Kenwood TS-950SD Xmit problem

[Edward Cain]

Any Kenwood gurus out there?

   I have a TS-950SD that seems to function perfectly except that it has no TX output on 40M. Receive on all bands and transmit on all other bands seems normal.
   I have the service manual and am perplexed as to how only one band can be dead.

   All advice will be appreciated.

Ed/KJ4JST

[N8ETQ]

  Hey Ed,

     You may have a failed diode or relay or component
on the 40m Band Pass Filter on the Filter unit.  Check
(Feel or listen) for the relays throwing when you go
between 40 and 80M. Don't TX on high power with it since
it may not have a good/any load. Can you hear on 40m?

GL

/Dan

[WZ5Q]

Howdy Ed,
I agree with Dan. The TS-950 series of rigs had a nasty habit of cracking their solder joints on the relay terminals and sometimes the inductors of the TX Bandpass Filters. If you key the rig and see that it is drawing normal TX Current on the Meter with no RF Power Output, then chances are it is a problem in the Filter Unit.
Like Dan said, Be careful with the power level and transmit duration as there will be no load for the finals. There will also be No Automatic TX Power Reduction from high SWR because the Directional Coupler is located AFTER the Bandpass Filters.
Good Luck,

[Edward Cain]

Thanks Dan and Mike for taking the time to respond.

When I key up on 40M I get zero Ic current while other bands seem normal.

Dan, I do get reception on 40M.

Also, from a quick look at the schematic, I thought that the signal path didn't go thru the bandpass filters on transmit.

Please, any other suggestions?

Thanks,
Ed

[Edward Cain]

I need to correct myself.

I do get large amounts of Ic on 40M even with power control fully CCW.

But, does the transmit signal actually pass thru the bandpass filters?

Ed

[N8ETQ]

  Yes it should, The filter unit is between the PA
and as Mike said the internal SWR/ALC stuff.
Sometimes you can get a situation where more
than 1 BPF is selected, IE: one stuck on and it
 can get confusing.

GL Ed,

/Dan

[Edward Cain]

Dan,
   I'm going to try to attach a Xmit flow diagram from my manual. From looking at this, it appears that 40M, 80M and 160M all pass thru a common low pass filter. Thais is why I am puzzled by the fact that only 40M is affected.

[N8ETQ]

  Hey Ed,

    No there are 6 or 7 BPF's in there, My manual has the schematic
on pg 202.  The BPF's usually only cover the Band in question with
a bit of overlap. Almost always less than an octave.

/Dan

[Edward Cain]

Thanks Dan. I have that schematic also, but I thought those filters were only used on receive. Also, If the 40M bandpass filter was bad, would I not have problem with receive also?


Ed

[N8ETQ]

 Hey Ed,

    They are used on both RX and TX. To answer
your question, I go with a resounding Maybe!

   Need to see if the relays K5 and K6 are doing
their thing, and that they didn't break their solder
joints as Mike mentioned.

    I would ensure that the Matrix thing is trying
to select that (and only that BPF) by scoping
L4. Then feel or listen for the relays throwing
between TX and RX.

    Schematic says it covers 4.0 to 7.5 mc.
Tune your rig to 7.5001 and rock it back and
forth while feeling for the relay throw. also would
be interesting to see if it TX's OK on 3.999mc and
7.501MC.

/Dan

You could also switch a relay from another BPF
that you may not use like 160M.

[Edward Cain]

Thanks Dan,
   I will check out K5 and K6. Forgive my ignorance but things are becoming more clear with your help.

Ed

[Edward Cain]

Thank you Dan and Mike.

I finally got around to pulling the filter board and then the relays for 40M. They tested good out of circuit so I put them back in, reinstalled the board and was abput to test voltages from the IC's controlling them. Then I heard the click when selecting 40M and knew all was well.

Reassembled now and working properly.

Thanks again,
Ed/KJ4JST

[N8ETQ]

 Good Job Ed,

      Glad you got him going. Must have been those
solder joints. Thanks for taking the time to complete
the thread.

73

/Dan

[WZ5Q]

Terrific!
Glad you got it going.   

[flintstone mop]

YES!!
It is really nice that someone completes a thread. It helps others who might be doing a Google search, as I have, and all there is, is a lot of back and forth for many pages and the OP never returns replies to any progress. Frustrating.
You did good Ed. Probably a cold solder joint or relay was stuck in one position.
Fred