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Hello neighbor! Look in the manual. There is a diode switched capacitor on the
top of the PTO box that is adjusted to fix that problem. I have successfully replaced a bad diode with
a generic 1N34 from my junk box. I have
no idea how or why that diode would go out but it’s an easy and quick
repair if you find the capacitor isn’t adjusting the USB/LSB offset. Of course it could also be an aged crystal. Ian, K6SDE From:
collins-bounce@xxxxxxxxxxxxxxxxxxxxx
[mailto:collins-bounce@xxxxxxxxxxxxxxxxxxxxx] On
Behalf Of K6XN Team, my understanding is that crystals Y15 and Y16 provide
the proper BFO frequency relationships to the mechanical filter passband in a
75S-3 to yield optimum audio response from the 75S-3 product detector. I also
understand that crystal Y15 is the crystal used for LSB and crystal Y16 is the
crystal used for USB. When I zero beat my 75S-3 against the calibrator signal
the receiver zero beats at the same dial frequency position for AM, USB and CW
EMISSION switch positions provided the BFO control set to zero. If I leave
everything else alone and simply switch the EMISSION switch to LSB I have to
move the tuning dial up in frequency approximately 2 ½ KHz to zero beat. Is it
time for me to replace the LSB crystal Y15? I suspect this problem will also
affect transceiver operation in LSB mode with a 32S-1 or 32S-3 transmitter
using the 75S-3 receiver to control both receive and transmit frequencies. I
would very much appreciate learning if others have experienced this and what
they did to remedy it. Thanks, Ted, K6XN |