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Thread: PET 8032 Resurrection Help!

  1. #1
    Join Date
    Mar 2012
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    Default PET 8032 Resurrection Help!

    Hello friends,

    I have seen many threads over the years where great men and women such as yourselves work in camaraderie to help with a sick PET. Well, I have one I'd like to get working for the holidays!

    It's an 8032 with 8032030, so I was disappointed I could not use the new board to switch this to an 80-column PET. Is it not possible at all, or just not easy?

    Anyway, here is where I am with it.

    Background:

    1) It worked in about 1990. It has been in storage since then in pretty good conditions, but I do live in very humid Georgia (USA).

    2) The inside does not look too bad, nothing living in it, no heavy corrosion that I can see. All the wires are connected still.

    3) When powered on, it chirps immediately (the good PET startup chirp) but nothing ever happens after that. The monitor never turns on, and the computer does not work "blind". i.e., it does not beep when holding the space bar.

    4) All the voltages seem to be there. It has 5v at the TTL chips, some 12v here and there. The wires going up to the monitor seem to have 22vac.

    5) It has two boards, with the top board (PET 64K MEMORY) connected to the bottom via the CPU socket. Just for testing, I removed this cable and put the 6502 in the socket. It powers up and chirps just like before, but still no video or full boot.

    6) I took some pics of it. There is a chip missing out of a socket in UD12, but that had to be like that back when it worked? I don't recall removing it...

    7) What are the next steps? I know the monitor will not turn on if the video chip is not initialized, correct?
    Attached Images Attached Images
    Last edited by rittwage; December 19th, 2018 at 05:00 PM.

  2. #2
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    A photo of the 64k board. All I could find is this board is normally in an 8296?
    Attached Images Attached Images

  3. #3

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    I have a dead one sitting on my bench at the moment, the logic board may be toast due so some open regulators but I have been nosing around the display board trying to ascertain if it is functional enough to run from a RasPi. Mine seems to fire up ok without input, I have heater voltage and power across the board where it should be, but I don't have a scope on hand at the moment to verify the vert/horizontal sections are firing up. Do you see the heater lighting up at least? Do you have a scope to do signal testing on the CRT board? Page 41 onwards of this document has some trace and alignment information to help you if so. As always be careful nosing around on a live CRT board, the flyback cord can bite you hard as can the filter capacitors unless discharged after shut down.

    As far as I know UD11 and UD12 are optional slots for adding your own programs, they are not required for the beastie to function.
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  4. #4
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    Quote Originally Posted by ATSystems View Post
    I have a dead one sitting on my bench at the moment, the logic board may be toast due so some open regulators but I have been nosing around the display board trying to ascertain if it is functional enough to run from a RasPi. Mine seems to fire up ok without input, I have heater voltage and power across the board where it should be, but I don't have a scope on hand at the moment to verify the vert/horizontal sections are firing up. Do you see the heater lighting up at least? Do you have a scope to do signal testing on the CRT board? Page 41 onwards of this document has some trace and alignment information to help you if so. As always be careful nosing around on a live CRT board, the flyback cord can bite you hard as can the filter capacitors unless discharged after shut down.

    As far as I know UD11 and UD12 are optional slots for adding your own programs, they are not required for the beastie to function.
    The heater on this monitor is back inside of a plastic housing that screws onto the back of the computer. Unfortunately, I cannot see it because of that. I removed the screws, but it only comes off on the inside. I will have to disassemble the top of the computer to check that. I do own a scope, but would need help operating it and finding the proper settings. I could then check the signals going on up to the display...

    The computer is not booting all the way up, so I suspect I have bad ROM and/or RAM, and they are all unsocketed, so that will be fun. However, since it does the same thing with the 64k board as without, would that mean that RAM may be good (less likely both main RAM and aux RAM are bad) and I have a bad ROM? Hmmm... I wonder if they expansion board completely replaces the original RAM, disabling it?
    Last edited by rittwage; December 19th, 2018 at 06:40 PM.

  5. #5

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    Quote Originally Posted by rittwage View Post
    The heater on this monitor is back inside of a plastic housing that screws onto the back of the computer. Unfortunately, I cannot see it because of that.
    Indeed it is, but you can see the heater if you look in sideways from where the arrow indicates.

    Quote Originally Posted by rittwage View Post
    I removed the screws, but it only comes off on the inside.
    These screws? The whole lid should lift up and off once they are removed, it might be a little stuck due to being in the same spot for years but don't be afraid to apply a little muscle.

    20181220_133618.jpg

    Quote Originally Posted by rittwage View Post
    I do own a scope, but would need help operating it and finding the proper settings.
    Wise to be cautious but the sample wave forms included in the document give you your scope settings in the upper top left and right of each diagram. If you are not sure how to translate these to your scope then yeah, you might want to have a look at some instructional videos on how to set up a scope and your probes for testing.

    I'm not so good on digital troubleshooting yet, but I'm sure a wizard will descend and give you some advice on the mainboard soon enough. I would guess as it is making its happy noise that the RAM/ROM is passing its tests but there might be an issue on the output side of the CRTC circuitry. Or you have a dead display
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  6. #6
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    Quote Originally Posted by rittwage View Post

    3) When powered on, it chirps immediately (the good PET startup chirp) but nothing ever happens after that. The monitor never turns on, and the computer does not work "blind". i.e., it does not beep when holding the space bar.
    The chirp is good. It means the board can run a first few instructions before going south. The CRT need high voltage that comes from the using the Horizontal Sync (20 KHz) as a chopper frequency source. So apparently the CRT controller (6545) is not being initialized.

    Holding down the space bar will not get it to repeat spaces. You must pulse the key 40+ times.

    You need daver2's Pettest3 programed into a 2532 EPROM, and place it in the UD7 Editor socket. This may give us vital some information on the RAM and ROM. If that passes, it goes on to test the keyboard. We know, since you get the chirp, that the machine gets to the Editor ROM OK.

    If you don't have a PROM Burner, send me you mailing address my private message, and I will mail you a programmed EPROM. We'll do almost anything here to get a PET back on the air.
    -Dave

  7. #7
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    Quote Originally Posted by dave_m View Post
    The chirp is good. It means the board can run a first few instructions before going south. The CRT need high voltage that comes from the using the Horizontal Sync (20 KHz) as a chopper frequency source. So apparently the CRT controller (6545) is not being initialized.

    Holding down the space bar will not get it to repeat spaces. You must pulse the key 40+ times.

    You need daver2's Pettest3 programed into a 2532 EPROM, and place it in the UD7 Editor socket. This may give us vital some information on the RAM and ROM. If that passes, it goes on to test the keyboard. We know, since you get the chirp, that the machine gets to the Editor ROM OK.

    If you don't have a PROM Burner, send me you mailing address my private message, and I will mail you a programmed EPROM. We'll do almost anything here to get a PET back on the air.
    -Dave
    Thanks Dave- I think I have an adapter from 27cXXX 28-pin to 25xx series 24-pin. If this will work as it does in the C64, I should be able to get it working, and that ROM is socketed. I will find the PETTest ROM and see if I can get it to boot.

  8. #8
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    Where can I find daver2's Pettest3? The 8032 test rom I found on Zimmers is a kernal replacement...
    Last edited by rittwage; December 20th, 2018 at 07:25 AM.

  9. #9
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    Under here!

    https://drive.google.com/open?id=1Q2...Bqa231ZXItOQWP

    Look for V03 beta.

    Any questions ask the author - me !

    I am about to make some changes over the holiday time to (hopefully) finish this job off...

    It will have a full memory test (already in and working - just a poor user interface) and a screen for setting up the monitor (already in - just no way to invoke it). I think dave_m wanted something to 'beep' the sounder - so I shall add that feature and then see how much space I have left in the 2K EPROM.

    I am also going to 'swap around' the order of some of the page 0 and 1 RAM tests.

    Dave
    Last edited by daver2; December 20th, 2018 at 09:42 AM.

  10. #10
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    Looking at your ROM set - it is not that you have a device missing from UD12 ($9xxx) - you have gained an extra device at UD11 ($Axxx) - the one with the white dot! I wonder what that is?

    Can you identify what is actually marked on each and every ROM you have in the machine and we may/should be able to identify what is actually in there.

    Dave

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