12-30-2011, 10:47 PM
Hey Tom
That sounds a bit like problem I've been having with that confounded 600. It's fairly intermittent but the volume will drop to about half and will get very noisy. The only thing that brings it out of this operation is to touch the plate pin of the 6A7 with a screwdriver. It will go pop and work fine for a week of so then back to it's old tricks.
It's a bit hard to troubleshoot because it seems that the mixer and IF/det don't behave well separately. The mixer needs the loading of the IF can and the regenerative det needs load from the secondary of the IF can.
I've double everything I can think of, pulled the IF transformer checked the windings, resolder all the connections, cleaned the ground connections and then ran ground wires to be sure, tried several 77's and 6A7's
I'm starting to think the tube socket may have some sort of high resistance path.
That's my stumper.
It's funny all of the other 4 toobers(80's,81's,84's,37-84's) I've worked on haven't been too much of a problem. Mostly the same old bad coils, caps,and resistors. Did have one with a bad IF transformer but was able to repair it.
Terry
That sounds a bit like problem I've been having with that confounded 600. It's fairly intermittent but the volume will drop to about half and will get very noisy. The only thing that brings it out of this operation is to touch the plate pin of the 6A7 with a screwdriver. It will go pop and work fine for a week of so then back to it's old tricks.
It's a bit hard to troubleshoot because it seems that the mixer and IF/det don't behave well separately. The mixer needs the loading of the IF can and the regenerative det needs load from the secondary of the IF can.
I've double everything I can think of, pulled the IF transformer checked the windings, resolder all the connections, cleaned the ground connections and then ran ground wires to be sure, tried several 77's and 6A7's
I'm starting to think the tube socket may have some sort of high resistance path.
That's my stumper.
It's funny all of the other 4 toobers(80's,81's,84's,37-84's) I've worked on haven't been too much of a problem. Mostly the same old bad coils, caps,and resistors. Did have one with a bad IF transformer but was able to repair it.
Terry
When my pals were reading comic books
I was down in the basement in my dad's
workshop. Perusing his Sam's Photofoacts
Vol 1-50 admiring the old set and trying to
figure out what all those squiggly meant.
Circa 1966
Now I think I've got!
Terry
![[-]](https://philcoradio.com/phorum/images/bootbb/collapse.png "[-]")
