MK1 will not power on - flashing power light

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Don't Panic. Please wash hands.

    Hello all - I pulled my Reloaded 64 out of the box after it had been stored for a couple of years. I powered it up with the same power supply I've always used (12v 2a) - and I get no screen output - just the power light blinking. (It resides in a 64C case.)


    I tried the scrape method on all of the ZIF sockets, re-seated all socketed chips. No fix unfortunately. I pulled the chips and tested them in my sixtyclone and they work fine.

    I have it setup for NTSC with a 6581. Power supply tests good at 12v 2a.

    Not sure what to check next?


    Thanks

    Are you sure that this is an original MK1? If the Power LED blinks on MK1, there's some serious space-time-bending going on (it's hardwired to the Vcc rail through a resistor).


    Jens

    It doesn't have dual sid support and does not look like the MK2. So it must be an MK1 - and the power light that is blinking is the one from the case. The LED attached by cable to the board. No video - power light on the case just blinks slowly.


    Code
    1. https://ilesj.wordpress.com/2015/05/24/c64-reloaded-first-impressions/

    Just tried turning it on again today and now there is no power light at all. Tried another power supply 12v 2.5a and same result - no power light and no video. Are there some test points on the board I can check for voltage? And yes the power supplies are center pin positive.


    Thanks.

    Thank you.


    Ok looked up the pin outs for each chip - no 5v anywhere. Checked the power supplies again - they're good. Took the board out of the case and flipped it over. Checked for 5v at the barrel connector for the power supply. Nothing - no 5v. Something is shorted somewhere.


    Disconnected the power supply. Oddly (unless this is normal which it doesn't seem it would be to me) there is continuity between all 3 pins on the barrel connector. So something is shorting the positive and negative together.


    Where should I look next?

    Quote from sncboom2k

    Checked for 5v at the barrel connector for the power supply.

    You should find 12V there.


    This looks like the protection diode shorted out - this happens if the polarity is wrong. Can you take pictures of the type stickers of all power supplies you've tried?


    Jens

    Sorry yes you are correct - I should have been looking for 12v at the connector. My brain was concentrating on the VCC for the IC's. I tested both power supplies - they provide12v on the center pin. The same ones I've been using for years. I'll test that diode with my meter later today as well as get you those pictures. Thanks.

    Ok - tested the D8 diode and it shows shorted. Definitely allowing voltage through both directions. I've ordered some and will replace it and report back. Thanks for the info Jens. As for the power supplies - both show 12v 2a with + on the center pin. Regardless - I've pitched the older of the two. If you have a part # for a supply you recommend, please share and I can order one of those as well.

    Thanks!

    I read in another post here that you said the diode could be removed (hence no protection) and the board should work. So I removed it and the board does now in fact work. I'll not use it until the new diode's arrive and I have installed it. Thanks again.