Sync Separator Diode Replacement

[Jon1967us]

TITLE CORRECTION: HORIZ AFC DIODE REPLACEMENT AND ASSOCIATED PROBLEMS

I’m working on a ‘57 Travler portable b&w which appears to have major syncing issues. The diode shown below was open and needed to be replaced.

https://ibb.co/sKw2zqP
The stock diode was a Selenium, was open and I replaced it with a Silcicon Schottky 1N5408.

I assume this is the sync separator diode? The waveform somewhat looks okish, read at the “-“ end of the diode, but jumps around and looks unstable.

No waveforms are read at both pin 2s of the Noise Canceller (V6) and Sync Sep (V5) and I’m concerned that this may be the wrong diode to use, voltage drop compensation aside.

Waveforms look ok before the Very Osc and after the Vert Outputs.

Is the Schottky ok to use or should I source a different type, even a Selenium? I know my Schottky is installed correctly with the correct polarity at least.