P3 - Reverse engineering

  • Greetings,

    A few days ago I started to desolder the P3's CPU board (CAAA08 - CA1102/8HP00067). The desoldering hand pump broke soon afterwards and this Monday received a replacement (which broke after 1h of use, but that's another story :D). Approximately 2/3 of the board has been exposed and the silk screens containing the components is visible in the unearthened region.

    Both resistors and capacitors use the standard references (Rn, Cn; n being a number).

    Resistor arrays use "N24/x" (x being a number).

    Crystals use "QUn" (n being a number).

    Integrated circuits, on the other hand, have a unique reference consisting of a single number and are also labelled with (what I think it is) their TA's part catalog identifier:

    Silk Screen ReferenceIntegrated Circuit Reference

    EPROMs in this board don't seem to have a catalog reference.

    I hope to be able to complete this list soon, and to start real work with the board - so we can get a proper schematic to repair it and also to identify parts of the bank-switching mechanism.



    When I tried to list all retro systems I have at home, the "The message is too long, must be under 500 characters" error appears! :lol:

  • Thanks Jaume;

    You chose a tedious job.

    It is a pity that we really do not have circuit diagrams of the TA Triumph Adler / sks of the Px machines of the plug-in cards.

    I still have a sks-KISS CPU card - which I successfully tested in a P2U. But I had to change the MOS part (KEybord) EPROM to start in TA P2 and work with it.

    A friend had made a HARDPATCH on this KISS CPU around 1981. Use a switch (normal - no BANKING) and SPECIAL as banking via PORT 78h (as with TA P2 / P3).

    Clearly, unfortunately, no sketches - but there are a number of IC piggyback and various thread wire connections.

    I hope to forograph the map soon and to identify the lines.

    Possibly. you can create a great base with or other USER.

    So good luck and see you soon.

    Kind regards


  • You chose a tedious job.

    Fortunately the worst part is nearly finished... albeit the connector will prove to be a nightmare. ;)

    At this point six ICs, two resistors, four resistor arrays, four capacitors, a socket and the connector remain soldered. Three new values have been added to the previous list:

    Silk Screen ReferenceIntegrated Circuit Reference

    I'll continue disassembly tomorrow. With a bit of luck I may be able to leave it flat by then.



    When I tried to list all retro systems I have at home, the "The message is too long, must be under 500 characters" error appears! :lol:

  • Hi Jaume,

    Quote from jlopez

    A few days ago I started to desolder the P3's CPU board

    did I understood well, that you put off all components of the PCB to get an empty board? Then you want to draw a circuit diagram of the board?

    In the 1990s a colleague and I did a similar job, but we did not destroy the original Z80-interface-board. He checked the circuits on the board with an ohm-meter. So we got a big chart with all connections of the components. I disassembled the EPROM. So we could redesign a new board with similar functions.

    If you have really an empty board (hopefully it is only double sided and not a multi layer), you can scan it with a flat bed scanner on both sides. Then you can try to colorize the sides in different colours and make them semi transparent. Then you can overlay them to get a good overview.

    I think it will be a lot of work, but you will get a good documentation for your system.

    I wish you good luck!

    Kind regards


  • Removing them all was a must, certain components can interfere multimeter readings (low impedance resistors, dead capacitors, etc.). And yes, I was going the scanner way (scanners don't have either lightning or perspective problems). You read my mind. :S

    Just for the record, months ago I had the backplane documented, but I don't remember where did I post it... Those documents may belong to this thread now and for this reason I'm uploading them here too.

    Thank you very much,