Correction, I am not sure in the below posting if I am using the proper
names of the King KX 170B conversions/makers. I believe McCoy and Michel
made conversions of several kinds. MAC may be part of a conversion name
(representing McCoy?). Anyone know the history of these buggers?

Mike

I have a 1967 172 with a MX 170B nav/com. I noticed not long ago that
the display was flickering from bright to dim. Now the radio will not
come on at all. Any suggestions.

The "MX" is a replacement front end to the original KX 170b (made by a
defunct company called "MAC" if I remember right). It contains the
circuitry to convert the original non-lit frequency display "wheels"
into a more modern segmented lcd display. Most of these displays in
other radios contain a photocell to adjust the brightness according to
the changing conditions (from full sunlight to night). I am not sure if
this conversion readout has such a setup, but that may be the problem.
These cells and their related circuitry are usually pretty reliable though.

I have not taken an MX apart to see all that is involved, but it seems
reasonable that there some sort of connector from the MX front end to
the rest of the radio. This connection may be in need of
inspection/reseating. Call around to the avionics shops. One of them may
know a bit about these critters and may be able to save you some
troubleshooting time.

Anyone ever done this conversion?

Good Luck,
Mike