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Thread: Who knows something about the old NEC PC-6001A around here?

  1. #81

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    Only had a little while to play with it today but found out that the wire going from CN606 on the power supply was not attached to anything. It looks like it can only go to CN12, but the schematics don't make it explicit that CN606 -> CN12.

    CN12 goes to pins 44 and 46 in the cartridge slot, which this Japanese site says seems to be related to hotswap protection for the cartridges:

    MSW1 and MSW2 are shorted on the extension board side. Inside the expansion slot, there is a power-off switch, and when this switch is turned on, the power supply of the power supply unit is stopped. In other words, when you try to insert the ROM cartridge into the PC-6001, the power-off switch is physically turned on. The PC-6001 is designed to stop electrically if you attempt to handle it as dangerous as inserting the ROM cartridge while the PC-6001 is operating. If only this is done, the PC-6001 will not operate, but if the MSW1 and MSW2 are shorted on the ROM cartridge side, power supply from the power supply unit is started even if the power-off switch is ON. is. If you insert something thin like a board into the extension terminal, the power-off switch will not turn ON (do not touch the switch), so there is no need to short MSW1 and MSW2.
    Although Google Translate has made it more confusing than I want it to be, I think it's saying MSW1 and MSW2 are there to override the reset microswitch in the cartridge slot?

  2. #82

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    It was indeed shorted caps - the tantalums on the 12V and the -12V rail, right next to the PSU connector to the mainboard, were a zero-ohm dead short.

    Lucky for me, the RAM appears to be OK so far - I was able to get to the "How Many Pages?" screen.

    Unfortunately, the RETURN key doesn't seem to work (so I can't say how many pages) - I'm going to try cleaning it and then I guess see if there's some internal damage to the keyboard. The letter, number and shift keys seem to work.

    Thanks for the help! Looking forward to trying this thing out once the keyboard is touched up.

  3. #83

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    Good job finding that. You can try CTRL-M and see if it will accept that is return.

  4. #84

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    That worked great! I wish I had thought of that. Thanks a lot.

    I'll do some keyboard cleanup in the next few weeks and hopefully that will make this machine fully usable again!

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