I'm trying to fix my R-4A, looking for help diagnose and repair. Unfortunately I don't own a signal tracer or an oscilloscope.
When initially powered on, the R-4A works normally for about 5 minutes. Then, static will build over period of about one minute, with no received signal, followed by a “pop”, and normal reception will resume. After about a minute the sequence will happen again. After being on for about 30 minutes the receiver will behave normally. I had been dealing with the issue by just turning on the receiver awhile before wanted to use it. Yesterday, after being on for about an hour, listening to a station on 40M LSB, reception stopped, and static started, building over long period of about 3 minutes, followed by a “pop” then normal reception. So, evidently the problem is getting worse. Today I am going to open it up and try changing out some tubes. Guessing to start from the RF amplifier because since static is always present am guessing the audio stages are fine. Could a problem in the AGC circuits cause this behavior? Thanks in advance, Curt KB5JO
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