Common Problems with the NuTone IM / IMA3303
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The IM3303 was introduced in 1994 as a replacement for the IM3003. The IM3303 featured many improvements including a more powerful 15-watt amplifier which gave the IM3303 much better fidelity and some actual bass response.
There were separate bass and treble controls along with a Loudness switch, which added 8dB of bass to the music. The IM3303 had a true digital tuner which was displayed in a backlit LCD panel and the tuner had a 12-station radio memory feature (6AM and 6FM).
The two features which drastically improved the IM3303 over previous models were the new "stand-by" feature and the "Remote Radio Control" function.
One of the most common complaints with any NuToneIntercom System was the constant backgroundhiss that could be heard on all of the stations in a home. This hiss was the amplifier's "white noise" and it was something that you just had to live with if you had a NuTone Intercom System.
This problem was solved with the IM3303 by designing it with a "stand-by" mode. When the intercom functions were being used, and with the radio turned off, the IM3303 would be in "stand-by" mode, which means the amplifier was turned off. This allowed the system to be silent on all of the stations.
The stand-by mode also meant that with the system in this third state (stand-by) there could be a new control function added to the system, while still using NuTone IW3, 3-wire cable.
The new feature was "Remote Radio Control", which allowed anyone in the home to turn the radio on throughout the house and scroll through the 12 pre-set radio stations from any of the inside or patio remote stations. The remote radio control functions were accessed with the "End Call" pushbutton on the remote stations. Since the remote radio control feature was designed into the master station and not the remote stations, it would work even if you have stations from the previous IM3003 model. This was hugely popular feature, especially with more and more 2-story homes being built.
The IM3303 used the same design platform as the IM3003, which meant it was backwards compatible with all of the wiring and remote station from the IM3003 system. This allowed customers to have just their IM3003 master station replaced with the IM3303 and save some money.
PRODUCTION HISTORY:
While officially there are only IM and IMA 3303's, there are four different versions of this model. If all four versions were placed side-by-side you would not be able to tell them apart, but they are all very different from each other electronically.
The original IM3303 was manufactured from 1994 through about 1996. These first versions are easy to identify by the interconnect cables on the back of the master station. These early versions use interconnect cables which are made up with individual small white wires, which are terminated into their plug connectors. While I don't have a picture of this version, they are easy to identify by the messy look of the cables on the back of the master station.
The first revision was in 1996 which remained in production until 2001. This second version still carried the IM label and most of the changes were to streamline the manufacturing of the IM3303 along with the newly introduced IM4406.
The IMA3303 was introduced in late 2001 and it was basically an electronic update to the design which was brought about when NuTone changed the vendor who was manufacturing their intercom equipment.
At this point, all of the manufacturing had been done in Japan by two different vendors, but this was about to change. Around 2004, NuTone decided to move the manufacturing to China. While these final units have the same IMA label they are different from the previous IMA versions.
What all of this means is that basically there are four unique versions of the 3303, and for the most part none of the boards are interchangeable.
Since exact documentation on production dates and design and boards changes were not kept by NuTone, it's very difficult to understand which boards are interchangeable with each other. It is best to have your 3303 master station repaired and keep its original boards whenever possible.
COMMON PROBLEMS:
Problem #1. Self-Activating "Remote Radio Control":
Like any new NuTone intercom model there were some initial problems, however they weren't anything to serious with the IM3303.
The most common service call on the original IM3303 had to do with the remote radio control feature.
When this feature is activated, the LCD panel on the master station will display the letters "IU" which stands for "In-Use". When the system is In-Use, all of the other functions are blocked until the In-Use is complete. The idea was to prevent a situation where a user might think that the system had stopped working for some reason.
The problem with the remote radio control was cause mainly by Patio Stations that would have moisture buildup on the switch circuit boards. This moisture would cause small short-circuits and the remote radio feature would self-activate and turn the radio on all by itself...usually in the middle of the night!
What the homeowner would typically see is the LCD display showing a constant "IU" and the radio would switch ON, then the tuner would scroll through the preset stations, then the radio would switch OFF and the cycle would repeat over and over.
NuTone solved this problem by have a sealant applied to the Patio station switch circuit board, which covered the solder traces and sealed the board from moisture.
Problem #1.5
There is another cause for self-activation on the IM /IMA3303. This can be caused by a failure with the 74 Series Logic IC's that are mounted on the Control Board.
These IC's work in conjunction with the micro-controller (read about the micro-control below), and if they are faulty, they can be the source of self-activation problems.
These logic IC's are commonly available and fairly easy to replace with the proper tools.
Problem #2. Improper Intercom Communication:
Another problem with the original IM3303 was erratic Intercom Communications.
This problem was not caused by the typical problems with remote stations or control switch problems, it was with the intercom control relays in the IM3303 Master Station.
Mounted on the Main Circuit Board in the IM3303 there are four micro-relays that control the intercom communication functions. On some units these relays would fail or become stuck and the intercom functions would not operated correctly.
This seems to be a problem only with the IM3303 units that were manufactured in the first 2-3 years and it was not a problem afterwards.
These relays are commonly available and are straight forward to replace.
Problem #3. Discoloration of the IM3303 Faceplate:
Originally the IM3303 was going to be available in 3 finishes: White, Black and Light Maple.
In reality, only the White model was ever produced. Due to an insufficient amount of UV inhibitor in the plastic of the IM3303 Faceplate, the faceplates will slowly turn yellow over time. This is especially a problem with units that get a lot of direct exposure to the sun. Apparently the yellowing is caused by Bromides being released from the plastic by the UV light.
COMMON PROBLEMS with NuTone IM / IMA3303's TODAY:
The original IM3303 is almost 20 years old, and even though this has been a fairly trouble free design, we are starting to see patterns of failures for common problems.
As with all NuTone Intercoms designed since 1984, the IM3303 and IMA3303 are powered up all of the time. Even if you don't use your system very often, it is still accumulating hours day after day. A 20 year old IM3303 will have accumulated 175,200 hours since it was originally installed.
(NuTone IM3303 Power Supply)
As with any electronic device, it's completely normal for the components in the power supply to fail once it has exceeded its normal life expectancy. Fortunately the IM3303 has a simple power supply design and rebuilding it is not a complicated task.
However, there are two other problems which we are beginning to see with both the IM3303 and IMA3303 which are not as easy to solve, and one of them is related to the failure of the power supply.
Problem #4 - Micro-Controller Problems:
All of the functions in an IM / IMA3303 are controlled by a Micro-Controller, which is something like the micro-processor that runs your computer or cell phone, only it has much less processing power.
As an example of what the Micro-Controller does: When you want to listen to the radio on your IMA3303 you push the FM button and the radio turns on. How did this happen? The Micro-Controller did it.
Inside the Micro-Controller is a simple "program",or set of instructions. When you push the FM button you are causing the micro-controller to launch a series of instructions which include many steps, such as:
1. Turn on the red LED indicator next to the FM button
2. Change the LCD display from the clock time to the radio frequency display
3. Display the last FM radio frequency that was played on the master station.
4. Turn the radio tuner on
5. Switch the tuner to the FM radio band
6. Tune the FM tuner to the last FM frequency that was played
7. Turn the systems amplifier on
All of these steps happen almost instantaneously and you would think that they all happened as one big event (like flipping a light switch on), but they are actually a series of events controlled by the instructions in the micro-controller.
This is why the IM3303 and IMA3303 have a reset button. Sometimes after you experience a power outage or a power brown-out, your 3303 will not work correctly. You may not have any radio, or the intercom will not work, or the door chime will not ring, why? Because when the power came back on, the micro-controller came back on also, but it's sort of confused.
The instructions inside the micro-controller are scrambled because of the power outage. This is where the Reset button comes in. When you push the reset button, you clear the micro-controller and restore the instructions from the factory default settings.
This is why when you perform a reset you lose all of the programmed information in your IM / IMA3303, including the time and your favorite radio station presets.
So, how does a power supply failure affect the micro-controller?
We have seen some cases where the customer's power supply had failed (causing a fairly loud hum throughout the intercom system) and instead of haveingthe master station repaired, they simply turned all of the volume controls down so they couldn't hear the hum.
While this tactic eliminated the annoyance of the hum, it did not fix the failed power supply. In each case, more than a year passed before the homeowner contacted us to have their IM3303 repaired.
We expected these to be a normal IM3303 power supply rebuild; however, after the rebuild was complete there were some unexpected surprises.
In one case, after the power supply rebuild was complete that IM3303 came back to life, but, when we were performing the final checkout procedure, we noticed some strange operational problems.
This IM3303 acted weirdly. When the FM button was pushed the red LED lit up for AM, the FM radio turned on, but the display didn't switch to the FM frequency for almost 5 seconds, and the frequency that was displayed wasn't the radio station that was being listened to, until that switched about 3 seconds later. Unfortunately, using the rest button didn't help at all.
When something like this happens with a master right after a repair has been done, it's natural to think that something was over looked or the repair was done incorrectly. The set was pulled apart and we started looking for the cause of the strange operation. Here's what we found:
The Control Circuit Board is where the micro-controller is located. It's a small device about 1" square. We inspected the micro-controller and it looked OK, so the circuit board was removed and when we flipped it over we found a dark brown square on the back of the circuit board, directly under were the micro-controller sits.
The dark brown area indicates that the micro-controller had been very hot for a very long period of time, enough time to discolor the fiberglass circuit board material. The excessive heat in the micro-controller was cause by excessive electrical voltage from the failed power supply.
The erratic operations were cause by the damaged micro-controller which no longer was able to follow its set of programmed instructions.
Now for the really bad part: the micro-controller is not a replaceable component. While the actual component is available to purchase, and while it would be possible to remove the original micro-controller and solder a replacement to the board (with some very specialized equipment), it is not possible to program the new micro-controller because no one has the program, not even NuTone.
The original micro-controllers were programmed when the boards were manufactured in either Japan or China, and when the production ended, the ability to program the micro-controllers vanished.
The moral of this story is that if you have a failed IM / IMA3303, make sure that you get it fixed before the problem causes damage that is almost impossible to solve.
There was a happy ending in the final chapter in the repair of this customer's IM3303, because we were able to substitute a used control board from another IM3303 and get her system working again.
Problem #5 - AMPLIFIER FAILURES:
The IM / IMA3303 has a 15 watt amplifier which is 10 times the output of the IM3003. The amplifier in the 3303 is a robust design and it is more than capable to drive the maximum number of 13 remote stations.
Even thought this amplifier is well designed, we have seen some patterns that indicate the possibility of a dramatic failure cause by either gross maladjustment of the system controls or by shorted wiring between the master station and the remote stations.
There doesn't seem to be any warning with this type of failure. As reported by homeowners, all a sudden the system simply failed. However, there are probably warning signs which were overlooked or ignored by the homeowners.
What we see on these master stations is a drastic failure of the components in the amplifier of the unit.
A visual inspection will reveal two severely burnt resistors (R422 & R426) along with the signs of excessive heat in the area around transistors Q408 & Q406. Typically capacitor CXX will be ruptured also.
While these obvious failures may seem bad enough, there are usually many more failed components on the board.
The typical IM3303 with this type of failure will have 10 shorted transistors, one failed voltage regulator, four burnt resistors, seven failed capacitors and one dead op-amp chip.
A serious by-product of this failure is caused by the heat that these failing components generate. The area of the circuit around these hot components damages the copper traces, and when the failed parts are removed, the traces will lift off the boards and sometimes break.
It is often necessary to solder small jumper wires to bypass the broken traces. In other cases the traces will have to be repaired, which is a very labor intensive process.
The good news is that all of the needed components are commonly available and none of them are very expensive.
See All of the IM / IMA3303 Pictures Here
Ask a question about your IM/IMA3303
Cindy & Christopher
Amplifier Failure:
I had another IMA3303 delivered to the shop with the beginning stages of exactly the same problem I outlined in this repair. Since the IMA3303 had not completely failed, I was able to do some testing before I started the repair.
When the IMA3303 was connected to the two NuTone 301T transformers (16 volts 30VA) the transformers were so overloaded that the output voltage was reduced to under 9 volts on each transformer. The power supply circuits in the IMA3303 are designed to create two separate voltage rails within the IMA3303.
By measuring the current on each transformer it was easy to see which circuit had the fault. By isolating different parts of the power supply circuit (by removing components) it became clear that the output transistor had failed.
Once Q410 was removed and checked I found that it had a short between B (base) and C (collector). I replaced Q410 and reinstalled all of the componets I removed for troubleshooting purposes.
After the replacement of Q410 this IMA3303 worked correctly again. The real question is what cause Q410 to fail? I suspect that the problem is with the installation wiring for this system.
If there is a short on the Center-Red wiring to one of the remote speakers it can overload the output of the IMA3303 which could cause Q410 to fail.
I will be setting up this scenario on the work bench to see if I can replicate the failure.
Cindy & Christopher
Are Amplifier Failures are becoming common problem?
This past week I had another IMA3303 delivered to the shop with a failed amplifier. This IMA3303 was only 2 years old and the owner had just moved into the home, so there is no real history about the system.
The complaint was simple, nothing worked and the system just had a loud hum everywhere.
What I found was a IMA3303 with a failed amplifier. This time the failure was somewhat more dramatic than the last 3 units that have had this problem.
There were several burnt up resistors, including the pair of 2-watt resistors. One small resistor that is mounted under the heat sink actually looked like it exploded or flamed up.
It left a interesting fume patteren on the bottom of the heat sink.
This resistor seems to have been very hot for a long enough period of time which caused the solder pads on the back side of the board to become unglued from the circuit board. It was necessary to solder in jumper wires to makeup for the damaged pads.
Another difference with this unit was that one transistor actually failed and had a chunck of its case blown off. A transistor has to become very hot for this type of damage to occur.
In the end there were 5 resistors, 5 transistors, 2 voltage regulators, 1 diode and 5 capacitors that were replaced to reapir the IMA3330 and insure proper operation.
I also added a heat sink to the primary voltage regulator to provide some additional thermal relief to the regulator.
Just to be clear, this type of failure is not a power supply issue. It is most likely caused by the output of the amplifer becomming shorted. The short would most likely be in one (or more) of the cables that run from the IMA3303 Master Station to the remote stations.
In the next few weeks I will be rebuilding one of my shop IMA3303's and setting it up to see if I can make it fail in the same way as this unit.
Cindy & Christopher
Here are just a few pictures of an overheated voltage regulator on the Power Supply section of a IM3303 Master Station.
You can see that the circuit board has become dark brown (red arrow) from the heat of the Voltage Regulator. If you look carefully at the white substance (blue arrow) on the voltage regulator, it has cracked from the exposure to the heat.
This IM3303 was non-operational when it was delivered. The complete power supply circuit was rebuilt and this IM3303 came back to life.
Reader Comments (99)
I have trouble on my 3303 (installed in 1999) where the intercom button on the master unit seems to intermittently not connect. Pushing hard will sometimes connect but then it will stop transmitting in the middle of a sentence. sometimes work and sometimes doesn't.
Any ideas on how to fix this?
Thank you
Hi Doug,
Your IM3303 has a common problem with early production units. The solder joints on the intercom switches crack, causing intermittent operation of the pushbuttobs. This can be repaired, however it requires the IM3303 to be completely disassembled to get to the switches. It is probably not a do-it-yourself repair. You can certainly send the IM3303 to me for repair.
Thanks
Chris
I have a pretty new IMA 3303 and all I get is transformer buzz through the system and nothing else. Everything lights up but no sound.. Any ideas?
The problem you describe is to general to offer any specific ideas as to what the problem may be. Some trouble shooting will need to be done to identify what the problem is. You should call me to discuss what needs to be done
Thanks
Chris
My radio keeps coming on and the error code "IC" shows up and I cant do anything until I go to one of the other stations and hit the inside talk button. This allows me to turn the unit off until the whole things happens again 5 seconds later.
Hi Greg,
There are several things that can cause your IM3303 to be lock into the IC mode.
One common cause can be a wet, corroded or damaged outdoor Patio Station. If you have Patio Stations as part of your system, try disconnecting the 3- wires from the back of the speaker (don't let the wires touch each other) and see if the IC problem goes away.
An Inside Station can cause the IC problem, just like a Patio Station does, however it is less common for it to be an inside station.
The IC problem can also be caused by a damaged or shorted wire between the Master Station and a Remote Station. This is more difficult to track down.
There can also be problems with the IM3303 itself which cause this problem. All other sources for the IC problem should be eliminated before blaming it on the Master Station.
If you fill out an "Intercom Repair Request" form (in the navigation heading) I will contact you directly about troubleshoot the IC problem
Thanks
Chris
Chris, I have a client that is flipping a house. The IM 3303 system was install in the house. A day after closing someone broke in a attemped to steal the unit.
The master station was pulled out and speaker wires were cut with about a foot from terminal board. I have reinstalled the unit but don't pick up any radio stations.
The door chime works. When you press the talk button in other rooms you hear the master station click but no sounds come thru. I've looked over the entire back
for any loose parts and bad sodders. Yet nothing, let me know if there is anything you can think of that might help. As I believe I've done all the right things just possible
that the master station is broke do to improper removal.
Thanks, Omar
Hi Omar,
There are many possible causes why the IM3303 system is not working correctly. You should fill out an Intercom Repair Request Form (under the Navigation Heading) and after I receive it, I'll contact about how to proceed.
Thanks
Chris
Hi Chris, I recently bought a 12 y/o home that has an IMA 3303 system. The local NuTone service guys have been out to this house a couple of times with the previous owners and know the system well. They told me the main board was destroyed in a storm shortly after it was put in. The original owners didn't get it fixed. Now they tell me they can't get parts to either fix or replace the board. Like you've mentioned in a previous post, I am seeing "new" IMA 3303 master stations for sale for $900-$1,000. I was considering buying one of these since I have all the stations in many rooms in the house and outside on the patio with several outdoor speakers. I was hoping I could use some of this equipment rather than gutting it all and starting over.
I'd appreciate any suggestions. I looked at the compatibility program on the website and all options essentially had me replacing almost everything but the wire.
Thanks,
Kyle
Hi Kyle,
I understand that a local NuTone person has come out to look that the system, however was the IMA3303 ever removed and taken to the shop to see what's really wrong with it?
Not all problems are Micro-Controller related and without looking into the issues with your IMA3303, assuming the problem is with the micro-control is just a guess.
If you are interested in finding out if the unit is repairable or not, you can fill out an Intercom Repair Request Form (under the Navigation Heading) and once I receive it, I'll contact you directly about your IMA3303.
Thanks
Chris
I have an IM-3303 that was installed in about 1995.
We bought the house in 2010 and the system was basically working then.
Since then the system has slowly stopped working.
First the remote speakers stopped and now the door bell has stopped.
I can hear relay noise (clicking) but that is all. All functions have stopped. There is power and the clock works. That is about it!
I can not find any NuTone service in the area where I live (Greensburg, PA)
Any suggestions?
Hi Ron,
The problems with your IM3303 are to general for me to give you specific things to check. It would be easiest if you fill out an Intercom Repair Request Form (under the NAVIGATION heading) and once I receive it, I'll contact you directly about the problems you describe.
Thanks
Chris
Hi chris,
I just moved into a house that has an ima 3303 installed. There is a base unit downstairs with remote panels at the front door, loft and each of the 4 bedrooms. Unit was installed during construction in 2004. The main unit lcd display is lit up and will show the time and radio stations when scrolled. When I select AM, FM , door talk etc.........I can hear relays switching. But nothing happens. No radio sound or intercom. I looked through all your information and tried the reset button but that did not work. I unscrewed the main unit and I could not smell any "burnt" wiring or electrical components. I also did a visual inspection and I didnt see any loose connections or anything out of the ordinary. I didnt go as far to unscrew the stacked boards, but if something fried I would expect to smell it. Any ideas?
Hi Bob,
There could be many things wrong with your IMA3303. The last bit of troubleshooting you can do would be to unplug the Master Station from the Terminal Board. This will isolate the Master from the remote speakers and their wiring. If the Master begins to work correctly, you probably have a short in one (or several) of the wire runs to the remote speakers.
If you live in an area that has frequent storms with lightening, you might have a Lightening Damaged unit. You may also a a more common failure of some type.
If the problem has not been resolved after you have completed the last bit of troubleshooting, fill out an Intercom Repair Request Form and when I receive it, I'll contact you directly about the problem
Thanks
Chris
Thank you Chris. Will let you know. I appreciate the information.
When I push the Inside talk button on my Master Station, it feels like it gets stuck or it sounds like the relay is switching on and off. Is this the button itself and the contacts a dirty or is it the relay itself? I know there are four relays. Do each of them hanlde a set number of remote stations?
Hi Jim,
From your description, it could be the switch, it could be bad solder points where the switch is connected to the circuit board, it could be a relay problem (if it's a relay problem, it will happen when the I/P Talk button is presson a remote station) or it could be a problem in the ciruit that controls the relay.
Chris
My Nutone intercom model 3303 was installed when we had our home built in 1997. Just recently it has emitted a loud buzz (call it more or a foghorn sound) once in a while. Turning the sound off eliminates this. It only happens occasionally. What on earth could the problem be? I don't want to turn the sound on and have it wake me up at night!
Hi Claire,
There could be many things that are causing the problem you describe. It will take some basic troubleshooting to narrow down the likely cause. If you fill out an Intercom Repair Request Form (in the Navigation Heading) I'll contact you directly to discuss the problem and explain how to determine what's wrong.
Thanks
Chris
Hi i have nutone 3303 and everything works exept there is very little sound coming out of master station when i try play any radio station, i tried to turn it up all the way up but with no success, the sound is very poor and quiet.any suggestions would be much appreciated thx
Hi Jerry,
Is the low volume and poor sound quality just at the Master Station or does it affect the remote speakers as well?
Chris
Hi chris the low poor sound affects the master station and the remote speakers but only on fm setting. Am program as well as cd/tape and aux is nice and loud. Bad fm antenna maybe?
The same antenna is used for both AM and FM so it's unlikely that the antenna is the problem, you should make sue that the antenna is actually connect to the IM3303 and that it was installed up in the attic and dropped down into the wall.
Barring any installation issues, I would think you have a tuner or tuner circuit problem
Thanks
Chris
I recently purchased a home built in 1997 with an IM3303 system seems to work okay except some of the remotes have no sound.
I've switched them with a unit that does work and they work okay. So the problem lies within the unit. Maybe the speaker? Any known
Problems with these units?
Dennis,
I would clean the volume controls and switches in the remote stations that are not working to see if that correct the problem. You can check the solder connections where the push button switches are soldered on to the circuit boards (sometimes they will crack) You can use an ohm meter to check the speaker impedance (it should be around 25 ohms)
Thanks
Chris