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Author Topic: Kenwood TS-440S; Dots Gone; VFO Tuning "Jumpy"  (Read 137 times)

WA4ZYN

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Kenwood TS-440S; Dots Gone; VFO Tuning "Jumpy"
« on: November 06, 2022, 06:05:16 AM »

Hello.  I have my Kenwood TS-440S finally "de-dotted".  It required finding replacement PLL and RF boards.  One problem remains: when turning the VFO tuning knob, I notice that the 100Hz and 10Hz digits will lag, jump, or even skip.  It does NOT do this when using the "up" and "down" buttons on the microphone.  It seems logical to me that the encoder itself is at fault.  Before I open up the front of this radio, I would like to verify with someone more knowlegible that this is an actual encoder problem.  I'm reluctant to risk messing up something on the control board PCB's by removing them, unless I really need to.  It seems to me that it is logical that this is an actual encoder issue; can the encoder be cleaned or repaired?

Thank you very much for your time and input.

73,
Francis WA4ZYN
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KD7RDZI2

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Re: Kenwood TS-440S; Dots Gone; VFO Tuning "Jumpy"
« Reply #1 on: November 06, 2022, 08:30:31 AM »

try spraying https://en.wikipedia.org/wiki/Isopropyl_alcohol in the holes of the encoder. it leaves no residue.
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WA4ZYN

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Re: Kenwood TS-440S; Dots Gone; VFO Tuning "Jumpy"
« Reply #2 on: November 10, 2022, 05:24:48 PM »

Thanks for the suggestion.  On the recommendation of a friend, I carefully removed the back of the encoder and found that the slotted disk is not connected to the shaft, and moves a bit, “catches”, then moves a little bit more.  I located a replacement encoder and got it today.  Now I have tuning that is “smooth as silk”. 

I have one issue remaining, and I am hoping someone can tell me if it is a real “issue” or not:  On power-up, the display flashes dots momentarily, then the frequency.  It doesn’t happen again unless I turn the radio off for a while, then power back on.  If I turn it off and then back on immediately, the frequency displays immediately.  I am attaching a link to a video of this occurring:

https://www.youtube.com/watch?v=qqK2mk3n7cc

Has anyone seen this?  I want to get this radio closed up and back on the air.  Any consensus out there?

Thanks and 73,
Francis WA4ZYN
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WA4ZYN

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Re: Kenwood TS-440S; Dots Gone; VFO Tuning "Jumpy"
« Reply #3 on: January 19, 2023, 10:02:22 AM »

Update 1/19/2023:  I see I haven’t posted in a while.  I have made slow progress with this TS-440.  I now have no dots!  Receive works fine.  I replaced the wonky encoder, and now tuning is perfectly smooth again like it should be.  I have no transmit power output, though.  DRIVE level from the RF board measures at about 90mV (and I think it should be around 600mV).  I am going to measure voltages and signal on the PA board to make sure all is well there.  I did lift the leads of the final transistors, and the junctions all check out OK on my Fluke DMM.  There do not appear to be any shorts or opens.  I gave up on the radio for a while, but have renewed interest in defeating this thing’s problems.  I hate giving up.

That’s the latest.  Thank you to any and all who may read my post.

73,
Francis WA4ZYN
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WA4ZYN

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Re: Kenwood TS-440S; Dots Gone; VFO Tuning "Jumpy"
« Reply #4 on: January 26, 2023, 06:49:26 AM »

Please see my more recent thread for the latest. . .  .
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