Posted By
weidi
on 2021-12-20
10:01:53
|  Re: Cartridge port Not working correctly
Quick look at your measurements on U20 and:
1) I don't like pin 4 to 7 (first 2-to-4 line decoder outputs) voltage are above pin 16 - Vcc (4.82V)
- this is not normal and potential source of problems
Similar story with pin 9,10,11 (second 2-to-4 line decoder)
I have to look at the schematics for possible answers why that voltage is above Vcc
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