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Metallica
July 31st, 2017, 11:05 PM
I recently came across a collection (https://www.dropbox.com/sh/wnt1mwcmpqy3sfl/AACB5rrLg5gihsOfPCnYmKrca?dl=0) 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.

8008guy
August 1st, 2017, 07:33 PM
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

Chuck(G)
August 1st, 2017, 09:43 PM
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.

Metallica
August 1st, 2017, 10:08 PM
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.
4011440115401164011740118

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

Metallica
August 2nd, 2017, 06:09 PM
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.
4013040131401324013340134

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

DDS
August 3rd, 2017, 06:51 AM
I recently came across a collection (https://www.dropbox.com/sh/wnt1mwcmpqy3sfl/AACB5rrLg5gihsOfPCnYmKrca?dl=0) 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/showthread.php?52494-Fulcrum-8088-S100-Closet-Cleanout-Sale!

https://amaus.org/static/S100/cromemco/systems/Z1/03%20Cromemco%20Z1%20top%20removed.JPG

http://www.s100computers.com/Hardware%20Folder/IMSAI/History/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. ;-)

Bungo Pony
August 8th, 2017, 04:55 AM
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.

AdamAnt316
August 8th, 2017, 10:59 AM
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 (https://www.antiqueradio.org/dimbulb.htm).

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 (https://en.wikipedia.org/wiki/Tantalum_capacitor); 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

daver2
August 8th, 2017, 11:29 AM
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/Hardware%20Index%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

Metallica
August 8th, 2017, 11:17 PM
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.

Metallica
August 9th, 2017, 01:00 AM
Thanks for the resources, I would never have found those. Would it be best to post pictures of the boards in this thread or a new one?

Metallica
August 9th, 2017, 01:23 AM
It turns out the large metal case on the floppy drive was held on by a single screw. I assume that's what the ridiculously long ribbon cable from the Altair is for, because it fits. The drive motors spin freely, the belts are intact, the eject mechanisms mostly work, and this is surprisingly clean too. That's about the extent on my knowledge with floppies though, I've never used them for their intended purpose.
402134021540216402174021840219

Would this need the variac treatment as well?

AdamAnt316
August 9th, 2017, 10:05 AM
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.
Old tantalums tend to just explode without warning. The circuit it's in may start to malfunction when it does, but it'd be pretty obvious from the smoke and flames coming from the circuit board. :shocked: Best to just replace them before you apply voltage, in my opinion.

Personally, I think a variac is the way to go, but you really need to have an AC ammeter connected between the 'hot' output of the variac, and the hot lead of the outlet the device under test is connected to. If you can't find an AC ammeter, you could wire a 1 ohm power resistor (10W or larger) in its place, and connect the leads of an AC voltmeter across it to get a similar effect. You might find one at a yard sale, but something like an antique radio swapmeet would be a better bet. Alternatively, you could buy one online (the generic term is "variable autotransformer (http://www.electronics-tutorials.ws/transformer/auto-transformer.html)").

A dim bulb tester can be used with just about anything which has a linear power supply; something which uses a switch-mode supply might not be too happy about being used with one. The dim bulb tester is good for making sure the device under test doesn't register a dead short, but it won't help to reform the capacitors, AFAIK. Be sure to only use incandescent bulbs in the tester, BTW; 60-100W bulbs are still available in 'Rough Service' form, and you can still get bulbs larger than 100W from certain stores. It's a good idea to have a wide selection of bulb wattages handy, especially if you have a variety of items to test.
-Adam

daver2
August 9th, 2017, 10:56 AM
See if you can find a Variac - that would be my recommendation.

Those resources are the primary 'goto' ones we all know about and very much appreciate (thanks guys - you know who you are).

Post away with your images in this thread. It keeps everything together.

As 'AdamAnt' has said; Tantalum capacitors - working one second and BANG the next (usually at start-up though I find). They scare the life out of you when they do go BANG! You can't 'reform' them in the same way as you can with electrolytics though. They do tend to go short circuit rather than open circuit - so they are generally a revealed fault if that is of any comfort to you. If you plan to keep the kit, I would get it working first. If any capacitors go - deal with them on a case by case basis. Electrolytics need to be reformed after all this time - no exceptions really. This should be done before any powering up at all.

When the machine is working - if you plan to keep it - then you can make the decision about replacing the tantalum capacitors at that point.

That's my advice.

Yes, reform any electrolytics in the disk drive poser supply units (if there are any). Or is the power supplied externally? If internally, I would check the power supply out AFTER disconnecting the disk drives themselves. On my Cromemco I had a shorted voltage regulator that would have put the full unregulated supply volts onto the disk drive and (probably) 'done it in'. I powered the supply up without the drives connected and found one unit with the correct regulated voltages and the other with too high a voltage. I replaced the faulty voltage regulator, connected up the disk drives and we were away.

EDIT: I have just re-looked at your photographs and it just looks like there are two disk drive units in the housing and no power supply unit. Is this correct? If so, there must be some sort of power cable (in addition to the ribbon cable) going to the disk drive cabinet.

Have a 'plan' about what you are doing and build the system up from the smallest sub-set. I took all of my S100 cards out of the backplane (very carefully noting where each card went) and got the Cromemco S-100 power supply refurbished and tested. Then started adding the S-100 cards. I can explain the process I used later if that would be of help?

Dave

Chuck(G)
August 9th, 2017, 01:42 PM
One small nit--in the fourth photo above, the ribbon cable is oriented the wrong way. The red stripe should be on the "pin 2" side of the connector. I mention this only because an upside-down cable is a good way to clobber floppies :)

Corey986
August 9th, 2017, 06:19 PM
I'm going to ask an important question.

Where are you located? Maybe you can find a local vintage computer group who can help you reform the caps so you don't have to buy a variac.

Just a thought...

Metallica
August 9th, 2017, 07:33 PM
Or is the power supplied externally? If internally, I would check the power supply out AFTER disconnecting the disk drives themselves. On my Cromemco I had a shorted voltage regulator that would have put the full unregulated supply volts onto the disk drive and (probably) 'done it in'. I powered the supply up without the drives connected and found one unit with the correct regulated voltages and the other with too high a voltage. I replaced the faulty voltage regulator, connected up the disk drives and we were away.

EDIT: I have just re-looked at your photographs and it just looks like there are two disk drive units in the housing and no power supply unit. Is this correct? If so, there must be some sort of power cable (in addition to the ribbon cable) going to the disk drive cabinet.

Have a 'plan' about what you are doing and build the system up from the smallest sub-set. I took all of my S100 cards out of the backplane (very carefully noting where each card went) and got the Cromemco S-100 power supply refurbished and tested. Then started adding the S-100 cards. I can explain the process I used later if that would be of help?

Dave

The power supply is internal and the cord is hardwired. I certainly can't turn down information, so I'd definitely be interested in the process when you have the time.

I've also found two power boards that appear to be for a floppy drive, as they share at least one connector that I can see. I suppose I need to disassemble the drives to have a better look at the power supply, is there anything I should be aware of before attempting?

I've taken pictures of everything I can see at the moment, and it appears as though there was something else next to the power board in the cabinet at one time.

40232402334023440235402364023740238

Metallica
August 9th, 2017, 07:35 PM
One small nit--in the fourth photo above, the ribbon cable is oriented the wrong way. The red stripe should be on the "pin 2" side of the connector. I mention this only because an upside-down cable is a good way to clobber floppies :)

Thanks, I wasn't sure if the orientation mattered. I haven't attached anything yet, still plan on cleaning everything.

Metallica
August 9th, 2017, 07:36 PM
I'm going to ask an important question.

Where are you located? Maybe you can find a local vintage computer group who can help you reform the caps so you don't have to buy a variac.

Just a thought...

Central Florida

Dwight Elvey
August 10th, 2017, 05:47 AM
My preferred way to deal with electorlytics is to first remove
all the boards.
Remove one screw from each capacitor and put a 1 meg resistor
in series with each capacitor.
Then you can safely turn on the power as the amount of out gassing
the capacitors will do is well within what they are designed to handle.
Just leave it on for a week or two.
Check the voltage on the caps periodically with a meter. If the voltage
is stable after a week, you can add another 1 Meg in parallel and go
another week. Repeat until you see the voltage get close to the desired
level. It takes several weeks.
I recommend using a VTVM with a real dial as it will discharge the capacitor
some. You are looking for the peak voltage.
Dwight