[Studio263]

This fault is normally caused by a duff colour decoder IC, random flashovers in the tube can damage it. I've got loads of panels for these, PM me if you would like a set for the signals side (that should get it going).

While you are there, make sure that a link has been added between the emitter of the line output transistor and ground. Originally this went through the scan coil plug to disable the line output stage if the coils were unplugged, however it only takes a slight increase in resistance at any of the various contact points to ruin the transistor so its best to disable the arrangement (as B&O recommended at the time). The electrolytic capacitors in the base drive circuit of the line output transistor should also be replaced if they look a bit care-worn, use Matsushita 'FC' series ones (from RS Components etc) as a durable replacement. That's another B&O tip from the period, these sets developed a reputation for random line transistor failures when they were only a couple of years old but these measures fix that.

Also note that the wiring is a bit flimsy and apt to break where it goes into the various plugs that link the PCBs together (most especially the white stuff). Wires can snap off anywhere so it is worth giving anything in the suspect area a little tug to make sure that the cores haven't broken under the insulation, many hours of my time have been wasted tracing the results of this little problem.