Ok, I got 2 TK-790H's that I bought. One turns on and programs just fine, it didn't have ignition sense enabled. It's component board layout is also like what is shown in the service manual. The other one... firstly R504 and R506 were such that it was ignition sense enabled, but I couldn't find R742 and R743 on the component board (pictures to follow). Before I fooled around and looked inside I hooked up power and I could hear a click inside the radio, but the control head did not light up. Then I opened up and removed the jumper resistor and inserted to the correct spot for normal operation (not requiring an ignition wire). The radio still does not turn on, but makes the "click" when 12v is applied to it. The component board layout looks a bit different, didn't know if there was a version 1 or 2 component board? The service manuals "out there" all look like the first photo. Second photo is the one that's a bit different. I know my soldering work is not great but I do have continuity where it counts (also, I unplugged the connector in the left-bottom for the pictures/soldering work only, not left that way)
