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Best forum for Kenwood TL-922 and 922A ?

Discussion in 'Amateur Radio Amplifiers' started by KM5L, Jan 26, 2021.

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  1. NE2I

    NE2I Premium Subscriber QRZ Page

    Im starting to see bandswitches on ebay for the 922. Are they any good?
     
  2. W1QJ

    W1QJ Ham Member QRZ Page

    The new ones made by Switchcraft I thing it is sells for $180, a bit pricey but it is a superior switch. BUT, I’ve seen one of them burned up too. So it’s NOT a substitute for stupidity.
     
    NE2I likes this.
  3. NE2I

    NE2I Premium Subscriber QRZ Page

    what usually kills those bandswitches?
     
  4. W1QJ

    W1QJ Ham Member QRZ Page

    9 times out of 10 it’s operator error. All the ones I’ve seen were due to that.
     
  5. W1NJC

    W1NJC Ham Member QRZ Page

    I added fuses to BOTH primaries of the filament transformer to hopefully protect in the event of a G-F short. Why both? Because I determined that a fair amount of current can be sourced with only one of them connected. I figured this out when I was testing adding some series R to the primary in order to drop the filament V a bit (mine was at 5.32VDC). I have not monitored the temp of the transformers yet but I did monitor the socket bases/underneath because I heard people saying there was inadequate cooling down there. Even on AM I didn't see temps above 120°F. Maybe I'll check the big iron next.

    I've attached a redline schematic of the mods I've done to my 922...feedback welcome!
     

    Attached Files:

  6. W1QJ

    W1QJ Ham Member QRZ Page

    The simple bias mod is even more effective and should be done anyway even if you put in fuses.
     
  7. W4JFA

    W4JFA Ham Member QRZ Page

    Lou, I did not realize a diode is needed on the grid meter. What diode number do u recommend?
    Bob
     
  8. W1QJ

    W1QJ Ham Member QRZ Page

    The TL922 needs meter protection. A 1n5408 from B- to ground, and back to back diodes across the plate meter which can easily be accessed at the meter board pins up top.
     
  9. W1NJC

    W1NJC Ham Member QRZ Page

    Can you describe or provide a drawing for the "simple bias mod"? I see it mentioned all around but have yet to find a schematic or any details. Also, when you say "back to back" diodes, you mean in parallel facing opposite directions, right?
     
  10. W1QJ

    W1QJ Ham Member QRZ Page

    In parallel in opposite direction yes. The bias mod is simple. It’s outlined at W8JI webpage in his discussion on the subject and I believe he has a photograph.
     

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