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Type: Posts; User: Hugo Holden

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  1. Replies
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    If you had text data coming out of the vid pin of...

    If you had text data coming out of the vid pin of U21 before you replaced the 74ls08 (was that the case ?) then it disappeared after it was replaced, likely something did happen to the pcb...
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    FALTER's post : "That was one of the reasons I...

    FALTER's post : "That was one of the reasons I zeroed in on the 74ls08.. because I could see inputs into one of the AND hated but nothing coming out of pin 11. I'm so you're saying that pin could be...
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    You are asking the right questions. These are...

    You are asking the right questions.

    These are some things that will help you every time you go to repair a fault:

    When you find the schematic of the circuit you are trying to repair, print it...
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    Agree completely. When the brightness and...

    Agree completely. When the brightness and contrast controls are set correctly on the CRT, the video signal content (pixels on) shifts the beam into the illuminated state. A pixel zero is just a video...
  5. Thread: Fake ICs

    by Hugo Holden
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    583

    The fakers are notoriously inept at faking...

    The fakers are notoriously inept at faking ceramic IC's, its the epoxy case ones they can much more easily re-surface and label. So gold pins and gold top ceramic IC's in my experience are very...
  6. Thread: Fake ICs

    by Hugo Holden
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    583

    Well there is a chance that they could be a...

    Well there is a chance that they could be a re-labelled equivalent part that somebody knows is an equivalent. For one example the character generator in the Sol-20 does have an equivalent part...
  7. Thread: Fake ICs

    by Hugo Holden
    Replies
    17
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    583

    These have a few hallmarks of being fakes I'm...

    These have a few hallmarks of being fakes I'm afraid. Many of the fakers appear to have laser machines that re-surface the IC to a flat surface finish and laser engrave a new label. I think they do...
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    As soon as I looked at the Microexpander pcb I...

    As soon as I looked at the Microexpander pcb I thought it looked a lot like a SOL-20. And it has the same designer Lee Felsenstein so not a wonder they look similar. Here is a good report about it...
  9. Disk Drive Construction Project Document.

    I had a good result with the twin disk drive unit I made for my SOL-20. So I manufactured a second unit as a spare. This time I took the time to document the details of the dimensions, hole...
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    I found the answer and it was the most difficult...

    I found the answer and it was the most difficult hardware issue I have had to sort out on my SOL yet.

    I'll explain what was wrong and of course when the answer is known it all seems so darn...
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    Fictional Computers

    While looking for something else I stumbled upon this list of fictional computers, which include some of my favorites like the HAL-9000:

    https://annex.fandom.com/wiki/List_of_fictional_computers
    ...
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    Yo are welcome, typo in my text though R20 should...

    Yo are welcome, typo in my text though R20 should have read R204.

    You can always test that transistor on a meter. Even if the outside of it looks bad it is still possible it is ok. Then if that...
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    Hi, Good photos, it helps a lot. From what I...

    Hi, Good photos, it helps a lot.

    From what I can see there the transistor is most likely the video output transistor. It is the upper transistor of a cascode output stage (look up cascode...
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    Graphics card synchronization issue.

    I am working with a Matrox ALT 512 graphics card to make a light pen project. I have figured out how to write to the card with programs and image files etc. I figured it wouldn't be much use with the...
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    Outstanding work ! I really admire what you have...

    Outstanding work ! I really admire what you have done there and dealing with the disappointment after what happened to your Sol. Very impressed.
  16. Seattle Computer's SCP-110A 64k memory card.

    I have just tried a very interesting (and beautiful) 64k memory card in my Sol -20, set up for 48k of course.

    This is the first S-100 card I have put in the sol that has worked first time without...
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    So you are saying that the sort of appearance...

    So you are saying that the sort of appearance seen there in that file with the zones of FF's you would judge as probably original programming ?
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    Just a question about the file as the whole Rom...

    Just a question about the file as the whole Rom thing worries me in terms of data retention and I'm fairly new to programming and using Roms. In that file, towards the end, there are some broad zones...
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    There are generally severe phase errors and...

    There are generally severe phase errors and signal jitter from old VHS tapes. And they keep getting worse with each pass of the tape. My advice if you wanted to get this into a digital medium to...
  20. The height looks like its probably ok and the...

    The height looks like its probably ok and the width, a little wide. Normally the height control is a preset potentiometer that adjusts the amplitude of the drive voltage to the vertical scan...
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    These may be the same/similar to the common 6A05...

    These may be the same/similar to the common 6A05 diode:

    https://www.rectron.com/data_sheets/6a05-6a10.pdf
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    The diode physical size and lead diameter look...

    The diode physical size and lead diameter look similar to 1N54 series diodes, for example a 1N5404 is a 400V 3A diode and a 1N5401 a 100V 3A version.

    Sometimes I replace these 1N54 series types...
  23. In some cases, but not all, near the crystal on...

    In some cases, but not all, near the crystal on the pcb there is a small adjustable ceramic capacitor to trim the crystal frequency, but there might not be one in this monitor. The flickering lines...
  24. The blue ones in the photo on Post #6 appear to...

    The blue ones in the photo on Post #6 appear to be 16V types.

    A while ago I built a project where there was a 5V linear regulator which unexpectedly oscillated. It had (originally 16V tants) on...
  25. It is not uncommon for those Tant caps to short...

    It is not uncommon for those Tant caps to short out however, it does seem like a coincidence the experience you have had.These caps are very sensitive to over voltage, much more so than an...
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