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Thread: PETE 8032 Monitor - Vertical/Horizontal Size Adjustment

  1. #1

    Default PET 8032 Monitor - Vertical/Horizontal Size Adjustment

    Hello, can anyone point me to the correct pots on the 8032 monitor PCB that control vertical height and horizontal width of the image? After looking at many pics of 8032 on the web i've realised the size of my image is much smaller that most leaving me a border of 1 1/2" top and bottom and 1" at left and right.

    PCB Layout

    Schematic



    Many thanks.
    Last edited by JackLeather; October 5th, 2020 at 11:14 AM.

  2. #2

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    Can someone tell me how to edit the thread title please?

  3. #3
    Join Date
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    I don't think it is possible to change the title.

  4. #4

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    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 have an adjustable ferrite core, probably with a hexagonal hole in it, you will require the right plastic tool, avoid an incorrect metal tool or the slug can crack and lock into the threads, though if that happens there is a trick to remove it.

  5. #5

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    Quote Originally Posted by Hugo Holden View Post
    But consider that if nobody has tampered with these adjustments it could be worth checking the power supply voltage from the regulator IC901.
    voltage at TP1 reads 18v so looks OK (as the schematic suggests) - what is that plastic tool called? like; https://www.amazon.co.uk/Hozan-D-16-.../dp/B004OCMPHQ

  6. #6

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    Quote Originally Posted by JackLeather View Post
    voltage at TP1 reads 18v so looks OK (as the schematic suggests) - what is that plastic tool called? like; https://www.amazon.co.uk/Hozan-D-16-.../dp/B004OCMPHQ
    Yes those are the sorts of plastic tools. But check the slug in the coil.

  7. #7

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    Image centering is controlled by two small metal rings at the back of the yoke. Once you get the width and linearity the way you like from the controls on the board, you can then recenter using the rings. They each have a small metal tab for your fingers to move. Since they both interact with each other, try to make adjustments with both at the same time. Either move them together/apart the same amount or rotate them together. Moving them together or apart makes the effects of the rings stronger or weaker. Moving them as a pair orbits the image around.
    Trying to move them individually will only result in frustration because they interact. Sometimes it helps to make some markers on the screen. First rotate the tabs so they are on opposite sides of the neck. Pick something you think should be centered on the screen. Put a mark where it is and were it should be. Now put the two tab together and rotate them as a pair until they form a line from where the image was through the center to where that same spot on the image crosses the imaginary line.
    Rotate them apart evenly until the image aligns to the center mark. ( I may have got the order wrong of the being opposite or together for the steps but one way should work, it has been a long time since I've done this ).
    In any case, moving them individually will drive you mad.
    Dwight

  8. #8

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    Wow, great information, thanks guys! 'Trimmer pot' tools are ordered and on the way.

    I'm sure this post will be of use to others in the future (must ask an Admin to rename the thread tho).

    Next, question - does anyone know of a test card/pattern that i can load up for screen calibration? i was thinking of a program thats probably written in BASIC.

  9. #9

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    Trimmers tools received!
    L723 (the adjustable ferrite core) turned - all the way down and all the way up but didn't appear to have any effect or very little at least - for a full turn what sort of increase/decrease in width should i expect?

  10. #10

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    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 were struggling to get full width at the factory, they short it out with a link wire, so check to see if it's linked out. I notice that in some versions of these monitors they didn't include a width or even the Lin coil, so they were struggling with trying to get full width.

    Since your issue is that your width is too low, then the max width you will get is when the slug is removed from the coil. So unscrew the slug and remove it. If still not enough width, short the width coil out, that is the max width you will then get.

    It's easy to make a test pattern in basic just using the filled boxes.

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