Powering Apple Cassette Interface with +5 volts only - should be no need for -12volt (ATX) supply

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Joined: Jun 5 2008
Posts: 383


After some offline discussions about powering an ACI with only +5 volts with Cory, I did some thinking and came to the conclusion that -12 volts is probably not needed. I did an experiment with my ACI last night connecting the -12 volt supply of the LM311 comparator to ground instead of -12 volts. It worked fine with both real cassette and ipod input. To do this, just lift pin 4 of the LM311 and jumper to a nearby ground. One nearby ground location is pin 7 of the 74LS74. Once this is done, -12 volts is not connected to anything on the ACI and is not needed. My tests were on a Mimeo, but I don't think operation on a Replica 1 should be any different.

MIke Willegal

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Joined: Oct 9 2011
Posts: 1075
Re: Powering Apple Cassette Interface with +5 volts only - ...

Awesome so Replica-1 owners can use the ACI and a cheap wall wart instead of an ATX power supply. They should be able to make a simple jumper wire on the Replica-1 board and leave the ACI as is!!!!

Great work Mike.


qubitz's picture
Joined: Oct 24 2008
Posts: 26
Re: Powering Apple Cassette Interface with +5 volts only - ...

Sweet, I'm going to give this a try tonight...I always hated lugging a ATX power supply around.