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Old 11-22-2010, 09:07 AM
DaveWM DaveWM is offline
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Join Date: Feb 2009
Location: Orlando FL
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Back to it, after watching some other programming I seem to have a vert linearity issue, not unlike what CTC17 has been fighting on a RCA with a like circuit.

The only clue I have is the vert drive to the vert output of the 6FG7 is low, 200v PP vs 270vPP. Upping the boost supplied plate voltage (by reducing the resistance thru the dropping resistor from the vert height resistor) increases the grid drive, and give more vert deflection, enough to work with (right not the vert height pot is maxed out, and the lin pot is used to just fill in the screen but results in a egg shaped linearity problem).

the is not wavefore given for the plate of the multivibrator, the grid drive to the multivibrator is correct (160v PP). the grid bias amount was measured with a VTVM and was correct -38v at that point.

From what I have read about multivibrators, the RC network feed back is fairly critical to shape the wavform that starts as a pulse from the vert output. I am starting to wonder if the problem lies there, that is the biasing being done by the linearity pot is not the problem, but is trying to compensate for a defective wave form from the mutivibrator.

Or to put it more directly the height is fine, its the shape of the drive that is the problem, I will take another look at that shape.


in this set the linearity pot is connected to the grid of the vert out.

I am just not checked out enough on the complexites of the RC feedback loop to know exactly where to look, but there are a few precison caps and resistors in that chain that I will start with.
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