Kenwood TL-922A NO Grid Current

Discussion in 'Amateur Radio Amplifiers' started by KA5ROW, Jan 18, 2011.

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  1. KA5ROW

    KA5ROW Ham Member QRZ Page

    Kenwood TL-922A Grid Current

    I just rebuilt my Kenwood amplifiers power supply. Every things works I have high voltage, Filaments work fine, relays key when transmitter closes the relays. Just no grid current.

    This is what I did.

    Replaced all Caps.
    Replaced all bleeder resistors with 10 watt 50 k ohm from 7 watt 47 k ohm. also replaced all the .01 ceramic disk. The only difference I went with 1000 volt instead of the factory 500 volt value of disk stade the same .01.

    Replaced every component on the rectifier board. went from 800 piv to 1000 volt piv at 2.5 amps
    Replaced / changed the 500 volt .01 ceramic disk with 1000 volt .01 and new 1/2 watt equalizing resistors at the same value.

    Replaced a 33uf 160 volt cap at the filament transformer.
    Replaced a 100 uf 16 volt cap at the zener diode.
    Replaced "4" .01 500 volt ceramic disk on the bottom of the 3-500z tubes. The Grids

    any suggestions. I will open it back up in the morning and re look at all on the ceramic disk.
  2. W8JI

    W8JI Ham Member QRZ Page

    Not much of that is meaningful except the filaments light and the relay still closes.

    Does the amplifier show plate current? Does it show any plate current increase or output when keyed.

    My general rule is to not fix things that are not broken because it causes more problems then it cures. None of the parts you changed could cause the problem you have, so something else happened accidentally. :)

    Maybe you opened a wire up or have a bad solder joint around the 16 volt capacitor when you worked in that area, since an open path through the zener can cause what you describe.

    I would have just grounded all the grid pins (three on each socket) with short leads and not used the grid capacitors, resistors, or chokes if it was my amp. I hope you did not follow the bad advice on that website you listed last week.

    73 Tom
  3. KA5ROW

    KA5ROW Ham Member QRZ Page

    Every things works fine now. :D I went back thru every thing step by step looking of a error that I may have made, I did re solder a place or two and fired it up. Works just like new.

    I think what happened, I started this project just before Thanksgiving worked on it for a hour then a week later a little more. Mail order parts then two weeks later work some more, skip a week again.
    If I had ordered all the parts at one time, and in one day did the project every thing would have gone by without a hitch.
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