How Can We Help?
The problem with this set is the field hold. The picture can
be locked only with the hold control towards one end of its
travel, and as the PL508 field output valve ages there is no
longer any adjustment available. Replacing the PL508
cures the trouble, but as this is required every couple of
months it cannot be the sole answer to the problem – which
has been present since the set was new. Initially a
replacement timebase panel was fitted, but the situation did
The sync separator transistor TR109 (BC117), though
not its collector circuit components, is on the i.f. panel. We
suggest you replace the transistor and check the value of
the upper resistor in its base bias network (R131 1MQ).
Then if necessary replace the field pulse integrating
capacitor C514 (0.005µF) and coupling capacitor C513
(300pF) on the timebase panel. Make sure that the PL508’s
cathode components are in order – this should include
C600 (250firF) on the convergence board.