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Originally Posted by yagosaga
Values for the first triode of 6CG7:
!!! The reading of the test meter at the grid (pin 2) is -3v instead of -27v. !!! No sync while contacting with the testmeter - it was not possible to adjust correct synchronisation while testing.
!!! Testmeter at kathode of 6CG7 (pin 3) reads +12.6v instead of +5v. !!! Ohmmeter reads 228K between grid and ground, this seems OK.
Between grid (pin 2) and ground 1.27M, has to be 1.3M according to the manual. OK.
R608 with 156K, OK.
c609 has 0.0047 instead of 0.047. The guy, who had done the recapping job before must mistaken it. (Or not?). I replaced c609 with 0.047. Now -18v at grid of 6CB5 and horizontal output current 210ma.
Without c609 I read -22v at grid of 6CB5 and horizontal output current 200ma. What are the correct data for c609?
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Are you using a vtvm or dvm to measure the voltage? A vom will load the circuit at pin 2 since it's input resistance is lower than that of the circuit you are testing. You need to use a vtvm or a digital meter or scope to check the voltage at pin 2 of the 6cg7.
R608 shows 100k not 156k.
My guide shows c609 as .047. However they have been known to be wrong.
It certenly seemed to work better with the .0047.
I do notice in the list of production changes that on some sets they omitted R602 the 1 meg resistor.
I also notice that r603 which shows 82k has been 100k 120k and 150k.
What is the plate voltage on pin 1 of the cg7? It should be 300volts? I would double check the values of the resistors in this circuit especially r 608. Resistors are cheep I might just replace them. I know it is shotgunning, but sometimes it is the only way to find something breaking down at full voltage.
I do not think I would add a drive control since none was there in the original design. On the ctc 7 they added a drive control. They lifted the ground end of r603, changed its value to 100k and connected it to .0033 cap then to 250k pot to ground. There are some other changes to the 6cg7 circuit though and it used a 6dq5 output tube.