Zenith Console combo

[old_coot88]

Originally Posted by DaveWM

replaced the 4 diodes, put all back together, started the setup, some smoke, pull the board. The pot that was getting hot was the left blue horz. someone had jumpered a 47 ohm 2 watt resistor. I noticed it but decided to leave it be and try as is after the diode swap. Removed the wire jumper (was very sloppy), and replaced with a 50ohm WW resistor (all I had on hand). the resistor that was in there that had been jumped over just fell apart so my guess is it was high or open and the jumper was just being cheap, prob ok as long as the pot was not turned to far.

Convergence is MUCH better now, only issue I have is one of the right side coil forms is stripped (the slug just pushes thru.

I may pull the board again and see if I can find a inner threaded section to fit into the existing bore. Or I could just glue a non metalic extention to the ferrit slug, and wrap it with some wax paper or some other friction fit. Or just try and get it set and then tack glue a drop of white glue (just enough to hold it, so if it needs to be reset it would break free.

could use some idea from other that have had to deal with this...

First off, those coil forms that Zenith used tend to crystalize from heat and fall apart after a few years. If yours haven't fallen apart, the set is probably very low time. Also, concerning one of those blue coils (forget which one, been a lotta years), if you run the slug too far out (or if the slug is missing), it will fry one of the wirewound pots. This is probably what's happened in your case.

For that stripped slug, you could take a very thin strip of rubber from a bike inner tube (but not a gum rubberband which will rot) and lay it full length inside the form, then push the slug in. The strip will provide a friction fit and you can still adjust the slug as needed.

You might consider a small muffin fan to keep the conv. board cool, to slow deterioration of those coil forms. BTW, RCA conv. boards will also smoke a pot if one of the blue slugs is turned too far out. A little tidbit worth bookmarking. Bill(oc)