Friday, January 6, 2012

Colin B. Kennedy Model 20B radio repairs

Recently had some new problems occur with my CBK 20B:

The RF decoupling capacitors on each stage of the TRF circuit were going bad.  At least one or more were shorting out.  I neglected to replace these initially because they were in nice metal enclosures, but after watching some of bandersontv's videos on re-stuffing caps i decided to re-stuff these.

The caps look great, but the radio still did not work properly.  Stay tuned for more...


  1. Hey Greg, I'm at the same point as you on my CBK20B. I replaced the PS electrolytics and powered it up to just hear some crackles. Looks like I'm restuffing the decoupling caps as well.
    On your last comment did you mention that you restuffed the caps and it still didn't work?
    Or are you in the process of restuffing?
    Let me know, I will be eagerly watching your progress. If I find anything significant I will post again.
    Thanks and good luck!

  2. Rob, thank you for your questions.

    I did end up re-stuff the coupling caps. It did not work for two different reasons:

    1. one of the windings on one of the RF transformers was open, so i had to re-wind it.

    2. The RF input transformer had a 75 ohm pot in-circuit before it, acting as an RF attenuator. This pot was inside the control grid rheostat. The wiring for this is factory, not a crappy repair. I removed this pot from the circuit and the radio works excellently now.

    The date codes on my decoupling caps read 1931, so my radio was a later production and my only guess is that by then they must have been goofing up things at the factory....

  3. Greg,
    Thanks for the quick reply.
    Interesting. I hope I'm just facing some shorted caps, not sure if I am up to rewinding a coil yet.
    My CBK20B is the earlier one with the push pull 45's that matches the diagram.
    Going to take me a couple of weeks to restuff the caps, I'll post back when done.

  4. Bob,

    These RF transformers are very easy to re-wind, you can handle it if need be. If you look around my blog from Dec throughout this month you will see a post somewhere where i show this happening.

    You can check each one using an ohm meter to be sure before your re-install your chassis.

    Not many turns, very easy to do. Wire from antique electronics supply, i think i bought a few spools worth of various small sizes.