Electronic Alarms and Home Security Devices - Intercom sound problem

Hope this is the correct area to post this:

I have a Nutone IM-4406 intercom system that works fine except for not receiving any sound (voice, doorbell, radio) at the remote units. You can talk to the master station from the remote units, but cannot talk to the remote units from the master. You can also hear the radio/CD and doorbell at the master station, but not at the remote units. When trying to talk to the remote units from the master, all you hear is a clicking sound indicating the master is trying to talk. While the radio/CD is playing, everyone once in a "blue moon" the remote units will kick in allowing you to hear the radio. But, this is very random and comes and goes.

Anyone have any idea what the problem could be?

Thanks in advance for any assistance.

This is probably as good a location as any.

The installer manual for this system can be found here:
http://www.home-technology-store.com/assets/PDF/NuTone/IM4406ins.pdf

Based on the trouble shooting guide in the manual:

This unit contains a protection device which opens if the audio amplifier detects an overload condition. If the music, chime and intercom audio becomes weak and distorted, remove power from the master station for 10 minutes; this will reset the protective device. If the audio returns to normal, the remote speaker wiring and remote speakers should be checked for bare, shorted and/or mis-connected wires. The problem must be found and corrected before the master station will properly function

There could be mis adjustments in some of the internal settings, but if the system has been functioning normally until now, the symptoms fit.

Thanks. Tried removing all power to the unit for ~15mins but no change.

I looked through the install/troubleshooting manual and didn't see any symptoms that fit. There is absolutely no voice/radio getting to the remote units from the master station. It's not weak or distorted, it's nonexistent. Can't hear a thing except the button clicking. However, the voice from any of the remote units can be heard perfectly clear at the master station (but only at the master, not system wide). This problem has been going on for a long time, just trying to get it fixed for good.

This tells me the problem is at the master station, just not sure what, specifically. What would allow the remote units to be heard at the master, but not allow the master station to be heard at the remote units or the remote units to be heard system-wide?

On a guess, a bad amplifier. The output to the remote units use a different amp than the base unit, on most of this type of thing. It may be a seperate module in the master unit, or it may be part of the motherboard.

Try adjusting the system volume control. It could be that that actual volume control variable resistor is failing.

These things tend to be more proprietary than the alarm systems, I was actually surprised to find a manual online for free...

Thanks. I'll check into it. Also called Nutone Tech sppt line, but the rep didn't know too much and referred me to an authorized dealer/service ctr. I sent them an e-mail, so we'll see how that goes.