The 10 most common problems with a NuTone IM / IMA4406 Music Intercom System
Saturday, December 1, 2012 at 10:33AM NuTone introduced the IM4406 in 1996 and it replaced the very popular IMA4006. By 1996 everyone was ready for a new top-of-the-line model and NuTone hit a home run with the IM4406.
The IM4406 included a powerful 20 watt amplifier along with AM & FM radio, and for the first time, a single disc CD player was built into the master station. The IM4406 featured “hands-free-reply” intercom operation and remote music control from every station. Probably the only complaint I heard about the IM4406 was the additional cost over the IMA4006.
One concern was the size of the IM4406 because it was 1-1/2” taller than the IMA4006. NuTone learned back in the 1970's that homeowners don't like large master stations, but the additional size was necessary to accommodate the CD player.
There are 3 different variations of the 4406, however the models are labeled as if there were only 2 variations. The original IM4406 was produced from 1996 through about 2002, then the IMA4406 was put into production.
There are actually 2 variations of the IMA4406 and it seems that sometime around 2005 the electronics were updated without the benefit of model number change. This “3rd” model may have corresponded with the change of which factory manufactured the masters.
First I will focus on the original IM4406:
The IM4406 was and has been, a fairly trouble-free model since its introduction. There were the typical new model issues which were mainly CD related problems. Many of these “problems” were associated with the CD player getting contaminated with dirt and sheet rock dust during the construction of a new home. There was also some confusion with the types of CD's that the IM4406 could play.
The IM4406 could play all commercially purchased CD's without any problems, but if you remember back in those days people were just starting to “burn” CD's on their computers and the IM4406 had problems reading these homemade CD's. There was also a rumor that the IM4406 could play MP3 files that were burned on homemade CD's, which was not true.
Unfortunately, the CD player assembly for the original IM4406 is no longer available and there doesn't seem to be any reasonable repair option for the original player. The original CD player assembly was manufactured for NuTone by a vendor which made CD player assemblies for many different companies. As with all modern manufacturing, once the demand for the assemblies is gone, the vendor stops production of the units.
There are basically 2 problems that occur with the CD player:
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The motor that moves the lens (which reads the CD) will fail and the lens just stays in one spot. While this is a small part, it is not possible to purchase replacements from the original vendor.
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All CD players will eventually develop a problem with the laser that reads the information off the CD. The laser beam will become weaker and weaker over time and finally it will become so weak that the reflection off the CD is not strong enough to be read. Again, without an exact replacement from the original vendor, repairing this problem is not possible.
(The original IM4406 CD Player Assembly)
Since the use of CD's has diminished a lot since 1996, the best and most popular solution with our customers is to abandon the CD all together and add a miniature input jack to the side or bottom of the IM4406. This jack can be used for any MP3 player (iPod or iPad) or an external CD player. This jack can also be used to connect a satellite radio receiver (XM or Sirius).
Power Supply Failures:
A new problem that seems to be developing with the original IM4406 is the failure of the power supply circuit on the Power / Amplifier circuit board. This should not be confused with the 2 low-voltage transformers (model 801T's) that are mounted in the IR105 Wall Housing. (Caution: The 801T transformers have built-in internal fuses, if the output of the transformers is shorted, it will blow the fuse and the transformer will go dead. The fuse is not replaceable and a new transformer will need to be purchased!!!)
The first sign of trouble with a failing power supply on most NuTone Intercom Systems is an increase in the background noise of the system. All NuTone Intercom systems had a certain amount of background noise which could be heard if you listened very carefully with your ear up against the speaker. This light “hissing” sound is called “white noise” and it's the sound an amplifier makes when it's turned on.
This background noise was eliminated with the introduction of a new intercom platform in 1994. All of the NuTone models produced from 1994 through 2008 were designed with a “stand-by” mode. When the intercom system was not in use (not listening to music or using the intercom) the amplifier will switch off and the system became silent, no more background noise.
Since the IM4406 has a “stand-by” mode, when the power supply begins to fail, a homeowner will not hear the increase of the background noise of the system. It's not that the increase isn't there, it's just that since the system is in “stand-by” you can't hear it.
The first symptom a homeowner may notice is a random “static” or “crackling” noise from the speakers even when the system is in stand-by. There may also be a loss of volume with the music and door chime. Most of the calls we receive are when the IM4406 is at the point of failure and nothing is really working except the clock.
(Pink arrows point to voltage regulators)
The power supply in the IM4406 is a modern design and it uses components to create many different electrical voltages, which are used to power different parts of the IM4406 master station.
(Aluminum Heat Sink for the Power Module)
Most of these power regulators are mounted to the massive aluminum heat sink on the back of the power module. However there is one regulator that is not mounted this way; it is just mounted flat against the circuit board.
(voltage regulator removed, dark area on circuit board caused by excessive heat)
Over time, and while the values of other supporting components drift, this regulator will start to run hot. Over time it will continue to get hotter and hotter, and since the regulator is not mounted on the heat sink, the excessive heat it generates has no place to go and the regulator fails.
I have seen units where the regulator could be pulled off the circuit board with your fingers because the solder connections had failed due to the long term exposure of the heat. When this regulator fails, the IM4406 stops working.
Luckily, repairing this problem is very straight forward, but for a long lasting repair more than just a new regulator will be needed. All of the supporting components in the power supply circuit should be changed and the primary capacitors should be checked and replaced as needed.
There is also a modification that should be done to improve how the regulator is mounted in the power module. This modification is based on a change that was made in the final version of the IMA4406.
An aluminum bracket needs to be fabricated and the regulator needs to be mounted to one end of the bracket. The other end of the bracket is fastened to the metal covering of the large aluminum heat sink. This gives the heat that the regulator generates a path to the large heat sink. This modification keeps the regulator operating temperature well within the normal range for this component.
These types of voltage regulators are available with different power output ratings, for different applications. We use a replacement regulator which has a higher rating than the original component and it also has a different case style, which works better to transfer the heat away from the component.
The original regulator has an all plastic case and the replacement has a case with a metal backing plate to aid in the transfer of the heat. Since the metal backing plate is conductive, it is necessary to use a insulating transistor mounting kit when attaching the regulator to the bracket. Without this kit the regulator will fail quickly.
Along with the regulator replacement and bracket modification, there are 6 capacitors and 4 diodes that will also need to be replaced.
The power supply circuit for the IM4406 includes 7 larger capacitors. These have not been a big problem on too many IM4406 Master Stations, however there have been a few units in which these capacitors have failed. It's a good idea to check these capacitors with an ESR meter and evaluate their condition. If they show any signs of increased resistance, they should be replaced.
When the repair of the IM4406 is completed, the power supply circuit should last longer than the original design. The IM4406 may be the high point of NuTone Music Intercom System design and it certainly is worth keeping it in good working condition.
See all of the IM4406 pictures here.
Cindy & Christopher
A Toasty IMA4406 was delivered to the shop today!
I know that I've already done an IMA4406 power supply rebuild article but I really think this IMA4406 will be an interesting repair.
This IMA4406 came from a customer in New York with the following description of the problem:
"This IMA4406 is 7-8 years old and within the last 2-3 months it has begun to work erratically and now it continually show "IU" on the display."
I was very surprised when I opened the box and found the plastic heat sink cover to be so discolored. I have repaired lots of IMA4406's and I have never seen anything like this.
You can easily see how discolored the plastic is compared to a normal looking IMA4406. I don't think the discoloration is from where the master is installed because the plastic cover over the CD player is still clear. It seems to me that this unit must have been very hot for a very long time to end up like this.
The area around the voltage regulator is discolored and the regulator is somewhat loose on the board.
Tomorrow this unit will be on the repair bench, I can't wait to see what it's really like when its powered up.
More to come. . .
Thursday, March 14th
I put this toasty IMA4406 on the bench today and nothing looks good at this point. The power supply / amplifier module is toasted and the master is cycling on/off, on/off, on/off while the display just shows "IU"
I temporarily replaced the power supply module with a known good module and I swapped out the main control board with another good board and the constant "IU" problem on the display and the cycling went away, but there is no radio from the speaker in the master and the Intercom operations are all wrong.
I also noticed that the LCD display was lit unevenly, with some segments dark and other segments look much lighter and the seem to flicker. As I stripped the IMA4406 down, removing each board and inspecting them, I found one set of resistors in the display circuit are discolored from heat.
I got the go ahead from the customer to do more diagnostic work on this master.
More Tomorrow. . .
Wednesday April 17th
This IMA4406 is finally complete. It had so many problems that it was necessary to install substitute circuit boards to help narrow down the problems board by board.
The Power Supply Module was the simplest part of the repair and I actually rebuilt it last, after making sure that all of the other problems could be solved. A new voltage regulator mounted to a new heat sink bracket and some new capacitors and diodes put the power supply back into good working order.
The Main Control Board had the most problems. While the customer did not report any power surge or lightening issue at his home, I suspect that one of those situation caused some of the damage I found.
There were logic problems with the intercom control circuits; there were two failed voltage regulators on the board, the op-amps for the chime inputs produced a distorted sound and the AM/FM tuner and some of the supporting integrated circuits had failed.
This is a lot of damage to have on just one board. A symptom of these problems was the massive overheating of the power supply module. I used a temporary power supply module while I was working on the control board. The power supply would heat up very quickly, so hot that the components could not be touched. This was caused by the failed circuits on the main board drawing to much current and over taxing the power supply.
Once the main board was repaired, the overheating power supply problem went away.
The Processor Board had just a few problems, there were some over stressed resistors for the LCD display and a few logic IC's that needed to be replaced.
The CD player did not function after the rest of the IMA4406 was repaired. This may not be related to all of the other problems. The CD players in IMA4406's have always be a troublesome and it is likely that it failed at an earlier date.
The last issue was with the plastic faceplate itself. After being exposed to a great deal of heat for a long period of time, the plastic has become very brittle. There are many small screws that attach the circuit boards to the back of the faceplate and these screws thread into standoffs on the faceplate.
These standoffs are now so brittle that the screws just shatter the plastic when they are installed. I used some hot glue inside the screw holes and around some of the boards to help reinforce everything and hold it together.
In the end, this was a successful repair, oddly enough about a week after this was delivered to us I had another IMA4406 show up in almost exactly the same condition. It leads me to believe that if a failed IMA4406 is left unrepaired for a long period of time (or a short time with a dramatic failure) it will be more severely damaged than average.
Cindy & Christopher
Here are just a few pictures of an IM4406 with a more extensive power supply failure.
You can clearly see the crack in the voltage regulator. This was likely caused by either the regulator being severally overheated or perhaps that this IM4406 had all of the signs of a failed repair attempt. One giveaway is all of the Thermal Compound (the white stuff) under the power supply components. There is easily 10 times the amount of Thermal Compound that is needed. I also found that the Power Supply Module had been disassembled prior to the Master Station being shipped to us.
Since there were so many unknowns about this IM4406, I decided that a complete Power Supply rebuild was in order.
The board was depopulated and all of the components were replaced.
Reader Comments (69)
I noticed on the schematic a notation of 3P, 12P etc and wonder what that is pretaining to.
Thanks
Larry
K&L Electronics
Hi Larry,
I am not sure exactly what you are referring to on the schematic.
Thanks
Chris
We have a NuTone 4406 CD/radio intercom system. Our neighbor's house was struck by lighting. Although we never lost power, several circuit breakers and GFI's were tripped. The NuTone system now does not work. Appears that there's no power to the master station. I opened it up, and nothing looks "ffried." Is there a fuse mechaniism that Ishould check? Is there a trouble shooting guide?
Thank you.
Hi IKevin,
Please fill out an Intercom repair Request Form (last link in the Navigation section) and once I have received it, I will contact you regarding the problems with your IM4406
Thanks
Chris
Hi Kevin,
Please fill out an Intercom repair Request Form (last link in the Navigation section) and once I have received it, I will contact you regarding the problems with your IM4406
Thanks
Chris
Hi Chris, our in house IMA 4406 has a blank (lit and powered) screen - and the entire system is unresponsive. No numbers or letters present - just lit. No aspect of the devise appears to be working - intercom, radio, CD player are all blank. What can I do please?
Hi John,
You can try resetting the Master Station by using the reset push button. Open the Right Hand Door on the bottom edge of the IMA4406 Face Plate. The first switch on the panel is the Loudness Switch. Just to the LEFT of the Loudness Switch, and slight below it is a very small hole in the panel. Inside the hole is the RESET BUTTON. You will need a small screwdriver, insert the screwdriver into the hole and push and hold the RESET BUTTON for 5 seconds. The actual REST BUTTON is a Micro Switch and it will make a CLICK noise when you push it.
After you release the RESET BUTTON, the clock should be flashing (12:00 or 1:00) rest the time and try the radio, intercom and CD player. If everything works then your'e done. If the RESET did not solve the problems, please fill out an Intercom Repair Request Form (in the Navigation Heading) and I will contact you directly about the problems with your IMA4406.
You can also download a copy of the IMA4406 Owners Manual, which shows where the RESET Button is located.
Thanks
Chris
My IM-4406 master went dead following a storm. The speakers in the master and the room units had a whistling tone. The original installer said the unit needs to be replaced. My wife said the installer unscrewed the front panel and may have tried to reset the unit. I spoke with the installer and he said it was not either of the two transformers. I would appreciate your thoughts.
Hi Sonny,
During the storm was there a lot of lightning and were other electronic items in your home damaged? If the answer is YES, then you may have lightning damage in your IM4406. If NO then you may have a more general failure from a normal power line voltage surge or something like that.
If you fill out an Intercom Repair Request Form (Under the Navigation Heading) Once I receive it, I'll contact you regarding your IM4406
Thanks
Chris
Hi Chris - First, thanks for posting some great information! I replaced our original NuTone radio-intercomm (circa 1979) in the mid-90s with an IM4406 and new speakers. The IM4406 sounds just as bad as its predecessor,.... scratchy sound on both bands of radio, and CD. I was considering replacing it again, but have no faith in NuTone products, or their tech support. I have been unable to find a suitable/affordable alternative. Any advice?
Many thanks,
John
Hi John,
If you installed the the IM4406 Master Station and Speakers in 1995, your system is now almost 20 years old. I would guess that it worked well and correctly after it was installed and at this point it probably just needs some general maintenance to bring it back into good working order.
Cleaning the speaker switches and volume controls will solve many problems with most systems, if there are any more specific problems with your IM4406, they can be dealt with also.
The IM4406 is possibly the last, best Music Intercom System that NuTone made, and even the best equipment will require some attention when it is nearing 20 years.
If you need further information about getting your system back into good condition, please call me directly.
Thanks
Chris
Hi
I have a NUTONE IM4006 (with a cassette player) which was installed in 1990. It has been a great little unit until recently. All 9 inside speakers as well as the 3 door speakers are working. The AM/FM radio as well as the clock does not work, with the clock occasionally displaying a “0” or a “1”
when the “RADIO” switch is in the “off” position. When the “RADIO” switch is in the “on” position the clock display is blank. There is 24 VDC at the output end of the transformer. I read another post from you that mentions a RESET BUTTON next to the LOUDNESS SWITCH but there is no visible RESET access hole on the unit. Any suggestions as to what my problem(s) might be and where the reset might be hidden?
I appreciate your help,
Doug
Hi Doug,
The IM4006 System uses a 16 volt transformer, so you system made have been installed with the wrong transformer. I have seen this happen on other installations, especially when the IM4006 was an update of an older 6-wire system like a Model 2540 which used a 30 volt transformer.
Based on the description of the problems your IM4006 has, there is something very wrong with the Master Station. Without knowing more about the system, I would only be guessing about what is wrong with it.
Please fill out an Intercom Repair Request Form and once I receive it, I'll contact you directly about your system
The Repair Request form is located under the Navigation Heading on every page
Also, The IM4006 does not have a reset button, only the IM4406 and IMA4406 have rest buttons
Thanks
Chris
how to connect miniature input jack to im4406 and where to get it.
Hi Jan,
If you do a search for Audio Jack in the search box, you will find the article about adding an audio jack. The parts to makeup the jack are available at Radio Shack, or you can buy it assembled from us.
Thanks
Chris
I have a dear friend who has an IM4406 and the CD player doesn't work any longer. I see above you mention adding a mini jack as an aux input and circumvent the CD player all together. I love the idea as they are more inclined to use an MP3 player. I know this sounds counter to your repair business... but, do you have any plans, instructions, etc. that would illustrate how someone could accomplish this?
Thank You in advance for your input.
regards,
Hi Aaron,
We have instruction on this site about how to add an audio jack to any NuTone Intercom Master Station. If you use the "search web site" function and search the terms "Audio Jack" you will the proper pages.
Actually this type of modification is not counter to our repair philosophy, when it is no longer possible to repair any unit to it's original condition, due to lack of parts (which happens more and more often with newer equipment) a clean, well thought out modification that adds value to the unit is the correct choice.
Thanks
Chris
The CD PLAYER HAS STOPPED SPINNING THE DISC ON MY Nutone 4406. Can this be fixed.
Hi Earl,
It depends on which version of the 4406 you have. If you have a IM4406, then no it cannot be repaired. If you have a IMA4406 then yes, the CD player Repair Kit is still available.
Please let me know which version you have
Thanks
Chris
I have the newer model Nutone system you refer to. How can I get in touch with you to repair the turntable which does not spin. Everything else is working, AM FM radio, clock, etc. How do i contact you or someone you would recomment to service my
Nutone player? Thank you. Susanne
Hi Susane,
Thanks for sending us a Intercom Repair Request Form. I'll be calling you today to discuss the repair of your IMA4406.
Thanks
Chris
I installed the audio jack in my IMA4006 as you described and it works and I do get sound but it gets very distorted at even medium volume levels. This does not happen when in radio or cd mode. Is there a way to Address this? Thanks for all your help..this is a great site you provide.
Hi Nathan,
When you connected the audio cable did you plug it into the Tape or Phono input? It should be plugged into the Tape Input.
What type external music source are you using? If the external source has an adjustable output, it may be set to high. Some inexpensive MP3 players have very weak output signals because they are designed to only drive ear buds. In these case if you have the volume maxed out, there is much more distortion.
Thanks
Chris
The "Door Talk" feature keeps going on and off. When it goes on, I can hear the outside sounds throughout the house. It stays on for a few seconds, goes off, and then on again.
Hi Carol,
Without more detailed information about your system and this particle problem, I can only make an educated guess as to the source of the problem.
My first guess is that you have a short in one of the 6-wire cables that run from the Master Station to the Remote Stations. The short acts like someone is pushing and releasing the "Door Talk" button.
The other possibility is that your Master Station has developed a problem and the Door Talk function is self activating (although I haven't ever seen this happen).
If you want to try some basic troubleshooting, do the following, in the order listed:
1. Download the Installation Manual for your Model from the "NuTone Intercom Installation Manuals" page.
2. Familiarize yourself with the way the remote station siring is connected to the Terminal Board.
3. Familiarize yourself with the 5 cables that connect the Master Station to the Terminal Board.
4. Open up the Master Station.
5. Unplug the 5 cables that connect the Master Station to the Terminal Board, from the terminal board. If the problem stops (give it some time to be sure) this is a good indication that there is a wiring problem with one or more of the 6-wire cables to the remote stations. If the problem remains, you have a Master Station Problem
6. If you determine you have a 6-wire cable problem, disconnect all of the 6-wire cables from the Terminal Board
7. Plug the 5 cables that connect the Master Station to the Terminal Board back into the Terminal Board.
8. Verify that the problem did not return after step 7
9. Reconnect each 6-wire cable, one at a time, until you find the 1 (or more) cables that cause the problem. Leave the "bad" cables disconnect.
10. Report back to me after you complete steps 1-9
You can also fill out an Intercom Repair Request Form and after I receive it, I'll contact you directly about this problem.
You can also call me to discuss the problem.
Thanks
Chris
925-743-8236