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Old 07-04-2007, 03:24 AM
phe phe is offline
Join Date: Dec 2006
Posts: 48
Default My kit is up and running

Tonight it is finally there!! After several debugging session with Grant, and a round trip airplane ride for my boards to Alaska and back, I finally have the system running.

How cool it is to do all the same work now some 30 years later, like so many did back inthe 70s, and then finally get it working. I even picked up a cheap small AM radio at the thrift store. "I can hear music... sweet sweet music"

Some of the details:

I have kit 5, with a case signature says kit 6.

I had it all together but could not get things to work. After spending a couple of hours on the phone, Grant graciously offered to test my cards out. I mailed them to him and he found a couple of problems with the memory board. One of the 7404 ICs was bad, and I messed up one of the sockets. After soldering the socket in, I realized one of the pins had bent instead of coming through the hole in the board. When I removed the socket, I pulled out a via or at least cracked a connection. Grant fixed that up for me and replaced the bad 7404.

When I got the boards back, I could not get the protect light to go out and I could not load anything into RAM. Again, back on the phone with Grant and we temporarily disabled the protect signal. Now I can deposit values as I like. I cannot protect my memory at the moment, but that is ok.

I've got a new meter arriving on Thursday. When it gets here, I will try to figure out what is wrong with the protect circuit.
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Old 07-04-2007, 11:46 AM
sje sje is offline
Join Date: Nov 2006
Posts: 62
Default Congratulations

Congratulations on getting your Altair running! And kudos to Grant for his quite able assistance.

The memory protect circuit is fairly simple, so I predict you'll have that fixed soon.

Thirty plus years ago when I assembled IMSAI 8080, I managed three errors on the 4 KB memory card: incorrect polarity on two electrolytic capacitors along with a solder bridge. Once these were fixed, it worked like a charm.

Back then I had only a cheap analog multimeter. Now I've got decent equipment including my trusty Tektronix oscilloscope and a far better knowledge of digital electronics. Oh, and experience to tell me not to rush kit assembly.

I'm a bit surprised that you had a bad 7404. I suppose it can happen, but it's a bit rare. Maybe it was a very old chip and had seen some kind of debilitating environmental incident. The more modern jellybean gate chips share the same essential design: a masked ROM using input pins as an address with the stored data being the output truth table. Perhaps the bad chip you encountered was actually a good chip but had the wrong external labeling.

Given that in circuit testing can be a big pain, it might be advisable to test all the basic ICs on a breadboard before firing up the old soldering pencil.
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Old 07-04-2007, 03:07 PM
marty marty is offline
Senior Member
Join Date: Jun 2007
Posts: 118

Hi to All;
I had an origional Altair 8800b, unfortunately, it is long gone. I have had to learn much since those days, I have better equipment now, and better sense.
What would it take to post programs for the Altair, one in assembly another for all others. That people who have these machines can share what they have written for their machines or have tried and gotten to work on their machine.
I keep a notebook with programs that I have tried on my machine, some work some don't, most likely operator error. I am still trying to learn 8080 machine language and how to think in 8080, and write small programs for my machine. I plan on going through the codes and writing very small programs around each octal code. Yes, I like octal, it make more sense to ME, than does hex. I am an octal person. And I know there are people who are Hex people, and are very passionate about it.
Thanks Marty
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Old 07-04-2007, 11:33 PM
phe phe is offline
Join Date: Dec 2006
Posts: 48

I tried to load and run the program that, when executed, plays Fool on the Hill and Daisy via the AM radio. I must have made a mistake because, after painfully loading the program via the switches, it promptly ran amok and wiped everything out in memory. I think I forgot to press reset to get back to memory location 0000 so the program ran whatever was in memory at whatever location was being examined at the time I switched the computer to run

Now I know the value of the protect circuit!

Well, I wanted to hear those songs so I reloaded the programs and triple checked (since I can't protect my memory). And they came through loud and clear.

So, now I've heard the music. It is much better than I had anticipated. Rather impressive. I actually heard a mistake in the music notes. I was able to read the code as the music played and find the place where I had entered some bad data and correct the entries. Cool.

Now I need to so something fun, like loading basic and hooking a terminal up and playing star trek.
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