16 May
2011
16 May
'11
2:09 p.m.
I'm not making a lot of progress, was using my time to fix the Citroen DS
replacing thegearbox in it and overhauling the steering cylinder and fixing
Ah, right... It's a lovely vehicle, but it needs a bit of work to keep
it going. I fully understand.
a lot of little items which you encounter when working
on a 44 year old car.
It's a little like classic computing, if you don't touch it everything keeps
working, but if ....etc.
Exactly.
Citroen used a rubber based wire insulation for the DS
and Pallas models
between 1965 and 1968.
This kind of insulation hardens over time and corrodes the copper wires, in
Ouch!
[...]
To come back to the HP 9830 I did find some time to
connect the LA to the
datapath board and look at the Carry and ALU signals
The carry doesn't change while the processor is running it's test cycle, the
QC and AC lines seems to be consistent to the processor state. So I think I
have to look at the timing of U12B and at the BCD mode X2.
It's not unhear-of for the 7474 that holds the 2 carry flags to fail. I
know I had to chaage it in one of my 9800s (I forget which one). Of
course with a logic analyser it's easy to see if the output should be
changing.
I'll get it running .. some day
I know the feeling...
-tony