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The main trouble with this set is high e.h.t. With the set h.t.
control set correctly, i.e. for 190V at the junction of
R58/R59, the e.h.t. is 27kV. If the h.t. is set to reduce the
e.h.t. to 25kV the voltages throughout the set are low, giving
poor contrast, width etc. With the e.h.t. at 27kV there’s
defocusing on peak whites, while at 25kV there’s smearing
etc. There’s also a loud caption buzz.
This is clearly an early model – the resistors in the h.t.
supply were rearranged in later production. If the e.h.t. is
high with P701 set for the correct h.t. voltage and 40V at
the emitter of the line output transistor, it’s likely that the
flyback tuning capacitor C52 is faulty. It should be replaced
with the correct type from GEC. Replacing C119 (220µF)
which decouples the 12V supply to the TCA270 in the if.
strip should cure the smearing, while fitting an extra 470µF
capacitor across C187 on the sound board should overcome the caption buzz.

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