[ICOM] no ptt transmit on IC-761

[Fern]

I just acquired an Icom IC-761 today. At times, the radio will not transmit with ptt (it's definitely not the microphone as I've tried 3 different mics) but at times  it will work using the  VOX option. Also, the manual xmit key will not key up the transmitter. I have done the cpu reset with no improvement. It lost the frequency display at one point and then came up with 77E shown in lieu of the frequency. Shutting the radio off and then back on will restore the frequency display but still no manual ptt for xmit. Has anyone seen this problem? Any help with this would be greatly appreciated.  73 from Fern