[boxdoctor]

During my short, (and not very enjoyable) time at Comet (Sandiacre), I repaired quite a few of these sets. As has been said, the triplers were always a good candidate for failure.
Comet service issued a mod. sheet which gave simple instructions for increasing the video gain on the driver assembly on the tube base PCB of some models. It appears these sets were supplied not fully modified to PAL I standard, and required extra gain to fully drive the tube cathodes on PAL I signals. Tony.