GRUNDIG 5011GB

About a quarter of an hour after switching on there is a
pronounced whistle, lasting for perhaps half an hour. A
vertical bar, slightly
brighter than the overall picture
brightness and approximately half an inch wide, frequently
appears to the left of centre on the screen.
There is a clip on the top of the input/commutating
transformer 9245-834.21 in the line output stage. Check
that this is secure and that the cores of the other wound
components in the line output stage are neither cracked nor
loose. Check Tr506 (BF259) which drives the width
stabilising transductor,
and the associated diodes,
particularly Di504 (1N4004) which is in series with the
transductor.