ctc12 clone beam current

[Username1]

Hi Timmy, See posting #291, That capacitor C729, take one leg out of the circuit, or remove
it completely and turn the set on and see what the voltage is on the grid of 12BY7A, if
it's still around 20V then the problem is in another part.... Check that first please...

I don't have a Sams for this tv, just the ctc-12 schematic off the internet, so you
have to use the images I put up to see what parts I'm talking about..... And I can
only follow you if you refer back to those part items the same way....
Also you have to understand tube function.... -7V on G1 turns off the tube.
Anything above that begins to turn it on.... +20V It's ON really ON, so it is to
be expected that the plate voltage will be low because the tube is conducting.....
The only other thing I can see checking is R720, a 220 Ohm resistor in the cathode
of 12BY7A. to be sure it's not open....

On resistors in parallel, There is a formula to figure out exact value, but as a
general rule:

30 ohms || 4,000 ohms you will read close to 29 ohms
10 ohms || 20,000 ohms you will read close to 10 ohms.
200 ohms || 200 ohms you will read close to 100 ohms...

Coils, for the most part are going to be low ohms, 30 ohms or less....
a lot of times they are going to be less than 10 ohms....

A lot of times you can check some items in circuit, but it takes time to learn
what you can, and can't and what to expect. Capacitors block DC and pass
an AC signal, they charge and discharge. In the case of this problem, I am
looking for a reason for the grid to be close to 20V, I can see a path to
a 20V source IF that one capacitor is shorted.... So it is wise to check it and
get that possibility out of the way....


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