[Penthode]

With the initial RF-IF-baseband channel alignment done (including setting traps. Last week while checking the I channel I traced a self oscillation to an open 20uF chasis mount capacitor. I had on hand an NOS triple 20uF 450v which I replaced. (The rest of the original chassis mount electrolytics are original after reforming and checking for leakage. I must have missed the one that was totally open).

All testing so far has been minus CRT. Time now to next test the chassis connected to the 15GP22. Using a set top box, I had scoped good video up to the CRT grids. The sweep circuits were good and there was good high voltage available to feed the convergence, focus and second anode connections.

I managed to get a stable picture with lots of brightness and good contrast. I noticed the Keyed AGC is a bit wonky and need to investigate this. After this setting up colour demodulation, purity and convergence.

The 15GP22 seems to have very good emission. The tube is a rebuild: are the bright filaments normal?