|
Couplate substitution
The 6-pin thing was called a "couplate" and it was maybe the first kind of IC ever. Passive, of course.
If you are in doubt about it, better take it off and put discrete components instead. The 5-tube superhet circuit was almost the same, no matter the make or model. See the attached pic.
The couplate not only includes components for coupling the volume control to the 12AV6 grid, and the 12AV6 plate to the 50C5 grid, but also the 150 pF IF filter capacitor between 47k/volume control and common negative. Thatīs why if it is defective you could have good audio but no radio reception.
I changed the phono-radio switch diagram, it had an error in your drwg.
Of course you could have any other cause of no reception in the converter/IF stages, and not on the couplate. Check first whether they are working: change capacitors, tubes, check the variable capacitor for shorts, you may even need to use a īscope to isolate a defect in the IF cans without changing them.
But if the couplate is the guilty one, put in discrete components the good old Cuban way.
|