Kenwood TS-430 IF board replaced; no CW sidetone or VOX xmsn

Discussion in 'Radio Circuits, Repair & Performance' started by N3MT, Apr 26, 2012.

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  1. N3MT

    N3MT Ham Member QRZ Page

    Hello, I recently replaced my IF board in the TS-430S but now I don't have the CW sidetone. And related to this I'm sure, the transmitter will not key with VOX turned on. If I flip the Send switch and attempt to send CW, I still do not have a sidetone, but the transmitter will transmit correctly. In order to listen to what I'm sending, I would have to turn the volume up on my external keyer.

    Anyone know what may be causing this? Perhaps one or two of the 20-sum odd plugs in the IF board need cleaning? Thank you.
  2. KO6WB

    KO6WB Premium Subscriber QRZ Page

    Perhaps cleaning the connectors would bring the unit back to normal. It's also possible that when you replaced the board one or more of the connectors broke the solder contacts on the pins going to the board.
    Looking at the service manual for the TS-430S I didn't see a connection between the VOX and the side tone. There might be one. The side tone oscillator is a twin tee type. It is on the IF board. The level adjustment is VR10.
    See if any of this helps and tell us how you've done.
  3. W5RKL

    W5RKL Ham Member QRZ Page

    It's quite possible one of the following component(s) is/are bad and/or improperly adjusted on the IF Unit board (see 440's IF Unit schematic on page 79 side tone oscillator board X59.1060.00 on the IF Unit).

    1. Q301 (side tone oscillator) is bad
    2. D301 and/or D302 are bad
    3. Side Tone audio level pot, VR9, is turned down too low

    Ensure plug J10 on the IF Unit board is fully seated on the board.

    Check for the presence of the side tone oscillator signal, with the CW key pressed in CW Mode, at the IF Unit board's J3 pin 3.

    Check the voltages shown on the IF Unit schematic.

    Based on what you said, transmitter produces RF output in CW only when the SEND switch is turned ON but there's no CW side tone, it appears the CW side tone is not working or possibly the side tone output level pot is turned

    You didn't say but why did you change the IF Unit board?

  4. N3MT

    N3MT Ham Member QRZ Page

    Thanks for these suggestions guys, I will check as many of these as possible (to the extent of my competency!) So far I've only tried adjusting VR10, and that hasn't changed the sidetone.

    Not sure if the comments regarding the 440 board will apply to the 430 I have, but I will see if any of the components mentioned are common between the two rigs.

    The reason I replaced the board in the first place is that I accidentally cracked an inch or so of the circuit board itself while removing the AM filter some years ago (yeah, big oops). Several pc traces were damaged, but sidetone and CW VOX still worked - only transmit power and receiver quality went down if I recall.

    Finally, (and I apologize if I overlooked a comment), even if I got the sidetone problem resolved, that probably doesn't mean the VOX will start working again, correct?

    Thank you!
    73, Mike
  5. KO6WB

    KO6WB Premium Subscriber QRZ Page

    Correct Mike, there may be a common link between the two and you will need to trace the schematic to find out what that is. I have looked at the schematic and without reading how the circuits are supposed to work I was just going around in circles. That's one crowded board. The good news is the VOX circuit is an on/off switching type of circuit. Those are easy to troubleshoot with just a DVM. This switching may also be used for the side tone. Just read the description on how the circuit is supposed to work and look for something in that circuit that isn't doing it's job.
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