on the individual cards shouldn't be as problematic. They may not function quite properly, but they shouldn't kill anything else in the computer unlike the power supply.

  8. #8

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    Quote Originally Posted by Metallica View Post
    Is there anything I can use besides a variac? I can probably source an in-line dimmer easier, but I imagine this equipment will pull a lot more current than something like that would be designed to handle. This is all very new to me and a little overwhelming, so I may as well apologize in advance for the slew of questions that are sure to follow.

    I realize the caps would need to be replaced if faulty, but if they still function, would replacement parts degrade the value? I'm more interested in the historical significance and would like to leave as much untouched as possible. I'm certainly no expert, but they don't appear to be bulging or leaking.
    Don't use a light dimmer! Those are meant for resistive loads (i.e. lightbulbs), while a transformer is an inductive load. In a nutshell, you'd almost certainly burn out the power transformer in the Altair, which wouldn't be good for its authenticity, among other things. A variac would be your best bet for attempting to reform the capacitors, preferably with an AC ammeter in series with the output. There is a way to at least check the integrity of the Altair's power supply without a variac, and that is to use a dim-bulb tester.

    Capacitors can go bad without looking like they have. Bulging and exploding only happens in the most extreme cases; it's quite possible for electrolytics to go open or at least electrically leaky without showing any external signs of failure. Also be on the lookout for tantalum capacitors; those can go bad as well, and in rather more explosive ways than regular electrolytics (most of the time, anyway).

    As for diminishing the value, I don't know for sure. I say, as long as you're careful when replacing the old capacitors so that the board isn't damaged, and hang onto the old caps (for any future owners, in case they're the type of collector who would 'restuff' the old ones), it shouldn't hurt the value. Anyway, good luck!
    -Adam

  9. #9
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    The first thing to do is document EXACTLY what you have got. What connects to what and which way round. etc.

    Each of the cards should/will have some sort of manufacturer and part number on them. Note which slot you pull the card from and replace it in exactly the same slot as you got it from. Do not disturb cables as much as you can.

    Many cards can be static sensitive. Buy an antistatic workmat and wrist strap to prevent damage. Remember - these systems/cards are rare. If you damage something important - where will you get a replacement from?

    If you post what you have got then we will point you in the right direction for where to find the data/manual for it. The usual 'culprits' for excellent documentation are http://www.s100computers.com/Hardwar...dex%20Page.htm, http://bitsavers.informatik.uni-stuttgart.de/pdf/ and https://amaus.net/static/S100/.

    Do NOT power anything up now. You have got a brilliant haul - make sure you do nothing 'rash' to damage it!

    Take copious photographs of everything. You will rely on these in the future.

    Start a notebook of things you find out, things you learn etc. Again, you will refer back to this many times.

    You know when a tantalum bead capacitor lets go! I used to have a mark on my thumb to remind me!!!

    Dave
    Last edited by daver2; August 8th, 2017 at 12:38 PM.

  10. #10
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    Thank you, I wasn't very familiar with tantalum capacitors. Would those show any signs of failure, or are they just like the others?

    I had actually moved on from the light dimmer idea before the double posts were approved. I planned to hit some yard sales this weekend in search of a variac, would that still be better than the dim-bulb tester? I've seen references to it while trying to research everything, I just assumed it was only for vintage radios.

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