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Thread: PET 2001-32N - Diag works in UD9, but with Kernal it fails to start

  1. #111

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    Quote Originally Posted by iz8dwf View Post
    Onboard regulators can only have issues if the electrolytic capacitors are dried out. I just suggested you to check the power supply with the oscilloscope in AC coupling (I should have been more precise in my suggestion, sorry). Leave the original power supply and try to see if UC7 has proper ground connection and PIN 9 has no measurable continuity with nearby pins maybe. Check +5V and GND pins of UC7 when the problem starts with AC coupling on the oscilloscope... there must be something wrong around there.

    Frank
    Well, all of the electrolytics were already replaced. Since I've already wired in a switching power supply to feed the regulators, I'm going to leave it in place for now since the system operates in the same way and it allows me to take the enormous PET chassis off of my workbench.

    I don't see anything really obvious going on in UC7, but I absolutely see something that looks very much like that signal coming off of UC9 on pins 14 and 15. Going back to the schematics to figure out what that is.

  2. #112

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    Oops... and I'm on hold until November because I just accidentally killed the 74145 in UC9 when my probe slipped.

    In other news, after killing the chip, I removed it.. and it has absolutely no impact on my issue, even though it's connected to the PIA on pins2 through 5 and exhibits the signal that I see leaking over.

  3. #113
    Join Date
    Feb 2009
    Location
    Southern California, USA
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    2,692

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    Quote Originally Posted by dhoelzer View Post
    Oops... and I'm on hold until November because I just accidentally killed the 74145 in UC9 when my probe slipped.

    In other news, after killing the chip, I removed it.. and it has absolutely no impact on my issue, even though it's connected to the PIA on pins2 through 5 and exhibits the signal that I see leaking over.
    The PIA C7 may be bad.

  4. #114
    Join Date
    Jun 2012
    Location
    UK - Worcester
    Posts
    3,155

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    Hi Dave,

    I am still catching up with all the posts since I have been away on business, but the OP has tried multiple PIAs (some of which are - supposedly - known good) and the PET does the same thing... I suggested bending the CB1 (?) pin out to see if the problem was being generated from the outside.

    So, having quickly read the posts it is occurring outside of CB1; but there appears to be a whole host of issues now occurring . I need to read a bit more closely...

    Which version of PETTEST are you using out of interest? Mine or not?

    Dave
    Last edited by daver2; October 19th, 2019 at 02:13 AM.

  5. #115

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    Quote Originally Posted by daver2 View Post
    Hi Dave,

    I am still catching up with all the posts since I have been away on business, but the OP has tried multiple PIAs (some of which are - supposedly - known good) and the PET does the same thing... I suggested bending the CB1 (?) pin out to see if the problem was being generated from the outside.

    So, having quickly read the posts it is occurring outside of CB1; but there appears to be a whole host of issues now occurring . I need to read a bit more closely...

    Which version of PETTEST are you using out of interest? Mine or not?

    Dave
    Not yours at the moment. Just the standard Gs and character sets since I'm now pulling all RAM and EPROMs from a daughterboard.

    It's pretty frustrating because on Monday, the system was completely booting and I was able to write code since the IRQ issue was sporadic. Now the system is again completely unusable.

    Regarding the PIAs, yes, I have six known-good PIAs.

  6. #116

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    Quote Originally Posted by dhoelzer View Post
    Not yours at the moment. Just the standard Gs and character sets since I'm now pulling all RAM and EPROMs from a daughterboard.

    It's pretty frustrating because on Monday, the system was completely booting and I was able to write code since the IRQ issue was sporadic. Now the system is again completely unusable.

    Regarding the PIAs, yes, I have six known-good PIAs.
    I put your pettest in.. it fails to even clear the screen.

  7. #117
    Join Date
    Jun 2012
    Location
    UK - Worcester
    Posts
    3,155

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    Just checking the obvious...

    You have got the latest code?

    You have put the original kernal ROM back in?

    You have put my PETTEST in the correct type of 2K EPROM (2716)?

    You have put my PETTEST in place of the EDIT ROM?

    Just want to make sure...

    Dave

  8. #118

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    Quote Originally Posted by dhoelzer View Post
    Oops... and I'm on hold until November because I just accidentally killed the 74145 in UC9 when my probe slipped.

    In other news, after killing the chip, I removed it.. and it has absolutely no impact on my issue, even though it's connected to the PIA on pins2 through 5 and exhibits the signal that I see leaking over.
    I was wondering how you'd kill a 74145 with a probe? You'd have to hit one of the outputs with +5 or +12 or something.
    Dwight

  9. #119

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    Quote Originally Posted by daver2 View Post
    Just checking the obvious...

    You have got the latest code?

    You have put the original kernal ROM back in?

    You have put my PETTEST in the correct type of 2K EPROM (2716)?

    You have put my PETTEST in place of the EDIT ROM?

    Just want to make sure...

    Dave
    Yes to all. Things have significantly deteriorated at this point. The non-you Pettest now only activates portions of the screen with the rest remaining random junk, and that's after being powered off for 12 hours.

  10. #120

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    Quote Originally Posted by dhoelzer View Post
    Yes to all. Things have significantly deteriorated at this point. The non-you Pettest now only activates portions of the screen with the rest remaining random junk, and that's after being powered off for 12 hours.
    Let's just say it wasn't pretty and leave it at that. I also have a 2nd degree burn as a related part of the mishap, trying to catch my desoldering gun as it fell. It was a catastrophe without a cat being involved.

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