Sound like a dirty/sticky relay on the RF deck.
Go here and get the service manual: http://www.mods.dk/
73 de Glenn AA5PK

"Asle Fonn" wrote in message
news:1064131565.319657@gurney...
Hi,

I have an old TS-850, it have been with me for over 10 years now.

Lately it have periodic low receiver sensitvity on 40m.
Signals seems to be att. atleast 20 to 40 db.
This happens when switching from tx to rx, sending a "DIT" or two restore
full sensitivity.

It can happend in 7 of 10 tx/rx switching.

Any suggestions?

73,
Asle - LA6IHA