B & 0 3400 CHASSIS

There’s a colour fault on this set. Complete loss of colour
may last for a full evening, then return the following day –
usually about five minutes after switching on.
There are many possible causes of no colour on this
chassis, but by far the most common one is failure of one of
the high -voltage transistors in the decoder. You may find
BF110 or BF178 types fitted – the latter should be used for
replacements. The transistors to check are 4TR13 and
4TR6/7/8. The faulty transistor will be betrayed by the
following voltage readings: collector at the 60V supply line
voltage, emitter voltage zero, base voltage high.