Kenwood 120s problem . Need help

Discussion in 'Radio Circuits, Repair & Performance' started by OG6Z, Feb 15, 2021.

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  1. OG6Z

    OG6Z Ham Member QRZ Page

    om's i got an old ts 120 to my hands , now i desperately need your help.
    The problem is that there's No tx and No rx what so ever .
    It turns to all bands after i cleaned the car oscillator unit and knobs ett.
    I've checked the Q1 transistor back of the the oscillator .it seems to be Ok.
    So now im stuck. Any ideas where the problem of No rx and No tx might be ? And what causes it ? Is It worth to try repair it or is it just a piece of junk?
  2. WG7X

    WG7X Platinum Subscriber Platinum Subscriber QRZ Page

    Just a thought: What position is the FIX/VFO switch in? If it is pushed in (FIX) position and no crystal installed it would do as you say: no RX/TX. I did that once myself.
  3. W1NB

    W1NB XML Subscriber QRZ Page


    In my opinion, any radio that is in reasonably good physical and cosmetic condition is worth an attempt at repair but I also realize that not everyone likes the challenge.

    There are a couple of key areas that come to mind; oscillators and voltage busses. If you haven't yet, I recommend downloading the service manual. It can be found here:

    Below is the block diagram for oscillators and conversions. Note the sections common to both transmit and receive are the carrier oscillator, the VFO, the counter unit and nearly every mixer and buffer stage. I don't know what you have to test equipment so its hard to recommend a method of process other than to say you will need to check each stage. If you have an oscilloscope, use it to check the inputs and outputs to each of the oscillators, mixers and buffers. There is additional documentation in the manual to help guide you. Just use your scope probe on the 10x setting so you don't load the circuits down. Voltage readings are noted on the schematics in the manual. If you have only a voltmeter, or when you are trying to pinpoint an actual component failure, you can use the voltages to determine failed components.

    If you have specific questions as you walk through the process, post them here. There are several very capable technicians who will respond, especially if the question is specific.

    TS-120 Block.jpg
  4. KD0RCB

    KD0RCB Ham Member QRZ Page

    Im wondering how you "cleaned" the car bd...Did you spray it with a lubricant, air-blow, etc? Any oil based lubricant, sprayed into small, adjustable trimmer caps, (or on touchy areas), would be detuned to the point that they would either be dead, or way off freq. The caps would probubly have to be replaced for a successful repair..either way, as suggested before, is to check with test eqpt, which osc's are running , and if on frequency or not. Just follow the schematic, good luck.

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