[Kenwood] TS-940S

[ad6zu at comcast.net]

You might be getting RF into the mike.  The MC-60's are notorious for that.  Try it with the preamp in the mike off and use the mike gain control in the radio.

You can also try it by hooking the mike directly to the rig and bypassing the mike base.

If that solves it, there are circuit fixes for RF getting into the MC-60, but it is easiest to simply leave the preamp off and go directly into the rig.



Roy AD6ZU
 -------------- Original message ----------------------
From: "Troy Warren" <k5oh at mptelco.com>
> 
> 
> 
> 
> 
> 
>  I just acquired a TS-940S/AT that appears to be in very good condition
>  except it has a transmit audio problem. Would appreciate some help on this.
>  This is my first Kenwood HF radio. Maybe someone has had this or similar
>  problem with this rig. Would also like to know if there is someone who 
> works
>  on these radios in case I can't repair it. Here is what I have done so far.
>  The receiver works great.
>  All of these tests were done with the radio connected to a dummy load and
>  the RF control at minimum ( I also tried it at various power levels. I
>  checked the output (key down in CW) with a bird wattmeter and it was 100
>  watts plus on all bands.
>  I hooked up a brand new, out of the box, MC-60 microphone.
>  I pushed in the "MONI" button and keyed the mike. I talked into the mike 
> and
>  increased the mike gain to about 9 o'clock (number 2 on the dial) while
>  watching ALC on the meter. The audio sounded great. I turned on another
>  receiver to monitor the audio and it was very distorted and the ALC meter
>  was very erratic.
>  I removed the top and bottom covers and checked all of the connectors that
>  I could see on the IF, RF, and Control units (boards). All looked okay. I
>  removed all of the plugs (connectors) on each of these boards and coated
>  each pin with a Deoxit pen and plugged them back in to their receptacles. I
>  also lowered the front panel and did the same for all of those connectors. 
> I
>  also checked the battery voltage on the back of the sub display. It was 
> 2.94
>  volts DC. The problem still exists. The receiver still works great and all 
> of the
>  displays are good.
>  I don't think it is the microphone because the audio sounds great with the
>  MONI button pushed however I do not have another mike to try.
>  After looking at the block diagram it appears that the IF unit (board) may
>  be okay since the MONI feature is near the output of the board.
>  Any help would be appreciated.
>  email:  k5oh at mptelco.com
> 
>  Regards, Troy, K5OH
> 
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