Rick -
Check the DC voltage on the shielded wire at T14 (center pin on side
closest to CAR BAL pot). In CW mode, this voltage should be 0.0 with
the GAIN at MIN, rising to about a volt as the GAIN is turned up. IF
the voltage does NOT go to 0 at MIN, there is a problem with R105/R15,
Rick,
Is this on any particular band? Does the power out vary with position of the
TUNE and LOAD controls? Does this happen into a dummy load? If the PA goes into
parasitic oscillation power out will go full bore with the slightest
advancement of the GAIN control.
Also if there is an issue
Hi Rick,
Sounds to me like your finals are ...taking off somehow, i.e.
oscillating...
What does the monitored signal sound like...? Is it exactly as displayed on
the frequency dial...? Is it raspy-sounding / unstable...?
Those are all sure-fire indicators that you have an instability issue with
Rick -
Check R105 and R106 and associated wiring for continuity and value. If
R105 opens at the bottom (ground) end, R106 or its wiring open up,
full drive regardless of GAIN control setting.
73, Garey - K4OAH
Glen Allen, VA
Drake 2-B, 4-B, C-Line TR-4/C Service Supplement CDs
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