Re: {Collins} 75A-4 Problem - RX on 160 Meters Only



Chuck -

The Crystal Oscillator, V4, isn't!! :-) Possibly a bad Mixer (V3) but less likely. Get your DeoxIT on the crystal switch wafer.

73, Garey - K4OAH
Glen Allen, VA

Drake 2-B, 2-C/2-NT, 4-A, 4-B, C-Line
and TR-4/C Service Supplement CDs
<www.k4oah.com>

Hallett Jr, Chuck W wrote:
I recently acquired an operational 75A-4 which tested Okay on all bands.  After about two hours operating time, all  bands except 160 meters are essentially dead, but 160 works like gangbusters.  Reading the manual tells me the receiver is dual conversion on all bands except 160 meters.  This provides me a clue as to where to start looking.  Rather than reinvent the wheel however, I ask for the groups wisdom.  If this is a known issue, I would appreciate your advice.

What I have done is remove the bottom plate and used DeOxit on the band switch with no noticeable results.  One odd item is a very strong signal heard on 160 can be faintly heard when the band switch is rotated to 80 meters without moving the tuning dial.  I note the frequency on 180 is the second harmonic of the 160 meter frequency.

All of the components appear to be original.

Thank you & 73 de Chuck K4SC






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