Kenwood TS120s Display problem-Suggestions How to fix the problem

[colincolin30]

Hi,
I have owned the rig for 20 years and had no problems. Recently I have noticed the blue frequency display does not display numbers just two dots appear when i first turn the rig on.
I also note there is no audio level even if the audio knob is fully advanced.

I left the rig on for about 30 minutes and noticed the frequency would display on 14mhz only and the audio level is now audible. Tuning around I can hear stations in QSO's.
Connecting a dummy load i can transmit 100watts into the dummy load. Obviously a component when it warms up starts working and the rig comes back to life.

Now for the million dollar question!

Where would I start to investigate this problem?

The VFO module or the display module.

Has any one had the same problem?

Has anyone suggestions. I at first thought it was the rotary switches so I cleaned all wafers with a spray can of switch cleaner material.But that was not the solution.
Recently I downloaded the TS120S circuit diagram but the size of the components is very small to even try and fault find the circuit.

Any help , suggestions or ideas how to fix my problem would be greatly appreciated.

cheers for now
Colin

73 VK2JCC Sydney, Australia

[w5rkl]

I haven't seen a response to your question. Did you get the 120 fixed yet?

The problem is most likely caused by loss of the CAR Unit signal to the PLL Unit. The PLL Unit will turn the display OFF and basically shut the transmitter and receive down by disabling the VCO oscillator if any of the required signals are missing.

I recommend you clean the CAR Unit and PLL Unit board plus and ensure they are fully seated to each board. Check each boards mounting screws, loosen each screw 1 full turn then tighten.

73s
Mike
W5RKL