Quote:
Originally Posted by old_coot88
OK. That's close enough for now. At least you've verified B+ on C3b.
The identical voltage should be appearing on pin 6 (screen grid) of the 5AQ5, and on the bottom of the output xfmr primary (red lead).
In other words, there should be solid continuity (zero ohms) twixt all those points. (Forget the negative voltage issue for now) Main thing is to find out what connection's gone open.
With the set OFF, and an ohmmeter set to RX1, connect the black lead to pin 6. With the other lead, check for zero ohms to bottom of xfmr primary (red lead), and to C3b. You'll probably find the connection to C3b is what's open.
BTW, also check the xfmr primary for a few hundred ohms between pins 6 and 5 (plate) of the 5AQ5.
Once this is all sorted out, check for solid continuity (zero ohms) from C3's can to ground. Any resistance here could be contributing to the 'negative voltage' condition.
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OK, I think I may have figured it out, and I should have figured it out sooner, because I had this issue before with the old GE tombstone radio I was working on previously, but I think maybe the negative lead of C3B isn't actually making contact with the chassis (its soldered in place but its not actually contacting the chassis its just "floating" there.
I'll check for sure when I get a chance, right now I'm trying to help my parents clean up water in the basement of their new house because the irrigation system backflow burst on them last night because it froze (because they forgot to turn the water off to the irrigation system before it started getting cold, because this was the first time they've had an in-ground irrigation system in a house so they didn't know you had to shut the water off to it.)
I may be slow on the uptake but I do eventually figure it out.
