The sound and picture are normally excellent, and this
situation can last for three or four days. Sometimes
however there is good sound and vision for about four
minutes after switching on, then the sound becomes distorted and noisy, the colour goes, and finally the
monochrome picture breaks up. Retuning restores a good
colour picture and sound for a few minutes, then the fault
returns. This happens on all channels. The set also occasionally jumps from channel 3 to channel 1.
The first problem is that the tuner is drifting down the
band slightly. If this trouble is due to the tuner, it could well
be that the tuning voltage supply feedthrough capacitor
C37 is leaky. If the problems lie in the 29301 electronic
programme selector module however (we’ve often found
this to be the case) it’s best to return it for exchange/repair
as sophisticated test equipment is require to deal with it.