[R-390] My R-390

[Flowertime01 at wmconnect.com]

George KA5DEN,

When R390's smoke on the bottom side you go looking for some 47 ohm 2 watt 
resistors.

There are four in the power supply under the 26Z5's and four more in the 
audio deck under the 6082 regulator tubes. There intent is to balance the 
current through the two haves of each tube.

They cascade in failure. Likely once upon a time a 1/2 of a tube went to 
failure. The 1/2 bad tube smoked one 47 ohm resistor just as little bit not 
enough to discolor the marking. So the tube was changed and the receiver 
returned to service.

Now the other 1/2 the tube gets more current and always fails first. 
Eventually the 47 ohm resistors go up in smoke as the tube is run to the end of 
its useful life.

If you need to change one, then change them both. Mostly you do all four in 
the module.

Time to run all the tubes through a tube tester. Pull the power supply deck 
and Audio deck and do an eye ball.

Resistors go quietly.
Caps pop.
Selenium stacks leave you with signal from the antenna when you go to 
calibrate.

Find a PDF copy of TM 11-5820-357-35 for your R390. Think of it as a bad 
movie and memorize it.


Roger AI4NI