[Kenwood] R-5000 in trouble

[Dr. Gerald N. Johnson, electrical engineer]

If its loops unlocked it may be frequency dependent with different loops
for different frequencies. Or one thing that shows up in Kenwood service
bulletins for radios with that symptom is a poor connection in the PROM
socket in the controller board. The official factory cure is to rip out
the socket and solder the PROM to the board. Do it one pin at a time and
you will be more successful. Pry off the plastic part of the socket
leaving the individual pins to heat and pull one at a time.

If it is socket, probably lifting and reseating the PROM will cure it
for a while. A 1/10 drop of DeOxit from Caig on each pin with that
little mechanical cleaning should be a more permanent cure easier to do
than soldering the PROM to the board (as if Kenwood would ever do an
update on the PROM). Use the dropper bottle, don't spray the stuff, you
don't want it to soak up the board and insulators in the area. You want
it just on the metal to metal contacts.

If its PLL unlocking it may be that R-5000 has the same problem as many
TS-440 with a potting goo that is hygroscopic that when damp loads down
the oscillator (FET) until it won't oscillate. The Japanese synthetic
bee's wax is hygroscopic. The cure is to remove all the wax, especially
that under the oscillator and control transistors. Usually needs a few
new parts from their destruction on removal, I hear. Then use a less
hygroscopic anti microphonic stuff or none at all. I did clean up a KDK
with the same problem once by heating the wax to liquid with a hot air
gun. That seemed to drive out the water and it worked for me for a
couple years after that and for others as far as I know. It sure was
easier to boil off the water than to remove the stuff.

73, Jerry, K0CQ

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Entire content copyright Dr. Gerald N. Johnson, electrical engineer.
Reproduction by permission only.