8 Dec
2009
8 Dec
'09
8:16 p.m.
On Dec 8, 2009, at 11:35 AM, ard at p850ug1.demon.co.uk (Tony Duell) wrote:
Ah, sorry. Don't know what I was thinking not including that :).
It's a CDC 721 (with PLATO mods). So obviously I'd like to get it
working smoothly...
With the top cover off I can get a pretty good view of all of that,
though the flyback itself is a little hard to see. In a pitch black
room I wasn't able to see anything unusual.
Picked up an old terminal in very nice cosmetic condition; it works
fine
Make/model? Just in case one of us has heard of it and knows any stock
faults. barring a bit of visual "jitter" on the
display -- not sure how
best to
describe it. The picture is clear and sharp but occasionally a few
scanlines will spike off to the right a bit. Coinciding with this
spiking are tiny crackling noises from inside the monitor. (Or at
least
it seems like they coincide, obviously I can't verify this.)
I thought it might be HV leakage based on discussions I've seen on
this
THis does intiially sound like HV leakage. The spike produced when
something breaks down could well upset the horizontal scan cirucitry
too.
Where have you been looking for signs of this? I'd certainly look at
the
flyback transfortmer, the CRT anode capp, the CRT earthing contacts
(to
the outside aquadag coating on the flare), on the CRT base PCB (the
EHT
is not he only voltage that can flash over, there could well be a few
hundred volts on a CRT base pin) and so on.
Have you examined the solder side of the monitor PCB with the power
on? A
cracked solder joint can produce some intereting sparks.
I'll check that tonight.
Could it be internal breakdown of a capactior (e.g. the 3rd harmonic
tuninc capacitor on the flyback)?
You would know far better than I :)
Thanks (and thanks for all the other responses as well)
Josh
-tony