The closest replacement for the VARI-L mixer used in the TR7 is the
Mini-Circuits SRA-3MH+. The SRA-1 is a 7dbm LO mixer and the LO in
the TR7 is right at 13dbm.
http://www.minicircuits.com/products/fm_pic_level_13.html
Also check the 2 pin diodes, CR1401, CR1402, MPN3404 at the front of
the high pass filter. I repaired a TR7 that the owner had connected
the output of another transmitter
to the antenna connector on the TR7 and shot about 50 watts into it.
It seemed to work ok on the lower bands but on 15 and 10 the power
was very low, it was these 2 diodes.
73, Joe KC9LAD
In a moment of carelessness, I inadvertently transmitted into the RX
input of my recently acquired TR-7 while testing the transmitter
output last week.
OK - I can hear the laughter now, and it is well deserved!
So far I have determined:
The rig had zero (or near zero) RF output when purchased - I will
move this problem to the bottom of the list.
The diodes in the CM-1 mixer module on the upconverter board are
shorted - hopefully this the limit of the damage caused by my negligence.
I cut open the CM-1 module with a Dremel, and the diode ring is a
discrete part, encapuslated in what appears to be a ferrite bead, so
the module will have to be replaced.
I have ordered a MiniCircuits SRA-1 mixer from RF Parts, which I
hope will be a direct replacement for the CM-1.
I will post the results of my efforts to repair this rig to the list.
Any comments, questions and or razzing is now being accepted ....
Thanks,
Charles
K5QED
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