09-27-2015, 01:34 PM
Hi all! Back again!
This time, I've got a 48-475. Replaced all the caps (left most of the mica), checked wiring, replaced resistors if out of tolerance. Got a hum that varies with volume, but not too concerned with that as it will probably go away once I figure out this problem.
I inject an audio signal on pin 3 of the 7C6 ("D" of section 2) and get a good, loud output from the speaker. But when I inject the same signal on pin 6 of the output tube ("B" of section 2), I get no audio. All it does is silence the hum. Tube checks out O.K., but someone did replace it (should be a 7B5) with a 7C5.
Looks like the 7C5 should work in place of the 7B5.
Voltages everywhere check out O.K., albeit about 20V low.
I've spent waaaaaaaay too much time on this radio already, since it had extensive repair in the past. But I did trace down all the wiring, and everything looks O.K. The only componet that was NOT in the radio was R312 (6.8Meg), but that goes to WS-2® which should only affect FM.
This is only half the schematic. I'll upload the other half if needed.
[Image: http://i1367.photobucket.com/albums/r796...ccckac.jpg]
Ideas anyone?
Thanks,
Pat
This time, I've got a 48-475. Replaced all the caps (left most of the mica), checked wiring, replaced resistors if out of tolerance. Got a hum that varies with volume, but not too concerned with that as it will probably go away once I figure out this problem.
I inject an audio signal on pin 3 of the 7C6 ("D" of section 2) and get a good, loud output from the speaker. But when I inject the same signal on pin 6 of the output tube ("B" of section 2), I get no audio. All it does is silence the hum. Tube checks out O.K., but someone did replace it (should be a 7B5) with a 7C5.
Looks like the 7C5 should work in place of the 7B5.
Voltages everywhere check out O.K., albeit about 20V low.
I've spent waaaaaaaay too much time on this radio already, since it had extensive repair in the past. But I did trace down all the wiring, and everything looks O.K. The only componet that was NOT in the radio was R312 (6.8Meg), but that goes to WS-2® which should only affect FM.
This is only half the schematic. I'll upload the other half if needed.
[Image: http://i1367.photobucket.com/albums/r796...ccckac.jpg]
Ideas anyone?
Thanks,
Pat
