Kenwood ts-930 no am xmit.

Discussion in 'Radio Circuits, Repair & Performance' started by KM4YTW, Jul 9, 2020.

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  1. KM4YTW

    KM4YTW Ham Member QRZ Page

    I just noticed last weekend that AM mode didn't work. I receive fine but when I hit the key in AM mode nothing no relay action , nothing. Stays in receive mode. Any idea where would be a likely culprit ? S1 and S2 mode switch ?
    Thanks
     
  2. N8YX

    N8YX Ham Member QRZ Page

    Which serial number '930?

    There were two runs, and the earlier ones implemented a different power-control scheme than the later units.
     
  3. KM4YTW

    KM4YTW Ham Member QRZ Page

    It's a 600 series serial number rig . Everything works in all modes except AM transmit. Put, send button work fine . AM reception is great too.
     
  4. N8YX

    N8YX Ham Member QRZ Page

    Look at the Carrier control and switching circuits related to AM TX. The rig puts out power on FSK and CW, right?
     
  5. KM4YTW

    KM4YTW Ham Member QRZ Page

    I have no TC voltage in AM mode anywhere. Trying to figure out where this voltage originates from. Yes FSK, CW work fine. I checked all the sections on the mode switch and it checked good.
     
  6. KM4YTW

    KM4YTW Ham Member QRZ Page

    Correction not TC but it's TV voltage
     
  7. G3YRO

    G3YRO Ham Member QRZ Page

    Personally I wouldn't bother . . . the TS-930S produces HORRIBLE AM anyway !

    It's Double Sideband with re-inserted Carrier . . . so if your audio peaks just a little too high it becomes unintelligable.

    When I want to operate AM I use my FT101E, which produces wonderful AM (sounds as good as a proper high-level modulation AM rig)

    If I really wanted to use my '930 on AM I would modulate a later stage in the rig properly, like the '101 does.

    Roger G3YRO
     
    K8PG likes this.
  8. KM4YTW

    KM4YTW Ham Member QRZ Page

    Amen to the 101 I have all models except f model . I'm a huge fan of the 101 series ! It just anoys me a lot that something doesn't work. I'll get it eventually. I'll find usually by accident lol.
     
  9. N8YX

    N8YX Ham Member QRZ Page

    There's a mod for the TS-940S which modulates the RF pre-driver by way of replacing its emitter resistor with an appropriately-spec'd audio transformer. A bit of work but according to those who have done it the results are worth the trouble.
     
  10. KM4YTW

    KM4YTW Ham Member QRZ Page

    I've got it narrowed down to no TR voltage . This voltage is derived from IC11 on the signal board. It comes from a network mess of AND gates and NOT gates. The signal from IC11 pin 10 is the TR voltage which biases Q92. That's not happening.
     

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