COSSOR CT1973A

The sound comes on almost immediately after the set has
been switched on but there is a long delay before the picture
appears. It’s clear, but then starts to shrink at the top and
bottom – the width remains o.k. Altering the setting of the
height control makes no difference. The height can be
temporarily regained by advancing the contrast and
brilliance controls, but the picture then explodes and
disappears. I’ve changed the field timebase valves without
success.
The long delay in the picture appearing is probably due
to the fact that the PL36 line output valve is in need of
replacement. The fact that the picture size varies as the c.r.t.
beam current increases means that the e.h.t. regulation is
poor. So change the EY86 e.h.t. rectifier. To get the height
right check the 1.21\452 resistor (R438) in series with the
height control – you’ll undoubtedly find it has increased in
value. (Philips 152A series.)