PHilco Predicta 9L37 assistance

[noah300g]

I've restored a number of Predictas, but currently my oscilloscope is broken, so I can only measure voltages and resistances on my current resto project, and I've hit a bit of a snag. Hoping for some experienced assistance.
The set has good sound, so I know RF/IF Audio are all ok. Screen has good brightness, full vertical and horizontal deflection, but no video. All paper and bumble bee caps have been changed, along with a few resistors that were out of tolerance. All resistance measurements are now close based on Sam's photofact values. Since there is no video, I can't tell if I have proper sync recovery or just a video problem. Two voltage readings that I find suspicious are on the 6AW8 tube. Pin 9 shows 190V on schematic, fed from 280V source, but I measure the full 280V on that pin. Pin 8 shows a direct connection to the 140V source, but I am only getting 120V there. Resistance measurements show correct, though. I also have good brightness. Might I have a problem with one of those couplets K2/3/4/5, or is it something more fundamental than those causing the incorrect voltages on 6AM8?
Any help appreciated.

[maxhifi]

280V on the plate of the 6AW8 tells me that the tube is not conducting. Check for an open cathode resistor, open screen resistor, bad ground, or intermittent socket. Predicta sockets have reliability issues, where pins lose connection to the board. My guess is you need to replace the 6AW8 socket.

[noah300g]

Thanks,
The socket is a little wonky, in that I had to wiggle the tube to get filament conductivity to make the TV work at all (series filament set). I seem to have correct resistance readings from pins when tube is removed, but I'll double check.

[maxhifi]

Originally Posted by noah300g

Thanks,
The socket is a little wonky, in that I had to wiggle the tube to get filament conductivity to make the TV work at all (series filament set). I seem to have correct resistance readings from pins when tube is removed, but I'll double check.

Still, the only way to get zero voltage drop across the plate resistor is zero current. This could be caused by an open connection in the cathode, or screen grid circuit, or even between the plate pin and the socket, or it could be caused by low or inadequate screen voltage. it could also (less likely) just be a bad tube. You found the issue here, just need to resolve it now.

[maxhifi]

So based on this image, first check continuity from pin 6 to ground. You should get about 68 ohms. Then check continuity from pin 7 to ground, you should get 680k. As for pin 8 being low, this is a slight concern, but 20V low would not cause the 6AW8 to not conduct at all.