[R-390] More C709 Info

[Miles Anderson]

Whoa!
I wouldn't be so quick about digging into the PTO chassis. There is almost
no elbow room, and the unit was designed so that the bypass capacitors have
virtually zero lead length. This should be a last resort.
First of all, you should really get a fix on your instruments before jumping
to the conclusion that the PTO output is too low. It probably is low, but I
would try to calibrate your scope before coming to a definite conclusion. If
you have an accurately calibrated VOM or digital meter you can calibrate the
scope at 60Hz using a filament transformer as a source. Unless there is
something radically wrong with the scope, the frequency response at 2-3 MHz
shouldn't be much different than at 60Hz.
If the PTO output is definitely low you can check most or all of the bypass
capacitors for leakage by unplugging the PTO power lead and tube and
measuring the resistance to ground from the screen and the plate. I assume
the plate & screen voltages of the PTO are correct. Check these if you have
not already done so.

Miles Anderson, K2CBY
16 Round Pond Ln
Sag Harbor, NY 11963