07-01-2016, 11:59 AM
(06-30-2016, 10:06 AM)Steve Davis Wrote: The very first thing to do is, touch the grid cap of the 85 tube with your finger. Do you get a loud hum? Next, place another radio next to the radio under test to see if you can tune the local oscillator of the nonworking radio.
Steve
This is the strategy that should be used with any dead radio - (1) Can you get some hum in the speaker by touching the grid of the last couple stages? Then your audio section is probably working. Otherwise, concentrate on those last one or two stages.
If the audio is working, (2) determine if the LO oscillator is working. If not, concentrate on the LO / converter stage.
If the LO is working, then why is the signal not passing through and reaching the audio stages of the radio? This is where you can get out your signal generator and start tracing a signal through, stage by stage.
Mark K8KZ