Common Problems with the NuTone IM / IMA3303
Friday, February 8, 2013 at 7:34AM NEW IM3303 Loaded with convenience, Simple to operate, Styled for Today!
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)
Hi Al,
Please do the following:
1. STOP - Don't do anything else until we discuss this by phone. This should be fairly simple to figure out, it's just to involved to cover in a written response.
Please call me on Monday, or when it's convenient for you.
Thanks
Chris
925-743-8236
My Nutone IMA-3303 is stuck in a blinking 1:00 loop. I pressed the reset button several times but no luck, Any suggestions?
Hi Jerry,
Other than the clock blinking, what else works or doesn't work?
How long has it been like this?
Please let me know
Thanks
Chris
Hi Chris,
Have a model 3303 and have been trying to trouble shoot. Chime not working. Radio or intercom not working.
Panel clock is OK. Each station will click when buttons are pushed as will the master. Power light comes on at master when you press fm or am
Is this a transformer issue? Could it be both transformers?
Thanks,
Tom
Have a Nutone 3303. Was working somewhat ok - never great. Recently we noticed door chime not working and then checked to find the radio and intercom not working. Clock is working. Each station has clicking sound when you depress button but no intercom voice or sound working.
Is it transformer(s) or amplifier or other? Get a little hum when putting on a radio station. We're second owners, but think the unit is about 10-11 years old.
Thanks
Tom
Hi Tom,
Based on your descriptions, it sound like your NuTone IMA3303 probably has a failed Amplifier , failed Power Supply or possibly both. Since you stated that it "never worked great" I suspect that this has been a on going problem and the Master Station has finally failed.
It is unlikely that either transformer is bad and they are the source of the problems.
If you fill out an Intercom Repair Request Form (located under the NAVIGATION HEADING on every page of this site) once I receive the Repair Form, I'll contact you directly about the repair of your Master Station
Thanks
Chris
925-743-8236
This house was built in 1990 with Nuton IM-3003 system installed, and I bought it and moved in 1994.
The master unit was degrading over time, beginning with low humming noise even with no radio on, and intercom stop working.
Now it became totally dysfunctional, not even radio. But display works and ever present faint humming noise. :-(
I cannot find any documents nor troubleshooting guides. I hope you can help or lead me to right direction.
Sincerely, from S. TX
Hi Don,
If you look under the index heading "NuTone Intercom Problems by Model Number" and click on the very first choice "NuTone IM / IMA Series Music Intercom System" the link will take you to the main Index
where the IM3003 is one of the choices. You should find at least 99% of the answers to your questions about what has happened to your IM3003 System
Thanks
Chris
Subject: IM3303 Chiming constantly Message:
Hi Chris,
Found your really helpful web site after our IM3303 started chiming constantly earlier today. We tried to push the button outside the front door (which is the only station that can invoke the chime) repeatedly in case it was stuck but that didn't seem to do anything. The only thing that made a difference was on the master station to push the ‘door talk’ button which silenced the chime for a short period of time (perhaps 30 seconds?). During that time, it didn't seem that talking at the master station resulted in anything being heard at the front door. Also, if the ‘end call’ button was pushed on the master console (after the ‘door talk button’ and before the talking period, 30? seconds, ended), the chiming would resume immediately. We've turned down the volume at all stations so we don't hear the constant chiming but even now, after several hours, when we turn the volume back up, we can hear the chiming continue.
Any suggestions on next steps for troubleshooting?
Thanks in advance.
Dave.
Hi Dave.
There are 3 basic parts the Chime Circuit in the IM3303 System
1. The exterior Pushbutton
2. The Chime Module inside the IM3303 Master Station
3. The Pair (2-wires) of Wires that connect the Pushbutton to the Chime Module.
Do the following:
1. Remove the Door Speaker Station from where it's installed on your Front Porch. Disconnect the wires from the screws on the back of the Pushbutton.
If the Chime stops ringing, replace the Pushbutton. If it does not stop ringing, go on to step 2
2. Open up the IM3303, locate the Chime Module (watch our Video "how to remove an IM3303 master Station, watch from time 5:20 for Chime Module information) disconnect the wires from the chime module.
If the chime stops ringing, you have a wiring problem ( there may be an easy workaround for this) if it does not stop working, go to step 3
3. On the left-hand edge of the chime module, there is a 1/2" wide, flat gray ribbon cable. Follow the ribbon cable (going to the right) until you find the other end.
On the end of the ribbon cable there is a white connector, which is plugged into the main circuit board on the IM3303, unplug it.
At this point the chime will stop because it is disconnected. At this point we are 99% certain that the Chime Module has failed.
You can send it to use for repair or replacement, in the case that it is not repairable.
If you have any questions, please call me 925-743-8236
Finally, you must do something about this problem soon, otherwise the IM3303 can be damaged from the constantly ringing chime
Thanks
Chris
I have a Nutone IM3303 system installed approximately 1994. It has a wall mounted door chime in an interior hallway that rings faintly when the front door speaker button is pressed. Is the wall mounted chime unit replaceable? Can it be replaced with any 3 wire chime unit such as those available at Home Depot or Lowe's? If the transformer is failing, where is that transformer located? At the front door speaker or in the master control unit?
Thanks.
Hi Bob,
I have some questions:
1. Is the chime in your hallway a NuTone Chime?
2. Is it a standard 2-note "ding-dong" chime or is it a musical chime that plays different tunes?
3. When it was working, did you only hear the chime in the hallway or did you hear it through the IM3303 System also?
The direction to go in will depend entirely on the specific details of your original chime
Please let me know.
You can also email me pictures of your chime: nscompany@msn.com
Thanks
Chirs
I have a IM-3303 System with a Doorbell addition. When the Doorbell is rung it does not ring inside the house but loudly rings outside the door that the Doorbell is activated. Is there a way to fix this problem. Out guests are getting a loud scare when they ring the Doorbell.
Hi Joe,
If your IM3303 Systems has a Chime Module and it is heard through the entry door speaker, your IM3303 has a problem.
This type of problem is not something that the average person would be able to repair themselves.
If you're interested in have your IM3303 repaired, please fill out an Intercom Repair Request Form (located in the left-hand navigation bar) and once I receive it, I'll contact you to discuss the problems with your IM3303 and its repair
You can also call me if you'd like
Thanks
Chris
925-743-8236
Intercom is working, clock works, radio tries to tune to different stations, but no music, and doorbell stopped working at both front and back door. Any suggestions? I would really like to have it working again. Maybe the transformers need to be replaced?
Hi Karen,
The very first thing I would try is doing a Reset on the Master Station. If the rest does not solve the problem you will need to do some basic troubleshooting to determine if the problem is within the IM3303 Master Station or if it's being caused by some problem with a remote station or wiring.
We have several Videos on on YouTube Channel that may help you: https://www.youtube.com/playlist?list=PLsTvqKsBnGYc2zj1Db43FzJR_JV684dsi
If you determine that the fault is within the Master Station, it will probably need to be sent in for repair. It is very unlikely that the transformers are the cause of the problem. If the transformers are cycling on/off, it is typically a symptom of another problem, not the problem, not the problem it self.
You can fill out an Intercom Repair Request Form or you can call me to discuss the problem further
Thanks
Chris
925-743-8236
Hi, Installed a IMA 3303 in my new home in 2009. Worked fine until now. The LCD is lite and their is nothing displayed. Nothing works. Help
Hi Stu,
Have you tried doing a Reset of the Master Station? If not, that would be the first thing to try. We have a Video on our YouTube Channel that shows how to do a Reset
If the Reset does not resolve the problem, please fill out an Intercom Repair Request Form and once I receive it, I'll contact you by phone to discuss the problem with your IMA3303 and its repair
You can also call me to discuss the problem
Thanks
Chris
925-743-8236
I have a Nutone IMA 3303, installed in the 90's (replaced the original unit that may have been hit by lightning). The master unit was removed from the wall during recent remodeling. Upon reinstalling it, it works fine except the chime is barely audible with the volumes turned all the way up. Pressing a doorbell button results in the radio muting for several seconds. I have tried resetting several times, no change in the problem. Any ideas?
Hi Steve,
Have you tried adjusting the volume level on the Chime Module? If not, we have a Video on our YouTube Channel that shows how to do this.
If that does not work, It may be a Chime Module failure, especially if your Chime Module was transplanted form the original Master Station, into the replacement IMA3303
There is always a chance that there could be a problem with the IMA3303, however if it was working normally when it was taken out for the remodel, it is not likely to be the source of the problem.
This is all based on the assumption that nothing happen to the IMA3303 while it was removed.
Please contact me if you need more help with solving this problem or if you need to have your Chime Module repaired
Thanks
Chris
925-743-8236
Chris,
good evening I have a nutone IMA-3303 WH my problem is the master volume whenever I turn the volume low or high the sound sometimes scratch and go out but when I try to move the master volume the sound will come on again sometimes loud sometimes soft what
could be the problem.
Thanks.
Joey C.
Hi Joey,
It sounds like the volume control is dirty and needs some cleaning. You should use some Deoxit D5 and use a little as possible in the volume control (like 1 or 2 drops)
If that doesn't clear up the problem, you may have a more serious problem.
I will put together a short Video and poet it to our YouTube Chanel showing how to clean the volume control
Thanks
Chris
Chris,
I have read through all of these posts, which are incredibly good. Here is my problem: My front doorbell/intercom no longer works. I had a repairman for the company that originally installed it 18 years ago out and he unscrewed it and tested it. it's dead and I need a new one. Do you sell replacement parts for the Nutone IM 3303. Everything works inside, the intercoms, the radio, the clock and the intercoms. I just need a new front door unit.
I love it and miss it, because it is so nice to say, "May I help you/", without going to the front door! I also purchased other chimes for the doorbell (Christmas music, Dixie, etc.)
Thanks in advance for your help.
Oh, I almost forgot, my patio one is dead too.
Thanks!
Renee
Hi Renee,
We do have both replacement parts to repair your original Entry Door Station as well as completely new entry door stations.
Installing there the parts to repair your existing station or installing the new station is easy, and I'm sure you can do-it-yourself
Please call our office to order the items your need, to solve the problem with your system
Thanks
Chris
925-743-8236
IM-3303 came on during the night. I C now shows and FM light is on all the time. How do I do a reset? We have a patio speaker as well and have been having lots of rain the past 2 weeks.
What do you suggest?
Thank you