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Type: Posts; User: Hugo Holden

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  1. Replies
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    Yes, you are then looking for those same...

    Yes, you are then looking for those same undulations across the 63uS scan time. If it is say a disturbance coming through the video amplifiers or on their power supply. When checking for this, the...
  2. Years ago a friend found some dozens of small...

    Years ago a friend found some dozens of small miniature double triode tubes. So we got the idea to make them into flip flops and logic logic circuits to make a digital clock that had a low frequency...
  3. So one of your AMI UART chips was definitely...

    So one of your AMI UART chips was definitely intermittent and the partial file transfer fault completely went away when you replaced it ?

    This is really important information or a person could...
  4. I think the Killer poke myth got busted, as it...

    I think the Killer poke myth got busted, as it applies to damaging a VDU as I recall, but there could be an issue, if it was able to get IC output stages on the same line to fight each other for an...
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    Vintage computer prices.

    A while back I was thinking of getting a KIM-1 computer. One reason was that I found an article where the KIM could be used in a project to program the MM5204 UV eproms used in my SOL-20. I was about...
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    As I recall the data bit (just 0 or 1) from the...

    As I recall the data bit (just 0 or 1) from the the Matrox's ALT-512 RAM array is extracted by setting the RAM address for the pixel location and it is loaded to a latch. The PRDY output from the...
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    That is handy. I will try it. At least I know how...

    That is handy. I will try it. At least I know how to check it if it malfunctions. When it is working there should be zero cpu activity when the prdy is asserted by the Bytesaver, and its easy to see...
  8. I saw a couple of photos that reminded me of how...

    I saw a couple of photos that reminded me of how both wire wrapping and some styles of point to point soldering are really both not good (in my humble opinion).

    In the case of wire wrap, although...
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    Mike, The read operations on the Matrox card...

    Mike,

    The read operations on the Matrox card are through an I/O port.

    One thing I was reading about the SOL-20, in a magazine article somewhere, somebody remarked that there were too few S-100...
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    I just looked up my notes on it since it has been...

    I just looked up my notes on it since it has been a while:


    The PRDY driver circuit in the SOL is a tristate driving the PRDY line, the tristate input (U71, pin12) is driven by a flip flop U70,...
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    I found when running a small program to read the...

    I found when running a small program to read the video RAM contents out of the Matrox card and into general RAM, from time to time the SOL asserted the PRDY line, fighting the PRDY output from the...
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    Yes that is the way the line is supposed to work...

    Yes that is the way the line is supposed to work or be used, but in the SOL motherboard they drive that line from the output of a buffer that pulls it high or low at times and this fights with any...
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    Wow ! That is excellent, I can't wait to try it.

    Wow ! That is excellent, I can't wait to try it.
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    Thanks Dwight, all makes sense, but I don't...

    Thanks Dwight, all makes sense, but I don't understand what "reset" you are referring to.
    Is it exiting the program, if so I can easily exit to a Solos warm boot.
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    Also LD A,0FFH should be MVI A,0FFH I guess and...

    Also LD A,0FFH should be MVI A,0FFH I guess and LD A,H should be MOV A,H and OR should be ORA.

    I'll have to go over it very carefully. There is also JR that I can't see in my 8080 book, it...
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    Thanks Dwight, That would have taken me a 100...

    Thanks Dwight, That would have taken me a 100 times longer, or more.
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    Bytesaver ii questions.

    I'm going to attempt to try a Bytesaver II in my Sol-20 and program some 2708's. I have three questions:

    I have attached the recommended assembly code from the manual, it is for a Z-80 CPU. I'm...
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    I cannot see anything in any of those scope...

    I cannot see anything in any of those scope recordings that is close to the sinusoidal like banding pattern, modulating the intensity of all three beams, that you posted on the original post.

    If...
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    With a situation like this where the raster...

    With a situation like this where the raster geometry went out of alignment too after a deceleration, I would wonder if there might have been a magnetic strip on the CRT bulb or yoke perimeter which...
  20. That intermittent UART failure, is it with one...

    That intermittent UART failure, is it with one particular type , such as the TMS6011 or does it happen with all of them ? I think some of the AY- types I have seen have ceramic bodies with metal...
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    I'm not sure from this information so far as to...

    I'm not sure from this information so far as to what is going on. See if you can find a ripple pattern on the scope, that matches what you see on the CRT screen as a way of finding out where it is...
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    You forgot to add that the starting salary for...

    You forgot to add that the starting salary for the suitably qualified candidate will be $45,000 PA, with an opportunity to increase to $59,500 PA over a 10 year time frame, provided the candidate is...
  23. When I got my SOL I had been reading a lot about...

    When I got my SOL I had been reading a lot about intermittent behavior and these computers requiring regular fixes and like a lot of S-100 cards having intermittent issues and problems seeming to be...
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    In general there are four ways which solve the...

    In general there are four ways which solve the problem. Sometimes a combination of them is required for any particular monitor.

    In essence it requires that at the moment immediately after turn off...
  25. Have a look at page 12 or 13 of this article,...

    Have a look at page 12 or 13 of this article, there is a close up photo of a pcb where all the soldering flux has been removed as you can see a perfect result, a brush was not used:
    ...
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