Kenwood TS-850s Variable CW Monitor Volume
When operating on CW the monitor volume is at a fixed level. This level is set by a preset inside the radio’s bottom cover.
While listening through headphones the difference between the received signal and the CW monitor may become tiring or uncomfortable.
A much better solution would be to enable the front panel monitor volume control in CW mode.
This modification is easily achieved with the removal of one resistor and placing a new resistor in circuit.
Most modifications you will find tell you that you must remove the IF unit. My version of the modification does not require you to remove the IF unit at all.
This modification has been successfully carried out on my Kenwood TS850.
I do not accept any responsibility for damage to yourself or equipment or any guarantees to the suitability or otherwise of any modifications made to your radio. As with any modification, if you don’t feel confident, then please let someone else do it, or don’t do it at all.
Step by step instructions – with pictures
Remove the small surface mount 330K resistor near to VR5. Solder one end of a new 330K resistor at the junction of the SMD resistor and capacitor near IC7. There is a small plate-through hole that may be used as a guide for the end of the new resistor. DO NOT forcefully poke the resistor all the way through, you may damage the through-plating. Bend the leads of the new resistor so that the other end can be soldered to the wiper terminal of VR5. This is achieved by soldering directly onto VR5.
Testing & adjustment
When this modification is completed, either attach an external speaker or the internal speaker.
Power up the radio, select CW, ensure the VOX is turned off and turn the front panel “Moni” control fully clockwise (max volume). It does not matter whether the “Moni” button is “On” or “Off” as the tone will be heard regardless of the button setting.
Using a key, generate CW tones and adjust VR5 for the loudest volume without distortion.
When everything is to your liking, replace the covers and return your radio to normal service.