[R-390] R-390 (Non A) Problems

[David C. Hallam]

My R-390 has developed a problem.  I wonder if anyone has experienced a
similar condition and what they did to correct it.

The receiver suddenly seemingly lost sensitivity and the carrier level meter
was not responding.  I checked the tubes in the carrier level circuit, both
with my tube tester and by substitution, and found no bad tubes.

Testing the stage gain as outlined in paragraph 53 of the manual, I used my
signal generator to supply a 14.2 MHz signal to test point E206 (grid of
V201 1st RF amplifier.)  A signal of 12 uV gave me a reading of -7 V on the
diode load terminal.  Spec for this test is 4-16 uV to obtain -7 V.  I still
have to do an additional test with input at the antenna input where the spec
is 1-4 uV in case the problem is in the input transformers.  However, as I
read the result of the first test, the receiver is probably working OK.
There is still no movement of the carrier level meter, or at least only a
very slight movement off of zero.

David
KC2JD