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Symptom:
After transmitting for approximately 2 hours at 50% duty with 150 watts output the temperature protection circuit activates reducing the output power to about 50 watts. Normally, full output power will be restored after the fans have had a chance to cool things down. Occasionally the power output will not return to normal, even after extended receive operations.

Cause:
The temperature sensor is attached to the main transformer and is set to activate at 80°C. This setting was selected to reduce power before the internal fuse on the transformer opens.

Correct action:
After through testing, we have found that the temperature sensor should be set to 90°C to allow proper return to full power transmit. This setting will also allow the radio to be used at higher ambient room temperatures without worrying about the power output dropping in the middle of a QSO.

Parts required:

Qty Description Kenwood Part No. Circuit description
1 90°C Thermal switch S59-1416-05 S1
I cant seem to find this part anywhere. Not even Kenwood has it. Please if you can point me in the proper direction i will forever appreciate it.....

Hi Doug
Try ken@k3ten.com or N4ATS St Cloud Fl.Both are GREAT TECHs.Bill N4ATS fixed my TS-690S disolay problem that Kenwood West coast service couldn't find,bad solder joints on caps.
73 & good luck
Paul KB3LMV N.Fl

Thanks Doug, I will keep the info you passed me. If worse come to worse might just have to go that route...

This symptom only happens on AM. No other modes are Affected