PYE 697 CHASSIS
There are field flyback lines on the screen. The blanking
circuit in the PL802’s cathode circuit has been checked to
no avail. Also the brightness keeps varying every minute or
so. The variations are less frequent when the set’s been on
for a few hours.
Field flyback lines will always be present to a little extent,
though careful adjustment of the field output stage bias
potentiometer RV24 should reduce them to a minimum.
Brightness variations are usually due to faulty edge
connectors, since half the brightness and beam limiter
circuits are on the front control panel and the remainder on
the line timebase board. Also check the 12.5µF reversible
electrolytic C201 on the front control panel if necessary,
and the clamp diode D39A.