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Old 12-10-2007, 06:24 AM
Grant Stockly Grant Stockly is offline
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Quote:
Originally Posted by Cappellanus View Post
Hello:
But with small scale integration processor design, a minor bug can hide in a little used instruction.
If you make a program to test all instructions, share it. Something that would run all instructions and the result in a register would be predictable if everything went fine?

Quote:
Originally Posted by Cappellanus View Post
1) Spray painting the front panel with clear enamel or laquer isn't really an optional step. The deep texture of the brushed metal will suck a finger print off the cleanest hands.
Was it easy to do this without getting runs?

Quote:
Originally Posted by Cappellanus View Post
2) Wow! there were a lot of extra capacitors when I was done. I placed one everywhere I could, and still had lots left over. I guess having more than needed is better than too few. It's interesting that Erik's machine used *zero* decoupling capacitors, just two electrolytics on the board for +5V and one for +12V. I suspect John designed the board with lots of decoupling caps, but realized it ran fine without them. Standard design rules of the time, however, suggested lots of decoupling caps were needed.
My prototype used only 1 capacitor other than the two in the oscillator. I supplied a lot of extra ones because of alternative positioning. Erik's PCB actually had labels for some of the capacitors missing...

For the electrolytic caps I chose them based on what would fit (lead spacing). The newer caps are a lot smaller for the same capacity.

Quote:
Originally Posted by Cappellanus View Post
3) The board scans and documentation never show c16 and c17, and how exactly they should be positioned. But a search of the internet showed
I can only figure these were part of a fix to another problem, but not necessarily what ended up fixing the problem. My Kenbak ran for over a week and it doesn't have them.

Quote:
Originally Posted by Cappellanus View Post
4) Interesting about the second ground connection from the power supply to the ground of IC-114 and IC-115. I think I know why Blankenbaker did that. The ground current from these two IC's could potentially be pretty high. You may notice that the open collector lamp driver IC's can source up
Maybe, but his traces are pretty big. I think the traces used could handle it. It may be related to noise more than a current.

Quote:
Originally Posted by Cappellanus View Post
6) I'm not sure if I'm supposed to use the pan-head screws that came with the case, or the smaller ones in the bag. Do you feel the smaller screws are more authentic? They don't look all that different to me.
The smaller ones are 18-8 stainless. I wouldn't have even included the larger ones but OPTIMA tightened up the larger ones and in some cases it scuffed the aluminum. So I included both...

Quote:
Originally Posted by Cappellanus View Post
7) A little piece of metal to cover up the "expansion" slot in the front panel wouldn't be a bad idea. I'll probably make one up. The only Kenbak-1 I've seen missing this is Erik's machine. I just noticed for the first time: The CTI labeled machines left off this slot completely.
John suggested I leave it out too, but it didn't look the same without it. (Plus I have some ideas for it...) Are you thinking of covering it from the back? It might look good with copper or brass.

Quote:
Originally Posted by Cappellanus View Post
8) I used automotive spade-connectors to attach to the power switch on the front panel. That allows completely removing the front panel.
I did too. I tried to stay away from suggesting anything about AC. Without offending anyone I tried in the manual to suggest getting help from an electrician. I imagine most people doing the kit know enough, but I don't want to get in trouble for it. At least I can say "How did you get shocked? I didn't sell you a power cord!"

Quote:
Originally Posted by Cappellanus View Post
9) In retrospect, I'd like to raise the power supply a bit. It's just a bit above the PC board, and hides too much of the Kenbak-1 pc board. If it was just 1/2 or 3/4 inch higher, you could see a bit more of the "guts". As it is designed, you can't even see the "kenbak" logo on the pc-board.
I would like to also. Sometimes things aren't obvious until its all together (and you have 20 in stock) I'm glad there were no show stoppers. I would have also made the standard fan spots capable of fitting a fan inside. Those are standard sizes for an 80mm fan I think. A smaller one could probably be fit on the inside with some strong double stick tape. I ran mine for a week in a 76F room with no problems. I do have heat sinks on a few of the chips.

Quote:
Originally Posted by Cappellanus View Post
10 It's interesting that the transistors were opposite pin-out (ebc instead of cbe) which makes the transistor orientation look wrong, when compared to Erik Klein's machines. Did you use the same transistors as Erik's?
The transistors I used are equivalent substitutions chosen from a cross reference. The pinout difference you mentioned is why my prototype didn't fire up the FIRST time I applied power. I'm lucky that the only thing I had to debug on the prototype was all 8 transistors being installed backwards.

Code:
               Vintage:           Kit:
T1             2N5449             2N4401
T2             2N5447             MPS3702
T3             2N5449             2N4401
T4             2N5449             2N4401
T5             2N5449             2N4401
T6             2N5447             MPS3702
T7             2N5449             2N4401
T8             2N5449             2N4401
Quote:
Originally Posted by Cappellanus View Post
This was a lot of fun. I'm surprised with how complete the kit was. I figured I would have to supply a lot of miscellaneous wire and hardware, but didn't. Well done!!!
I'm glad you enjoyed it and I'm glad you received more than you expected. I think of myself buying the kit and what I would want to receive. I guess I succeeded with you.

Do you have any other pictures worth sharing? Anything special? I'm glad your daughter had fun working with you. You'll be able to show her as she gets older the 1s and 0s work inside a computer. Have you read the first part of the manual with her?

What are your thoughts on the manual? Any areas I can make it better?

Last edited by Grant Stockly; 12-10-2007 at 06:27 AM.
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