KUBA PORTA-COLOUR

The trouble with this I lin. transportable colour set, which
also seems to be known as the Granada Colourette, is no
luminance. I’ve tried a new PCL200 luminance output valve
without success. The fault started with it taking about ten
minutes for the luminance to appear. Then after a few days
the luminance packed up completely. Colour is still present
– the set uses colour -difference drive.
Amongst the many unusual features of this set is the fact
that the luminance drive is a.c. coupled to the common c.r.t.
cathodes (the tube is an in -line gun type), with no clamping.
Also the luminance delay line comes after the luminance
output pentode, i.e. between the pentode and the c.r.t.
cathodes. The delay line itself is a possible offender, and can
be checked by simply shorting it out with a piece of wire.
Otherwise, check back from the c.r.t. cathodes, including
the coupling capacitor and the resistors in the luminance
output stage. We’ve known the fault to be due to a defective
output connection on the board.