My Paragon II has had an intermittent fault causing no TX power output
in CW or SSB modes. There was always power in FM mode, and in AM mode
carrier but no sideband power. These symptoms led me to suspect problems
in the balanced modulator. FM and AM carriers follow a separate path,
not through the balanced modulator. I opened up the top cover of the rig
today, and did some probing with the oscilloscope. Before I got very far
it started working again. The manual "sort of" explains the operation of
the balanced modulator without being specific about voltages. I have
been monitoring the TD line into the balance modulator, because
according to the manual the balanced modulator is enabled by this "TD"
voltage. The manual does not say what the correct voltage is. I am
getting about 2.7 VDC here when the rig is keyed. This voltage comes
from the CONTROL BOARD, and is switched on by Q7 , which is sourced from
the +REG supply.
I would like to know what the correct voltage during key down is on TD
line. Anyone poked around in this part of a Paragon II?
DE N6KB
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