30 Jun
1999
30 Jun
'99
9:18 a.m.
I'm suspicious of one of the 7405s (Hex open-collector
inverters) driving the data lines to the MPU-A. I
don't have any replacements, but I do have a handfull
of 7406s (Hex open-collector high-voltage inverters).
The pinouts in the Chip Directory look the same, only
difference by them is that the 7406 is "Maximum output
voltage is 30V". I think I'll try socketing the
suspect chip (U1 for anybody keeping score) and putting
in a 7406.