elson at pico-systems.com
Sat Apr 29 10:50:04 CDT 2017
On 04/29/2017 08:34 AM, Aaron Jackson via cctalk wrote:
> The heater and control pins appear to be giving sensible voltages. The
> logic of the board is fine, I can type on the terminals keyboard and I
> get the correct characters on the other end of the serial cable. The PSU
> is putting out 31v which seems fine?
> I'm used to discharging the tube before fixing things inside CRTs
> (usually I only attempt to fix simple things like a broken toggle
> switch), but I have not managed to get a spark off this monitor. The
> tube doesn't seem to get charged up at all.
If everything is working, even a small monochrome monitor
should give a bit of a crackle (might have to listen closely
in a quiet place) and you should be able to feel the
electrostatic field on the hairs on the back of your hand
for a few seconds after powering on.
> I've measured the
> capacitance of nearly all caps and they seem fine, diodes seem to be
> working fine. Does this mean it is most likely the flyback transformer?
Since it doesn't smoke, I'm thinking the horizontal sweep
transistor may have gone out. It may have shorted, which
then may have burned up the primary winding in the flyback
(if left on long enough). I'd check that transistor for a
short, and then you can trace a few traces to identify the
primary terminals on the flyback and see if they are an open
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