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Discussion in 'Radio Circuits, Repair & Performance' started by KI6KIS, May 13, 2019.

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  1. KI6KIS

    KI6KIS Ham Member QRZ Page

    I have a TS-450S Kenwood that if you turn it on everything seems normal the meter jumps back and forth but no sound comes out even if I press the voice button nothing no sound out of any place on this radio it use to work. I contacted a guy once he had me check some terminals still nothing . I am at a complete Los in what to do I have the manuals and diagrams that came with it I looked at those till they got blurry. Please does anyone have any ideas suggestions I am at my end I wish I knew more about the workings. Thank You Rod
  2. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    Did you try plugging in headphones?
    K7TRF likes this.
  3. K7TRF

    K7TRF Premium Subscriber QRZ Page

    Yeah, if the rig appears normal, tunes across frequencies, switches bands, maybe transmits into a dummy load but doesn't have audio out I'd start by checking the two places where there are switches in the audio line: the headphone jack and the rear panel external speaker jack. If you get audio out of either of those (start with the headphone jack as Steve suggests) then you probably have a bad switching connector or a bad internal speaker.

    If you can't get audio out of either of those jacks then it's likely a problem in your audio board or some other late stage in the receiver especially if the S meter seems to behave normally with an antenna connected as you tune around the bands. IOW the S meter seems to respond to signals as you tune around and general noise floor otherwise and the S meter readings drop when you kick in the RF attenuator.

    There are a lot of tests you could perform to figure out where your receiver goes dead but they depend in part on what test equipment you have access to. Start with the simple functional tests, do the displays seem to indicate the rig works other than the receiver audio? Does it transmit into a dummy load? Those alone tell you a lot about power supplies, oscillators, IF strips and the like and might let you focus on just the audio issues. If the S meter seems to be responding to signals as you tune around the bands and band noise then it's likely that a lot of your receiver is working fine and things like T/R switching are working. If not, then your issues might be further upstream in the receiver.
  4. G4COE

    G4COE Ham Member QRZ Page

    You could try some a squirt of contact cleaner in the headphone n' external speaker socket and then plugging the plugs in and out a few times.... if the common terminal is oxidised it will prevent it passing the signal on from the audio output chip.

    Another test is to check the signal on the input of the Audio chip, a scope, a little audio amplifier or a Hi-Z magnetic earpiece dabbed on the input will give clues... I built a little LM386 with a small speaker and volume control powered from a 9V battery for such purposes.

    These Eastern wonder magnetic Hi-Z ear pieces work wonders..... one boss thought I was 'loony', prodding and poking about with one of these, my finger on the outer terminal and the other hand on the chassis - not recommended with tubes and their high voltages mind.

    LOL, reminds me of an apprentice engineer.... he adapted a Thorn 1500 black n' white TV chassis for headphones, these things have a live chassis, worked a treat until late one night - until the high wattage dropper resistor melted the drooped wire... "KER BANG", sizzle sizzle sizzle - did his ears no good either.

  5. KA5IPF

    KA5IPF Ham Member QRZ Page

    Check C104 in the IF unit for leakage. The audio goes thru it. Common problem.
  6. AA5CT

    AA5CT Ham Member QRZ Page

    Scope the low-level audio/data jack in the back ... does it show a signal?

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