Batboard

I have one of our FD's Minitor IIs that won't activate the alert tone upon receiving the proper QC tone (when in silent mode). In monitor mode, the receive works just fine. I tried a different reed and it's the same. What's the first thing to look for in these?
Also, where is the test point to inject the audio tone (and mv level) so I don't have to keep trying to activate it with an RF signal?

Try looking at the ribbon flex were the active filter socket is. Were the ribbon cable is soldered to the board, it usually cracks and no longer makes connection right at the board. If you use a little pressure forma tuning tool, you can check the 2 outer traces. One of these is almost certainly broken. That's the obvious at least. (Given that it worked before and the tones haven't been changed.)

Good luck
PH