Have TS-820-S and readout is intermittent. ie 20 meters reads 16 mhz, 15 meters reads 23. mhz, etc. After 15 minutes or so it starts working right...next time I turn it on it does this again but soon reverts back to normal. Any hints? Note: this is the TX-820S not the TX-820. tnx, de Bill, N4DH