The IM / IMA3003 Music Intercom System was in production from 1984 through 1994. During this time there were many electronic updates to the fundamental design of the 3003.
The 3003 is a 3-wire, home run wired system which has room-to-room intercom functions, entry door communication and built-in AM/FM radio and a digital clock.
The models manufacture in 1984-1985 use different amplifier/control and selector control boards than the later versions. With the increased popularity of built-in Chime Modules a changed was made to allow the homeowner to take better advantage of this new option.
To be able to hear the Chime Module throughout an early 3003, it was necessary to leave the power switch in the ON position. If if the power switch was in the OFF position you would not hear the chime tones. A change was made in 1986 which allowed the chime to be heard regardless of the power switch position. There is a Factory Modification to convert early models if needed.
The 3003 does has a true digital clock, however it has an analog (mechanical) tuner. The tuner is connected to the digital display for convenience, but it is not a digital tuner.
There are Room Control Switches behind the door which surrounds the clock. Behind this door are the Intercom Volume and Tone Controls along with buttons to set the clock.
The 3003 uses 25 ohm speakers through the system.
Inside remote speakers are Models:
IS/ISA305 Small inside stations with 5" speaker cones, Ivory, White, Faux Wood Grain
IS/ISA308 Large inside stations with 8" speaker cones, Ivory, White, Faux Wood Grain
Inside wall mounted Remote-Controls:
IC/ICA301 A small wall station with volume and intercom control, no built-in speaker
Inside Remotly mounted Ceiling Speakers:
IS76 A round Ceiling Speaker with a 8" speaker cone, used with IC/ICA301 remote control
IS75 A round ceiling speaker designe to look like a recessed light fixture with a 5" speaker cone.
Inside Volume Controls:
IC901 A wall mounted Volume Control used when creating a Music-Only location.
The #1 problem with 3003 systems have to do with failed power supply components on the Power Supply/Amplifier/Intercom Control circuit board.
When the 3003 was new, if you listened carefully to any speaker you would hear a light background hiss, this is white noise. White noise is the background noise an amplifier makes when it is turned on.
As the 3003 ages the hiss becomes a hum, as time passes the hum becomes louder and then turns into a buzz. These changes in the sound are due to the gradual failure of the components in the Power Supply.
As the 3003 reaches the complete failue state, you will notice that the radio, door chime and intercom functions will not work, althought the clock will still show the tme. If you turn the radio power on and switch the input selector to FM, you will notice that the numbers on the display will continuously change, as if the display were counting.
If left in this condition, the 3003 can have a dramatic failure which will cause greater damage to the amplifier.
Rebuilding the Power Supply in a 3003 is a fairly simple task for a NuTone Service Center. It consists of replacing 10 capacitors and 4 diodes.
More repair will be required for sets that have been left powered up after they have failed.
After rebuild the power supply the 3003 will be restored to its original condition, with only a slight hiss of white noise at each station. This type of repair will extend the life of the of the 3003 for another 10-15 years.
Inside the red box are the power supply capacitors, all of the blue arrows point to the newly installed parts. There are 3 additional capacitors located on the otherside of the heatsink.
Here are all of the old capacitors.
The 2nd most common problem with a 3003 has to do with installations that include a chime module.
Chime modules are Models are:
IA28 which is a 1-2-8 note chime module.
IA29 which is a musical chime module.
When a chime module is installed in a 3003, the interconnect cable is plugged into the Switch Control Board. This 4-pin connector supplies power to the chime module and makes the audio output connection from the chime module to the 3003.
Chime modules have a high gain output (high signal level) and that signal is feed into the switch board through a pair of transistors. Some times when a chime module fails, it will feed DC voltage into the switch board input and cause the transistors to fail.
Chime module failures are not uncommon field service requests. Even thought the chime module has failed the service person will find that a new module will not solve the problem. The switch board failure must also be corrected.