I am in search of a replacement GEMAC MV/I transmitter, and 70TC Programmer. Would also be interested to know if anyone knows of a direct replacement device. This was the pre-Mark V/VI or anything, and pre-Speedtronic temperature control system.

 

GE sold the GEMAC instrument line to Bailey Controls (now ABB) back in the early 1970's. I don't know if ABB still supports this line.
MV/I transmitters (also known as temperature transmitters) are available from other sources - Google temperature transmitter. However, what you have is likely a 10-50 ma system rather than 4-20 ma, so you might have some trouble there. I would be pretty certain that the thermocouples are iron - constantan (Type J) so you would need to specify that as well. Power source may also be an issue - I don't remember whether the original was loop powered or needed a separate power supply. The temperature transmitters I have used recently have been loop powered.

Hope this helps - good luck.