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Thread: VIC 20 Black Screen Diagnosis

  1. #41

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    Quote Originally Posted by VERAULT View Post
    come on, in the end you still got a working VIC-20 at a good price. Add some heatsinks and buy a new vic 20 ultimem card and tell me if its worth buying (by the guinea pig) http://store.go4retro.com/ultimem-vi...ion-cartridge/
    Do you have any recommendations on which heat sinks and how to attach them?

  2. #42

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    I actually had to repair the RF modulator too in order to get decent output from it, but that just consisted of replacing a couple of 10uF electrolytic capacitors that had gone bad.

    That turned out to be a remarkably clear picture for RF.

    IMG_20180128_143419.jpg

  3. #43
    Join Date
    Jan 2012
    Location
    Connecticut, USA
    Posts
    2,106

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    Quote Originally Posted by jmetal88 View Post
    I actually had to repair the RF modulator too in order to get decent output from it, but that just consisted of replacing a couple of 10uF electrolytic capacitors that had gone bad.

    That turned out to be a remarkably clear picture for RF.

    IMG_20180128_143419.jpg
    looks good do you intend to use it on a tv? I honestly cant stand the rf signal on my eyes anymore.
    for heatsinks listen to rays recommendations (he told me to remove the rf cage shield (top) since its too thick and traps in heat. I honestly just used heatsink plaster and put heatsinks on everything. Figure couldnt hurt, and if it lets them work even longer all the better.

    I bought these:https://www.ebay.com/itm/20PCS-NEW-H...72.m2749.l2649
    but they are TOO small in my opinion, youd need 3 or 4 just on the cpu. Im in the market to buy more
    These are all over ebay, https://www.ebay.com/itm/4x-Heatsink...cAAOSw9idZ9MBT
    kinda pricey, id rather just buy a pile of them and use as I need them.

    Maybe someone else on here can give some input.

  4. #44

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    Quote Originally Posted by jmetal88 View Post
    Alright, I basically did a whole bunch of de-soldering that I didn't have to. Removing UAB1 didn't affect the situation at all, so I started going through the logic chips. Found another bad one (I discovered that my EPROM programmer can test logic chips, and that saved a lot of time), this time a 74LS245 (UD8 ). And it was already socketed (if only I had tested all of those first). Replaced it, got a picture. Now to put everything back together and see if I have the other functions working.
    Hey, I am having exactly the same issue as you and before i drop a fair bit of cash on a new Kernal I am thinking trying these 74LS245's might be worth it. My vic20 (cr version) a DM74LS245N in UD8 and M74LS245P in UE8. Havin a look around the net I am just wondering if you can confirm that any chip listed as 74LS245 would be compatible?

    These for example:

    https://www.rapidonline.com/Texas-Instruments-SN74LS245N-Octal-Tristate-Bus-Transceiver-83-0676?IncVat=1&pdg=pla-336930985820:kwd-336930985820:cmp-757438067:adg-44804851896:crv-207912323492id-83-0676:dev-c&gclid=Cj0KCQiAkfriBRD1ARIsAASKsQI28gAIULR-hoUP467Sj70UO_-7lDfRUzCTo7A7HdrfgKX6pFHwQXsaAmKsEALw_wcB

  5. #45

    Default another VIC20 black screen!

    Hello,
    I am trying to revive my old vic20 I got from early 80s and has remained switched off for the past 35+ years.
    The problem is a complete black screen. There's a signal over the video cable (DIN to SCART cable) as the TV where I plug it in recognizes there's "something". But it stays black.

    Tests I have done so far:

    - The power supply is working, as I tested it on both 5V DC and 9V AC.
    - All main ICs get the 5V DC and feel warm/hot after some minutes.
    - Trying to blindly SHIFT + RUNSTOP with an original Commodore C2N tape connected does not have any efffect: the tape motor does not start, though I could measure a 5V DC on the tape connector too.
    - Tried to reset all the socketed ICs (only VIC and KERNAL)
    - Desoldered UAB1 (1st VIA) and tried without it
    - Soldered a socket to reseat the UAB1

    I could go on and socket also the 2nd VIA and the two RAM chips, but I feel I wouldn't get much farther.

    Any hint from you guys? I do not have an oscilloscope that would allow to understand if there's a fried IC.
    Isn't there any harness I could get somewhere that would bypass the VIC and generate a video signal and run some diagnostic SW?

    thanks for your help

  6. #46
    Join Date
    Dec 2012
    Location
    São Paulo country, Brazil
    Posts
    728

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    Quote Originally Posted by jmetal88 View Post
    Do you have any recommendations on which heat sinks and how to attach them?
    I use to remove the heat sinks from burnt PC boards (the small heat sink on the bios, etc.), cut them to fit the IC size, put some thermal paste in the middle and glue it with a two-component glue. Not beautiful, but cheap an funcional.
    Remember to write somewhere on the IC (i.e. behind it) the IC model, or you will have a lots of IC with heat sink and no IC code.

    --Giovi

  7. #47
    Join Date
    Dec 2012
    Location
    São Paulo country, Brazil
    Posts
    728

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    Quote Originally Posted by jmetal88 View Post
    I actually had to repair the RF modulator too in order to get decent output from it, but that just consisted of replacing a couple of 10uF electrolytic capacitors that had gone bad.

    That turned out to be a remarkably clear picture for RF.

    IMG_20180128_143419.jpg
    With a very little and simple change on the PCB, you can get an S-Video signal from you VIC-20; I did it in one of mine, it gives a really sharp and stable image.

  8. #48
    Join Date
    Dec 2012
    Location
    São Paulo country, Brazil
    Posts
    728

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    Quote Originally Posted by mrseylok View Post
    Hello,
    I am trying to revive my old vic20 I got from early 80s and has remained switched off for the past 35+ years.
    The problem is a complete black screen. There's a signal over the video cable (DIN to SCART cable) as the TV where I plug it in recognizes there's "something". But it stays black.

    Tests I have done so far:

    - The power supply is working, as I tested it on both 5V DC and 9V AC.
    - All main ICs get the 5V DC and feel warm/hot after some minutes.
    - Trying to blindly SHIFT + RUNSTOP with an original Commodore C2N tape connected does not have any efffect: the tape motor does not start, though I could measure a 5V DC on the tape connector too.
    - Tried to reset all the socketed ICs (only VIC and KERNAL)
    - Desoldered UAB1 (1st VIA) and tried without it
    - Soldered a socket to reseat the UAB1

    I could go on and socket also the 2nd VIA and the two RAM chips, but I feel I wouldn't get much farther.

    Any hint from you guys? I do not have an oscilloscope that would allow to understand if there's a fried IC.
    Isn't there any harness I could get somewhere that would bypass the VIC and generate a video signal and run some diagnostic SW?

    thanks for your help
    Hi...
    you should make a new thread, or it will be really hard to answer to two different people on a similar problem.

    However in my (little) experience fixing vic-20, the most probable culprit would be the kernal, that can be replaced with an eprom or flash rom (but you need good unsolder and solder skills and an eprom programmer).
    As far as I know there's no replacement for VIC chip, and you need it working, no way.

    However here there's a lot of people that can help you, if you will open a new thread, but you will need at least a multimeter and a probe.

    --Giovi

  9. #49

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    Quote Originally Posted by giobbi View Post
    Hi...
    you should make a new thread, or it will be really hard to answer to two different people on a similar problem.

    However in my (little) experience fixing vic-20, the most probable culprit would be the kernal, that can be replaced with an eprom or flash rom (but you need good unsolder and solder skills and an eprom programmer).
    As far as I know there's no replacement for VIC chip, and you need it working, no way.

    However here there's a lot of people that can help you, if you will open a new thread, but you will need at least a multimeter and a probe.

    --Giovi
    Ok, thank you. I will follow your suggestion and open a new thread!

    --mrseylok

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