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Thread: Commodore CBM 2001-16N - BIG MESS!

  1. #141
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    When possible, I recommend clipping IC leads close to the part and then pulling the pins out one at a time with tweezers.
    The suspect part will be sacrificed, but this will use minimum heat from the iron to protect the board.

  2. #142

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    Quote Originally Posted by dave_m View Post
    The suspect part will be sacrificed, but this will use minimum heat from the iron to protect the board.
    I usually pull the part intact if it is a regular leaded part but I've had years of experience with a soldering iron and a pullit solder sucker. There is an art to it. You have to know when you've removed the right amount of solder. You have to know how to push on the lead just right with the iron so that it separates for the hole and not rip it. You have to know how much to bend it away from the side so it doesn't stick back. You can often tell by the tink sound it makes when it is ready to continue. You have to know what the right amount of squeezing will break the lead loose at the part. You have to know when it just isn't going right so you have to refill the hole with solder and start over again.
    Otherwise, just clip the lead close to the part and use the tweezers.
    I should have mentioned always use a clean tinned iron. Never neglect keeping the tip clean and properly tinned.
    Dwight

  3. #143

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    I understand your concerns and I am aware about the risks when pulling chips off the board. Over the last year i developed my skills in de- soldering. Now i got a best practise to minimise the risks. The key is to re-flow the pins with fresh solder first so that the old solder and the new solder are mixing. When using the vacuum pump usually all solder material gets removed easily. For residues i am using desoldering wire. With this method i am usually able to pull the old chip off the board without damages.

    So far i installed or replaced ca. 20 sockets on my PET board without damaging any single chip. But it happens to me 3 times that traces lifted up. Thats the risk i am taking and thats ok for me.

    Today i found out itīs not the Shift Register E11 causing the vertical lines. There was still a bad contact at the Character ROM (F10). When pushing the chip a bit the vertical lines disappeared. Although i already checked continuity back in january (especially between F10 and E11) there was still something not given good contact. Again - the Socket was bad. I installed a new high precision socket today and now i have a rock stable and nice screen

    Still need to figure out why i cannot write and read to/from cassette tape. I am using the Commodore C2N (1530?) which i already saw working on my C64. With the Pet at least it is starting the Motor when using "LOAD" command and pressing ENTER. But then it is writing a 10 line Basic Program forever and dont stop. Soon or later i will figure this out..

    System after Booting.jpg
    System after Booting 2.jpg

  4. #144
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    Neat! Well done.

    For the cassette I would check the VIA (UC5) or the PIA (UC7).

    There’s not really much to go wrong - unless a timer/counter is not working properly.

    Have you checked that BASIC is keeping the right time?

    Dave

  5. #145

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    Quote Originally Posted by daver2 View Post

    Have you checked that BASIC is keeping the right time?

    Dave
    How can I do that?

  6. #146
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    Quote Originally Posted by miata View Post
    How can I do that?
    Set the time of day as follows:
    time$ = "HHMMSS"

    Then what a minute and enter
    ? time$

    For the graphics keyboards, the it may be that TIMER$ is the correct variable. Lower case timer$ for business keyboard.
    Last edited by dave_m; March 17th, 2020 at 05:08 PM. Reason: normal graphic keyboard

  7. #147
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    Swap C6 and C7 and see if you can write a program.

    Since the PET detects that the Play button is depressed, I would think that the cassette jumpers are correctly set so that should not be the problem. As daver2 says it is probably the PIA C7 or perhaps the VIA C5.

  8. #148

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    Quote Originally Posted by dave_m View Post
    Set the time of day as follows:
    time$ = "HHMMSS"

    Then what a minute and enter
    ? time$

    For the graphics keyboards, the it may be that TIMER$ is the correct variable. Lower case timer$ for business keyboard.
    Thank you, Dave. This works for me. I set up the time and wrote a little program displaying the current time on the left top of the screen. It maintains the time accurate!

    Hey - now i know for what i can use that thing. A nice looking Retro Watch for my Living Room. Letīs see what my girlfriend is thinking about this idea

  9. #149

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    Quote Originally Posted by dave_m View Post
    Swap C6 and C7 and see if you can write a program.

    Since the PET detects that the Play button is depressed, I would think that the cassette jumpers are correctly set so that should not be the problem. As daver2 says it is probably the PIA C7 or perhaps the VIA C5.
    I swapped C6 and C7 - same result. I can write a program but not write to Tape. It detects when pressing the play/record buttons but will never finish writing nor finish searching when try to read from Tape.

    Tape Write Test.jpg
    Itape read test.jpg

  10. #150
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    >>> Letīs see what my girlfriend is thinking about this idea

    Hmm, I can tell you what my wife would think about that idea if you like!

    I will checkout the source code for the BASIC SAVE routine.

    One thought, do you see any activity on the PIA pin connected to the cassette WRITE DATA output pin?

    Dave

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