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1st turn the brightness all the way down, and check the 220k resistor that goes to the brightness grid on the CRT to make sure it is not open.
Predictas are known for bad tube sockets, if the vert tube is lighting up, then try it while wiggling the tube around.
Check the primary of the vert out transformer.
check the pin resistance of the 6DR7 tube to the sams values
425 to the 275v
2.1 meg to ground
2.1 meg to ground
.1 to ground
0 to ground
3.5 meg to the 275v will vary depend on control setting
68k to ground
50k to ground will vary depne on control setting
450 to ground will vary depending on setting
1000 to ground
Check voltages at the tube pins, this is where a socket extender comes in handy.
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