Emergency repair on the P2 power supply

  • Hello,

    Five years ago my father and I found in a village of the province of Lleida (Catalonia) our first Alphatronic P2. Soon, problems regarding the power supply started to make an act of presence. The first day, the filter was blown. I can't remember exactly how much time passed but in a three months term the power supply was dead. In our case, the 5v module failed. As some of its components were popular only in West Germany we couldn't find direct replacement or information was missing so my father decided to innovate "a bit" and bypassed the +/-5V unit.

    The bypass adapter, the connector of the ATX can be seen over the left border of the floppy drive surface. The 5V unit is removed and contacts placed on thhe screws, which are used in the design to send power between both boards.

    Here connection to the P2 power supply can be seen with detail. Ground is common.

    A pair, random pictures showing the connector of the ATX power supply with the adapter connected.

    We use an old ATX power supply (those with a switch), but if there isn't any available a modern one (those with push button) can also be used. Prior to that we used one of those and if you do, remember that, in order to start it you need to connect the contact of the green wire in the main connector of the PSU with any ground contact on the came connector.

    This does not fix your power supply, but allows the computer to turn on. I consider it an emergency repair and should not be considered a proper solution. It is very helpful, however.

    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:

  • Partial circuit diagram of the + 5V unit

    Only a short time ago, I have seen in a forum post - unfortunately only partial circuit diagrams for a TA + 5V module. The author had apparently been working with Alphatronic P2x devices / service or at that time been a TA dealer.

    And apparently the USER still possesses various hardware documents to the P2 systems.

    So far, the USER (from Heidelberg) is almost not in the FORUM to some inquiries. Pity!

    What I have found to the power adapter TA P2 - I have already written in the forum.

    There is a PDF file - as LINK! ( I hope the Link work? )

    I will still look for the USER from Heidelberg to the other TA P2 documents - I hope I find that?

    I think the network modules are certainly revised several times by TA,

    so that not always this plan with e.g. a real network module will be.

    But you should be able to find the basic principles again.

  • easy and genial

    Hello Jaume,

    I once looked at the photos closer to the cable connections.

    A pair, random pictures showing the connector of the ATX power supply with the adapter connected.

    That looks easy and genieal.

    Is the intervention on the + 5V (TA module) so correct?

    a) the upper +5 control card was simply removed;

    b) Only +5 V (black wire) and 0V (red / brown wire) are screwed on the bolts (TA rest modul) by the AT PSU.

    c) from the AT PSU earth (grond) yellow / green also has to be connected to the P2.

    Is the background right?

    I can see that the AC voltage from the transformer supplied to the narrow PSU, so the + 12V and -12 are generated. Therefore, the transformer must remain over the header. And the external + 5V is also distributed to the mother card.

    What else was changed with the pins (to motherboard)?

    Or is there more to be done?