Author Topic: Kenwood TS-520- VFO warble  (Read 6285 times)

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Offline KC4UMO

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Kenwood TS-520- VFO warble
« on: February 21, 2012, 07:13:55 AM »
Symptom
VFO warbles, hard to tune in a station. Loose receive when turning the VFO

Cause
VFO capacitor has tarnished at the clip end

Solution
There are two ways to remedy the problem.

First way:
Remove top cover from radio.
Looking down at the VFO unit on the driver tube side you will see a small plate with two machine screws holding it on the VFO cover.  With a right angle screwdriver remove the two screws. This will expose the VFO capacitor. Spray electrical cleaner onto the end of the shaft while turning the VFO. Re-lube the shaft and reassemble. This should work for a while.

Second way:
Remove all knobs from front of radio.
Remove face plate.
Remove VFO bearing with the two screws
Remove the dial
On top of the VFO unit there are 2 screws that hold the LED board in, remove them. Now remove the 4 screws that hold the VFO, 2 on top and 2 on bottom.
Remove the fixed channel board directly behind the VFO, you will also need to remove the support.
Now unplug the VFO and remove it by tilting the rear upwards and pulling it back. 
Remove the rear nut and two top and bottom screws. Remove cover.
Remove the 2 screws that hold the jack in place. Pull the jack out of the slot.
Unsolder the black and red wire.
Loosen the 2 screws on the shaft end. When you fully open the cap you will get to the last screw.
Remove the 4 screws holding the capacitor in.
Remove the stop pin in the rear of the cap.
Put capacitor over a bowl and loosen the nut that holds the rotor in place. Then screw the pivot out.  There is a small ball bearing there so hold the unit over the bowl so it is not lost.

Now hold the cap with the shaft pointing up and press down on the shaft to release the front ball bearings.  You may have to play with them a bit to remove since the grease holding them is over 30 years old.
Fully open the cap and remove the rotor from the stator.
Clean the shorting fork and end of shaft with cleaner and a small brass brush.
Fully clean all parts.
Now reverse the procedure and put all back together
Lube the bearings and gears as you reinstall them.

Unit should be good for another 30 years.