[TenTec] Ten Tec Omni D Intermittent Receive Problem

[piper cub]

Just recently, I began to have a problem only on the recieve portion of the radio.
Sometimes I am receiving an S9 SSB signal level, then it goes down to an S-zero signal level. I can still hear  the other party talking but at very low signal level, S-Zero. 
Then it will suddenly come back to normal typically in about 10-15 minutes.
It does not seem to affect transmit at all. It occurs randomly, sometimes when the radio has been on for several hours, but even stranger when I actually turn it on, it does the same thing. But only occasionally does it do it?  Sometimes it will work fine for 8 or so hours, sometimes only 15 minutes.
I have the matching power supply but have also tried different power supplies with exactly the same problem happening. Have read previous posts regarding the T/R reed switch being faulty, but I am not sure that is the problem.  
To me a relay is either on or off, no in-between, so I do not think this is the problem, then again I may be wrong.
Anyone out their can give me some ideas or solutions.
Appreciate any help I can get.
Barry Fitzsimmons
KA8ENC