So, helping out someone with a 2 slot (MV2F). Original issue was a calendar error, apparently due to battery damage. The crystal was replaced before I got to the board.
I cut out the battery, removed the resistor in the charging circuit (470 ohm), and added a battery holder.
There was a corroded 22k ohm resistor near the battery that I replaced. Most of the legs on one side of the HC32 nearest the battery were also corroded, so replaced that as well. Jumped a broken trace from pin 13 on the HC32 to the 22k ohm resistor.
There is also a 10D1 Diode near the battery that is corroded and needs to be replaced. I believe that's part of the charging circuit, but not sure.
Right now it's booting to what looks like a garbled crosshatch screen, with nothing else. I'm unable to get into the work ram test or boot into a game.
So I'm thinking theres still something wrong near the battery, maybe with the crystal.
Here are my logic readings for the 4990 and HC32:
4490:
pin 1 - H pin 14 - H
pin 2 - H pin 13 - H
pin 3 - H pin 12 - H
pin 4 - L pin 11 - L
pin 5 - L pin 10 - L
pin 6 - L pin 9 - H
pin 7 - L pin 8 - L
HC32:
pin 1 - H pin 14 - H
pin 2 - H pin 13 - L
pin 3 - H pin 12 - L
pin 4 - H pin 11 - L
pin 5 - H pin 10 - H
pin 6 - H pin 9 - H
pin 7 - L pin 8 - H
Any suggestions on where to start?
I cut out the battery, removed the resistor in the charging circuit (470 ohm), and added a battery holder.
There was a corroded 22k ohm resistor near the battery that I replaced. Most of the legs on one side of the HC32 nearest the battery were also corroded, so replaced that as well. Jumped a broken trace from pin 13 on the HC32 to the 22k ohm resistor.
There is also a 10D1 Diode near the battery that is corroded and needs to be replaced. I believe that's part of the charging circuit, but not sure.
Right now it's booting to what looks like a garbled crosshatch screen, with nothing else. I'm unable to get into the work ram test or boot into a game.
So I'm thinking theres still something wrong near the battery, maybe with the crystal.
Here are my logic readings for the 4990 and HC32:
4490:
pin 1 - H pin 14 - H
pin 2 - H pin 13 - H
pin 3 - H pin 12 - H
pin 4 - L pin 11 - L
pin 5 - L pin 10 - L
pin 6 - L pin 9 - H
pin 7 - L pin 8 - L
HC32:
pin 1 - H pin 14 - H
pin 2 - H pin 13 - L
pin 3 - H pin 12 - L
pin 4 - H pin 11 - L
pin 5 - H pin 10 - H
pin 6 - H pin 9 - H
pin 7 - L pin 8 - H
Any suggestions on where to start?
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