The KENWOOD KT-6040 TUNER - Rotary Encoder Problems
The rotary tuning control will fail after prolonged heavy use. The original component is an inexpensive rotary encoder using mechanical contacts, similar to a switch or potentiometer, which will eventually wear, resulting in erratic tuninmg. A drop of contact cleaner will restore operation for a period, but this requires disassembly work for access to the encoder. If you are going to the trouble of disassembling the tuner front panel, it is strongly recommended to fit a couple of capacitors, which will prolong the useable life of the encoder almost indefinitely. Sony have used capacitors here, and tuning problems are not often reported with Sony Tuners.
A truly excellent improvement would be to substitute an optical rotary encoder, as used in typical amateur transceivers, which would never wear or jump, but you would have to find a suitable component, and this would need slight mechanical changes to the encoder board.
DISMANTLING
Access: remove cover (6 screws), then the front cover (5 screws).
Unclip front panel and turn over to give access to the rear of the PCB's. This is sufficient access to add the capacitors.
Solder two cap's, value in the range 10 - 47nF (22nF is about optimum, a film type is recommended) in the positions shown, which is between the two data lines and ground.
To replace the encoder itelf, remove the 3 PCB screws, pull off the knob and release the 11mm nut behind it, and unclip the PCB
Suitable replacement encoders are available from time to time, although the mechanical details vary with the supplier. There are usually a few "rotary encoders" on eBay, and stock no. 265-1723 from RS Components (rswww.com) is suitable if you change the pin connections:
A bit of soldering and drilling will finish the job!
