The 10 most common problems with a NuTone IM /IMA3003 Music Intercom System

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, built-in AM/FM radio and a digital clock.

The models manufactured 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 change 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 was a Factory Modification to convert early models if needed.

The 3003 does have 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 surround 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 throughout 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 Remotely mounted Ceiling Speakers:

    IS76:  A round Ceiling Speaker with a 8" speaker cone, used with IC/ICA301 remote control

    IS75:  A round ceiling speaker designed 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. 

Update on Thursday, September 13, 2012 at 9:52AM by Cindy & Christopher

POWER SUPPLY PROBLEMS:

The #1 problem with 3003 systems has 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, and 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 failure state, you will notice that the radio, door chime and intercom functions will not work, although the clock will still show the time.  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.

THE SOLUTION:

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.

THE OUTCOME:

After rebuilding 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 other side of the heat sink.

Here are all of the old capacitors.   

ASK A QUESTION

Update on Friday, September 14, 2012 at 7:40AM by Cindy & Christopher

CHIME MODULE PROBLEMS:

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 fed 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. 

A Guaranteed Way to Ruin a IM3003 Master Station

Contrary to what many people think, better is not always good.  This IM3003 was modified by a previous owner in an attempt to improve the quality of the sound from the master station.

The original NuTone speaker cone was replaced with a somewhat larger size speaker cone from Radio Shack.  There are many problems with this idea, but the biggest problem is that NuTone uses speakers in the IM3003 which are rated at 25 ohms.  The Radio Shack speaker cone was rated at 8 ohms.

The little amplifier IC in the IM3003 cannot supply enough current to drive a 8 ohm speaker.  The 8 ohm speaker will overload the amplifier, causing it to run burning hot and quickly fail.  This is exactly what happen to this IM3003.  Upon initial testing the amplifier heat sink became smoking hot after the set was powered on for about 1 minute..

A normal repair for a IM3003 of this age is to rebuild the power supply and clean the controls. This IM3003 also required having the amplifier IC and voltage regulator replaced.

The overall sound quality of any Intercom system has more to do with the design of the amplifier than it does the speakers it drives.  Buying the highest quality Bose speakers and connecting them to your NuTone intercom system will not make it sound like a Bose system, it will just ruin your intercom system

Is the Display on your IM3003 Faulty?

I had a NuTone IM3003 come into the shop this week with a very unusual problem.  The display on the IM3003 Master Station would not show the correct FM Radio frequency readout, it just displayed 198.9 regardless of how the tuner wheel was rotated.  The tuner worked correctly; it was just the readout that was faulty.

One thing to understand about the tuner/display on a IM3003 is that the tuner is not a digital tuner, like on a modern radio.  The tuner on a IM3003 is an analog tuner (mechanical) that has a digital readout connect to it.  

While it is not that uncommon to have the readout on a IM3003 display be out of alignment or have the clock run fast or slow, I cannot remember ever the last time I saw a unit with a failed display.

The problem was traced down to  IC201 on the display PC.  IC201 is a Sanyo LC7250 CMOS, Digital Frequency Indicator w/Clock LED Function IC.  This is an interesting chip which actually has more features than are used in the IM3003.

Unfortunately this chip is at its "end of life" cycle with chip manufacturers and the availability is limited and somewhat expensive.  The cost is around $18.00 for a single chip.

Removing this 42 IC requires some careful desoldering. A proper desoldering tool should be used.  Installing the new chip is straight forward, being careful to not have any solder bridges between the pins.

With the new chip installed, the display worked correctly again; however, it was necessary to realign the trimmers on the board so the readout matched the radio station that was being played.  I also adjusted the clock to the proper frequency so it will keep the time correctly. These types of adjustments require specialized bench equipment that many Service Centers may not have.

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Water Damaged IM3003

Water damage is one of the worst things that can happen to your IM3003 Master Station.  Usually this happens when the home has a leak of some type, either from your roof or a plumbing problem.

It also happens a lot of the time when you have wallpaper removed and the room repainted.  Removing wallpaper is done with water-based solutions and while washing down the wall, the water gets inside the IM3003.

Because of how the circuit boards are mounted on the back of the IM3003 faceplate, the display board and the amplifier board sit horizontality (like shelves) on the back of the faceplate.  The water will puddle up on these boards, causing all sorts of damage.

Electronic circuit boards that have been damaged by water will have a green corrosion around the electronic components on the circuit board.  If the corrosion is left for a long period of time (weeks) it can ruin the circuit board.

Master Stations with water damage will exhibit very different types of problems than master stations that just have the typical, common failures.  This is because the green corrosion is conductive (it can make small electrical connections) which create short circuits on the board, between different components.   These short circuits will cause random problems and can also damage or ruin components.

When a water-damaged Master Station is delivered to us for repair, it is almost never a typical repair.  There is additional work to clean the boards and additional time to troubleshoot components that are water damaged.  These units are almost always more expensive to repair.

This display board is from a IM3003 that has water damage from wallpaper removal.  The shiny coating on the board is from the wallpaper removal solution.  The red arrows point to the corrosion caused by the water.  In this case, the board will require a new display IC chip ( the large chip in the center of the board) because the corrosion has shorted out the chip.  The replacement components cost $24.00

This area of the power supply / amplifier board controls the intercom functions.  The red arrows point to more of the green corrosion.  

Another view of the same board.  This board will be cleaned in an ultra sonic cleaner to remove the corrosion before it is repaired.

More corrosion around the amplifier IC and voltage regulator.

Water stains on the amplifier insulator card are a good indication of what happened to this IM3003.

NuTone IM3003 Water Damage - Part 2

Sometimes water-damaged Intercoms will require extra effort to repair the damage caused by the circuit board corrosion.  This NuTone IM3003 was originally damaged 2-3 years ago and nothing was done about the problem.

The corrosion was so bad that it had eaten away the metal leads on many of the components.

The red arrows point to the leads of 2 diodes that were completely eaten away and were no longer connected to the circuit board.

The corrosion has also eaten away the leads from several capacitors on the board.

Here are the capacitors after they were removed from the board.  The leads are almost completely eaten away by the corrosion.

The only correct method to rebuild such a severally damaged board is to remove all of the components and clean the board.

Inside the red boxes you can see that all new diodes have been installed in place of the damaged parts.

The red arrows point to the new resistors that have been installed.  The blue arrow points to 4 ceramic capacitors that were also replaced.

New electrolytic capacitors are installed on the board.  These would have been replaced as part of the normal rebuild process of a IM3003 power supply board.

Finally, the amplifier IC and voltage regulator (mounted on the heat sink) are reinstalled.  The amplifier IC had to be replaced because its leads were eaten away just like the other components.  This is unfortunate because the amplifier IC is an expensive part.

After this initial repair work was completed, the IM3003 was reassembled and tested.  I found a few other problems with the Intercom Control section on this board.  These were not direct corrosion problems, but they may have been caused by some of the other failures on the board.

After all of the problems were solved, the entire IM3003 was rebuilt and it is now back in service.

If your IM3003 is in need of Repair, use this link to contact us

Use this link link to our Intercom Reapir Request Form.