This may not be relevant to the problem some of you are having. However, I have a Maverick ET-733. I have a problem with the plug in receptacle on the transmitter. The plug in keeps popping out of the receptacle. When this happens I get a reading of HHH on both the transmitter and receiver. The first time it happened I thought it was a faulty probe. So, I changed the probe and the same thing happened.
It took me some time, but eventually and accidently, I discovered that I needed to insert the probe into the meat, then put the transmitter in a spot where nothing could cause the wire to move and then plug in the probe to the transmitter. Even a slight breeze would cause the probe plug in to pop out of the receptacle.
I sent Maverick an email suggesting it was a problem with the receptacle on the Maverick transmitter and that the transmitter should be replaced. I thought this was reasonable since the ET-733 was brand new and under warranty, but they thought otherwise. So, I now use a big wide rubber band to help keep the probe plug in in place.