04-09-2014, 11:25 AM
Rich, I overlooked your voltage measurements. It sounds like the problem is likely in the audio section. I noticed the plate voltage is lower now. Double check any connections around the tube, and preceeding tube. Could have a blob of solder, whisker or something .
I'd also like to know, what do you touch that causes a screech? How are you connecting the generator to your radio for the tests (what kind of leads, etc)
I mentioned removing the cap connector from the 75 tube and injecting a signal on the tube. If something is pulling it (the grid) down, this will remove the loading. I may have missed it, but I didnt see a voltage reading on the grid G1 of the 75 tube (cap connector). Also, if you dont get anything, try removing the 75 tube, then inject a signal on the the 42 grid. I wonder if something is pulling the signal path to ground.
Hopefully this will help you more throughly trace down the location of this problem.
I have noticed oft when the caps in the power supply are replaced the B+ will be higher, esp if higher values are used. Also, I think our a/c line voltage is higher. When there have been previous repairs or attempted repairs, it can really be tough trying to figure out what has been done, or not. Roger, some shots of that section and power supply might help him greatly.
I'd also like to know, what do you touch that causes a screech? How are you connecting the generator to your radio for the tests (what kind of leads, etc)
I mentioned removing the cap connector from the 75 tube and injecting a signal on the tube. If something is pulling it (the grid) down, this will remove the loading. I may have missed it, but I didnt see a voltage reading on the grid G1 of the 75 tube (cap connector). Also, if you dont get anything, try removing the 75 tube, then inject a signal on the the 42 grid. I wonder if something is pulling the signal path to ground.
Hopefully this will help you more throughly trace down the location of this problem.
I have noticed oft when the caps in the power supply are replaced the B+ will be higher, esp if higher values are used. Also, I think our a/c line voltage is higher. When there have been previous repairs or attempted repairs, it can really be tough trying to figure out what has been done, or not. Roger, some shots of that section and power supply might help him greatly.
If I could find the place called "Somewhere", I could find "Anything"
Tim
Jesus cried out and said, "Whoever believes in me , believes not in me but in him who sent me" John 12:44
