We just installed a new 86" LG with a 3.5mm TRS service/control port connected to an Extron MLC64 serial controller. The control works for all functions except for the most important one: Power On

Extron thinks that the 1/8" TRS port is somehow being powered down like the USB based control, but this doesn't make sense since it should behave like a serial 3 pin serial port. LG has been useless -surprise.

Any Ideas? We have worked with other recent LG's with the same port and had no problems.

Help?