28 Aug
2014
28 Aug
'14
3:08 p.m.
On 28/08/2014 21:15, Sean Caron wrote:
I'm going to have to crack one myself pretty soon;
I got my VT131 out of
long term storage a few months back and tried to fire it up a few days
ago... Screen comes up, I get a flashing garbage character in place of the
block or underscore and terminal is unresponsive. The logic looks cursorily
OK and I hear that squeal that's somewhat suggestive of bad caps so I'm
going to have to take a look at the power section one of these days...
Unfortunately I can't cite mine as a working example for reference at this
point in time :|
I've replaced almost all of the capacitors on the monitor board and in
the power supply. It made quite a big difference because the vertical
linearity is now perfect on both terminals and I didn't even have to
adjust any pots. Before it was way out.
One logic board needed a new character generator and is now fully
working, the other one needed a new CPU but still has some other
problems. It will only work for about 10 seconds then either the video
signal disappears or the screen fills with random characters.
I can't really do any more debugging at the moment though because I
don't like to leave the power supplies on for too long due to the
aforementioned issue of resistors getting hot (which may or may not be a
problem).
Matt