THORN 1500 CHASSIS
There is patterning over the whole screen area on all
channels – not too bad, but enough to be distracting. Also,
when changing channels channel two cannot be obtained –
no sound or vision. The tuner assembly has been checked
but I can find no mechanical reason for this. The only clue I
can offer is that on two occasions the picture was very
grainy on this channel only, as if the signal strength had
been halved, with some slight flickering: pressing the button
two or three times brought the picture back to normal, apart
from the slight flicker that’s always present.
Check that the vanes of the u.h.f. tuner are not shorting
out at any point on their travel. Check also for poor contact
of the earthing leaves on the tuning gang shaft. For the
patterning, check the earthing screens on the i.f. strip,
especially the plate that screws into the top of one i.f. can.