Wellllllllll...........egg on fact time.  To make a 1625 light up inside like a light bulb, first get fancy and build an add on 'This might be cool to do' thing,  putting a 300MA meter in one of those old Bud slope front metal meter metal boxes you just found in you chassis junk box collection,  put in a toggle switch that swaps the meter from the plate to screen circuit, wire it into your harness between the MD7 and the transmitter rack, and make the mistake of swapping the plate and screen leads in your fancy meter box.   That'll light up your 1625 cheerily.

Charlie, W4MEC in NC