Jack wrote:

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.

It appears there may be an adjusting pot for the display brightness
control. A twist of this control slightly in either direction may bring
the display back or do nothing at all.

Good luck,
Mike