3 Sep
2012
3 Sep
'12
2:03 p.m.
[+5V supply line]
No, it stays positive. Just a lot of ripple (between
2 and 5V).
In which case it's unlikely to have done any damage.
Hopefully it's as simple as replacing the filter
capacitor. The power
First look at the ripple freqeuncy. Just about all classic cumputers used
full wave rectification, so you'd epxrpct it to be twice the mains
frequency of the rectifiers are OK.
I would be 99% sure the problem was cpaacitor-related. I can't think of
another common cuuse for excessive ripple.
supply in this thing looks like it's going to be
fun to pull out :).
Some machines are easy to work on, some are hard :-(. And soem claim to
be easy to repair, but are actually very hard to work on. Those are the
ones where swapping modules is trivial, but actually getting a module to
be operational outside the machine so you can test it with a 'scope is
non-triival. I recall the time I had to trace a logic fault on a DEC
Rainbow. Ended up with the PSU running upside-down half off the edge of
the bench...
-tony