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Type: Posts; User: Hugo Holden

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  1. Just move to the next standard value above the...

    Just move to the next standard value above the labelled uF value, and use the same voltage rating or one step above is ok within limits of the physical size. The 270uF 10V cap has a dome top, it has...
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    Also.... they fouled up more than one thing on...

    Also.... they fouled up more than one thing on the pin numbers on the Bytesaver II schematic. The circuit there as it stands cannot work because it will not oscillate, there is no 180 deg phase shift...
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    Dwight, for my diagram I went by the pin...

    Dwight, for my diagram I went by the pin numbering on the attached diagram.

    pin 2 supply, pin 1 feedback, pin 4 collector,, and 3 & 5 the secondary. The circuit you posted on the Bytesaver II has...
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    Looking at the circuit, this does not surprise me...

    Looking at the circuit, this does not surprise me at all. Some interesting research work was done by Motorola demonstrating that if you zener the B-E junction of a transistor, it ultimately causes it...
  5. The /STROBE signal is a very narrow negative...

    The /STROBE signal is a very narrow negative going pulse that you won't see easily on a scope unless the scope's trigger light gets activated by it, if the trigger threshold is correctly set. That is...
  6. I have always liked that range of transistors...

    I have always liked that range of transistors with the thin unique metal tab (fond of them). Sometimes they came in interesting colors like red-brown and green, as well as black and some SCR's came...
  7. ..I also had some issues with the power supply in...

    ..I also had some issues with the power supply in my SOL, one was faulty crimp connections on the spade terminals leading to the bridge rectifier, this causes and intermittent power failure that...
  8. The keyboard should work, regardless of most...

    The keyboard should work, regardless of most dilemmas with the computer as it only sends data and does not receive any.

    The LED's on the keyboard such as the upper case, local & shift lock should...
  9. That was a very good method, well done on that. ...

    That was a very good method, well done on that.

    When I had the intermittent IC issue I had to have my scope (a Tek 2465B) next to the computer, as soon as the fault appeared I started probing...
  10. It is interesting that this problem was very...

    It is interesting that this problem was very similar to a faulty (intermittent) counter IC I had in a SOL-20 keyboard, the output from one of the flip flops in it would just randomly stop at times....
  11. Well done !

    Well done !
  12. I agree with this, if it is definitely the case...

    I agree with this, if it is definitely the case with the VDU, that the VDU has its own internal horizontal oscillator that is sync'd to the H pulses from the computer. Most of these Commodore VDU's,...
  13. I could make a recommendation for vintage 74...

    I could make a recommendation for vintage 74 IC's. There is a seller in Oregon (dmallery on ebay) I have used many times and got a lot of great IC's from them, posted to me in Australia. The stock is...
  14. I think you are doing pretty well actually,...

    I think you are doing pretty well actually, confronted with one of the worst types of faults; intermittent.

    IC's can go intermittent, I have experienced this recently. The output can just drop out...
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    What a marvelous vintage computer project. I...

    What a marvelous vintage computer project. I really like those fractal graphics, well done !
  16. And a great project for SOL-20 owners !

    And a great project for SOL-20 owners !
  17. Thank you all for those replies.

    Thank you all for those replies.
  18. Modified 5.25" disk drive, or standard ?

    I was looking at a YD-580 disk drive on ebay, that looked good, little use.

    It is a TI branded YD-580.

    It comes with a report about its alignment it would seem. I have not seen this with a...
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    It is powered by a plug pack adapter and plugs...

    It is powered by a plug pack adapter and plugs directly onto the Sol-20 key board connector. So that the keyboard can be checked. It powers the keyboard via the connector. It displays the Hex output...
  20. Usually there is no concern with the height as...

    Usually there is no concern with the height as plenty of drive is available for the vertical deflection amplifier.

    It is a completely different cup of tea with the H deflection though. The rate of...
  21. That is a little odd, normally it would affect...

    That is a little odd, normally it would affect the width enough that a few turns, you would get at least some visible change. In some cases, even though the width coil is there on the PCB, if they...
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    Sol-20 Keyboard tester

    The first keyboard tester I made was on matrix board and looked a little messy. So I decided to make it better. I went away from the TIL311 and tried some of the Avago/Broadcom Hex displays and...
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    I have attached a couple of diagrams. If...

    I have attached a couple of diagrams.

    If Cromemco had assigned the colors to the memory bytes (or nibble differently) and changed the luminance resistor array around then in the monochrome mode,...
  24. Yes those are the sorts of plastic tools. But...

    Yes those are the sorts of plastic tools. But check the slug in the coil.
  25. L723 adjusts the width and R622 the height. But...

    L723 adjusts the width and R622 the height. But consider that if nobody has tampered with these adjustments it could be worth checking the power supply voltage from the regulator IC901. L723 will...
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