09-08-2008, 08:59 PM
Hi Mike
Sounds like an oscillator coil problem to me.
You mentioned rewinding the oscillator plate winding...is is usually the oscillator cathode winding that goes bad. (This is the outermost winding.) The turns count, size of wire and direction of winding are all critical. Even though the late version 89 sets use a Type 77 instead of a Type 36, it is still that finicky autodyne circuit that is not inherently stable.
Besides rechecking your windings, I strongly suggest you bake your oscillator coil in an oven at 200 degrees F for about 30 minutes to drive out any residual moisture. Afterward, spray the coil with clear lacquer or coat it with clear nail polish. This will help prevent future moisture absorption.
Of course, for a permanent fix, you could perform my Super 89 Mod by changing the 77 to a 6A7, and re-rewinding the oscillator coil to the specs given in the post linked here. It is far more stable than any autodyne circuit. But, of course, it also destroys the originality of the radio. Just a thought.
Sounds like an oscillator coil problem to me.
You mentioned rewinding the oscillator plate winding...is is usually the oscillator cathode winding that goes bad. (This is the outermost winding.) The turns count, size of wire and direction of winding are all critical. Even though the late version 89 sets use a Type 77 instead of a Type 36, it is still that finicky autodyne circuit that is not inherently stable.
Besides rechecking your windings, I strongly suggest you bake your oscillator coil in an oven at 200 degrees F for about 30 minutes to drive out any residual moisture. Afterward, spray the coil with clear lacquer or coat it with clear nail polish. This will help prevent future moisture absorption.
Of course, for a permanent fix, you could perform my Super 89 Mod by changing the 77 to a 6A7, and re-rewinding the oscillator coil to the specs given in the post linked here. It is far more stable than any autodyne circuit. But, of course, it also destroys the originality of the radio. Just a thought.
--
Ron Ramirez
Ferdinand IN
