[Ron Ramirez]

I measured +24.8V where the schematic calls for +23V.

So I put a 1K and a 68 ohm resistor in series; the 1K measured slightly high and the 68 ohm slightly low; the combination was nearly exactly the 1130 ohms that Ohm's Law called for.

I tried it again. (This was before I saw your post, Mondial.) If anything, the LED seemed dimmer, barely lighting on a stereo signal but going out when tuned off signal.

I then read your post, Mondial, and measured the voltage going into the MPX board at point 4C. Sure enough, it is +24.3V.

Oh, and I tried your suggestion of grounding point 4C but it sparked when I placed the free end of an alligator clipped lead (the other end was already clipped to the chassis) so I immediately withdrew the lead. I think the LED went to full brilliance but I stopped right there as I did not want to do any harm to the MPX board.

I await your comments before proceeding.