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)
Hi Chris:
I am remodeling my kitchen and I have a im3303. The am radio reception was terrible before I moved it so I ran a fifty foot piece of 2/c 22awg and hooked it up to the two am terminals and switched the am selector switch. This helped some but the am stations are still too noisy to listen to on the system. Can you suggest anything I can do to increase the am reception to a listenable state. The area I live in is pretty hilly area and I know that is a problem but both of my cars get good reception on their radios.
Hi,
I have an older personal care home. There are 11 units and a master base station in the kitchen. After completing a kitchen reno, we reconnected the base station with the ribbon cables and wires to the transformers. The master unit worked for a few weeks, but then would turn off. Later, it would turn on again, work for a while, and go back off. Is this a common problem (that I'm hoping may have an easy possible solution)? Does it matter which of the two wires is connected to which of the two terminals on the transformer?
Thanks in advance,
Jason
Hi Don,
Radio reception, especially AM can be tricky. The best AM antenna is a single 22 guage piece of stranded wire about 40 feet long.
The wire antenna should be orientated to allow for the best reception possible in your area. Some areas have just terrible reception and there isn't any magic to solve this.
You can't really compare the intercom reception to your cars, automotive antenna have the benefit of using the metal in the car body as a huge ground plane, which greatly improves the reception.
Hi Jason,
Based on your description, it sounds like one (or possibly both) of the low-voltage transformers that power the IM3303 are shutting down. This is likely being caused by it over heating. NuTone transformers have thermal limiting devices built into them, to prevent them from being a fire hazard.
A transformers can overheat because it has an internal fault or because the device it is powering is demanding more current than the transformer is designed to supply (this is the likely cause of your situation)
The way to test this theory is to do the following:
Open the IM3303 and touch the transformers, if either one is more than just slightly warm to the touch, that transformer may have a problem
Measure the voltage on each transformer, they should read about 18 Volts AC on a volt meter, if either transformer has much less than 16-18 volts, there is a problem
Leave the IM3303 open and wait for the Master Station to shut down, remeasure the transformers voltages, if either one reads almost 0 voltage, that means the thermal limiter has shut the transformer down.
You could try just replacing the transformer, but I think the source of the problem is likely to be the IM3303 Master Station
Thanks
Chris
hello,
My intercom system is completely broken and we don't use it, with the exception of the doorbell that's hooked up to it, is there any way to bypass the main system but still have the doorbell work ?
thanks
mona
Hi Mona,
The short answer to your question is no. The door chime is part of the Intercom system and without a complete and working system, the chime will not work. Many repairs of Intercom Systems are simple and straight forward.
If you fill out an Intercom Repair Request Form (you can find the link under the Navigation Heading) once I receive it, I'll contact you about the problems with your system
You can also call me to discuss your system
Thanks
Chris
925-743-8236
ima-3303 system, 3 of the outside remotes not working, i inside remote working, door bell chime not working on any remote. thanks wayne
Hi Wayne,
Without additional background information about your system, it's difficult to answer your question.
Please fill out an Intercom Repair Request Form (you can find the link under the Navigation Heading) once I receive it, I'll contact you about the problems with your system
Thanks
Chris
I have a im-3303 and recently had power surges and now all I get is a 1c on the screen can any body help
Hi Joe,
Yes, we can help. Please fill out an Intercom Repair Request Form (in the right-hand column of the Navigation Section) section of each page. Once I receive the Repair Request, I'll contact you directly about the repair of your IM3303
Thanks
Chris
Hi, do you know what kind of resistor is used at R427 (the one that looks like it caught fire)? Mine seems to have disintegrated as well and now I can't identify it, nor can i find any schematics for this device anywhere.
Thanks!
Hi Tyson,
R427 is a 4.7 ohm 1/2 Watt Resistor. 5% tolerance. The burnt resistor is not the source of the problem that caused it to fail, it is a symptom of a larger problem. Simply replacing the resistor will not solve the larger problem. You must diagnosis the problem and solve it, otherwise he resistor will simply fail again.
Thanks
Chris
Thanks for the info!
You're likely spot on, I'm sure there are other issues with the board, so far, the following other parts look damaged from visual inspection:
C406: capacitor - 1000 mF, 35V
And the 4 transistors (power regularots, sound emps, not sure) hooked up to that super hot uncooled head sink:
B1016a (transistor?) -
C1568-R (transistor) -
D1407a (transitor?) -
7812A JRC M1028J (transistor?) -
Where do you buy these? I can't find the model #'s anywhere online.
Thanks again!
--Tyson
Hi Tyson
Finding the correct components can be difficult, we source many of them from suppliers in Singapore and other countries outside the USA.
I will caution you on trying to repair your IM3303 yourself. The circuit boards in these models use very small traces and pads, and when they have been overheated they can easily lift from the board, which ruins them.
If you are no familiar with work on electronics (component level) I would not recommend you try to do this yourself. The risk is high and if the board is damaged, finding the correct (and exact) replacement can be difficult and expensive.
Consider sending your Master Station to me for repair.
Thanks
Chris
We recently moved into a house in which a IM 3303 is installed. I can't seem to locate the CD or Aux inputs. Is there any chance you'd be able to give me some direction?
Any help you might provide would be greatly appreciated!
Hi, Peter
If you download a copy of the Installation Instructions fro your IM3303 (in the FREE MANUALS section of this site) you will find information about the auxiliary input jacks on Page 6
Thanks
Chris
Hi,
You're site is awesome and very informative. I have a 2001 IM3303 that I installed when I built my house. Over the years there have been three failures that have gotten progressively worse, and now we never use this useful feature of our home.
The first problem that appeared was that in about 2005, the individual speaker stations (5" speakers in 6 rooms, plus one surface mount on the covered patio) would crackle when adjusting the volume. This would happen for a few seconds, then, as if some static buildup was reduced, the crackling of that speaker would be done for a while. Then, maybe the next day, the speaker would be crackly again. This was only a nuisance.
The second problem was that while listening to the radio, all speakers including the master would have sudden drops in the radio volume then the volume would come back up right away. The doorbell chime sound didn't seem to be affected. Over time the volume drops were more frequent and long-lasting. Now it's pretty much always at the low volume level, so we don't use it.
The most recent problem is that the buttons started to fail on the master station. I first noticed it on the time adjustments, such as adjusting auto-ON and -OFF times. The failure was that the button command was not received by the controller. At first, I could keep repeatedly hitting a button until it would finally register, but now there is no response, ever. I can't even adjust the clock to fix the wrong time display.
I have been considering getting a replacement PC board, but I don't even know if the problem is related to that.
The functionality of the system now is that the bedroom remote controls can power up the system, but the sound doesn't really work. Many, if not all, of the master station panel buttons do not function. The doorbell chime works fine and we can go through the melody selections at the master station with no problems.
One other factor in the system is that it is mounted on an external wall of the house. The outside is shaded, and kept from the elements under the patio cover, but we are in the Phoenix area, and it made me wonder if the master unit suffered from the high outside temperature.
Thanks for your help!
Remo
Hi Remo,
From your description it sounds like the major problem with your IM3303 is either a failed amplifier, failed power supply or both. The static in the remote volume controls may be amplifier related or it could just be dirty volume controls.
The problem with the push buttons on the Master Station could be Power Supply related or again just very dirty buttons. I have worked on Master Stations from dry, areas and sometimes the push buttons will be affected by the dry, dusty climate.
Having your IM3303 installed on a outside wall way also be a factor in the push button issues.
You won't be able to purchase a circuit board for your IM3303, they are no longer available from NuTone and buying a used board is often just swapping one set of problems for another.
The best course is to have your IM3303 repaired.
Please fill out an Intercom Repair Request Form (located under the NAVIGATION HEADING on every page of this site) and once I receive it, I'll contact your directly about the repair of your IM3303
Thanks
Chris
925-743-8236
I have an older IMA 3303 unit in my home which seems to be working fine. The outdoor speaker at the front door, however, was not working so I purchased a new Nutone NDB300WH model speaker which I was told would be compatible with this intercom system. Unfortunately, the model did not come with installation instructions so I don't know how to connect the 4 wires. Is there a diagram which clearly shows which wires are to be connected to which wires from the wall? Thanks.
Hi Eric
Installing the new Door Speaker should be fairly easy if the original door speaker is still in place and the wires are still connected. I am going to assume that the original door speaker was the type that also has the door chime push button on it.
1. There are 4 wires behind the original door speaker that connect it to the IM3303 system. 1 pair of wires (2-wires) are connected to the actual speaker cone and the other pair (2-wires) is connected to the door chime push button.
2. If the wires are still connected to the original door speaker, all you have to do is swap the pairs of wire from their original locations (speaker cone & push button) to the same connections on the new door speaker..
If you have already removed the original door speaker and disconnected the wires (without labeling them as to where they were connected) do the following:
1. Many times the pairs of wires will be color coded (orange pair, black pair, red pair etc.) and the pairs will be twisted together. Sometimes this is not the case and you will have different colored wires all coming from a single cable( red, black, green, white etc.)
You will need to identify which wires make up the 2 pairs (speaker cone & push button) the easiest way to do this is to find out which pair is for the door chime first. By trying different combinations of wires together, you need to find the 2-wires that make the door chime ring. Try a logical progression with the different possible combinations (red & black, red & white, red and green, black & white, black & green, white & green etc.) of wire colors until you find the pair that make the door chime ring.
2. Connect the door chime pair to the door chime push button.
3. The remaining pair will be the door speaker pair. Connect the remaining pair tot he red and black wires that are already attached to the back of the speaker cone.
Two final tips:
1. There is a white plastic cover over the back of the door chime push button. This IS NOT WHERE THE WIRES FOR THE DOOR CHIME ATTACH. You must remove the plastic cover to see the back of the actual push button, The push button has 2 screws on it, that's where the wires attach.
2. Did you also buy a NF300DWH Door Speaker Update Frame? You will need this because the NDB300WH is smaller that the original door speaker and the mounting screws will not line up with the mounting box inside the wall. If you need the NF300DWH, we keep them in stock
Thanks
Chris
I own a Nutone IMA3303 and recently had a power surge which impacted the system. Everything works fine except the door chime (IA28). When the doorbell is pressed the door chime makes a strange buzzing sound. I've already replaced the chime module and the two transformers (thinking they may have been the culprit) but that did absolutely nothing. Which specific transistors receive the signal from the chime module? Could one of these be damaged even though I am not seeing any visible burns.
Thank you,
Maggie
Hi Maggie,
There aren't any transistors in the chime input circuit. There are capacitors, resistors, diodes and op-amps, but no transistors. You typically won't find burnt components when looking for problems in a modern design like the IMA3303.
It seems unusual that a power surge would have caused this type of problem. Did this happen during a storm? Is it possible that there was lightening? Lightening can travel down the push button wires and zap the Master Station, although when this happens the chime module will typically be damaged also.
It will take some investigation to find the problem, I suspect.
Chris
Thank you Chris. This did happen during a heavy lightning storm and I suspect it may have been lightning that traveled through the station. The system stopped working completely but the brought itself back up with everything functioning as normal with the exception of the door chime. The chime still responds but with a strange buzzing noise. I immediately suspected the chime module but once replaced with a brand new one the same buzzing sound comes back when doorbell is pressed.
HI Maggie,
It is very likely that the source of the problem is in the IMA3303, it could be the chime input circuit or somewhere beyond that. It's always difficult to guess at what kind of damage lightening will do.
If your interested in send the IMA3303 in for repair, please fill out an Intercom Repair Request From (the link to the Form is under the NAVIGATIOn HEADING on every page of the site) and once I receive it, I'll contact you directly about the repair of your Master Station
Thanks
Chris
Hi I just purchased a house that has the NuTone IMA 3303 the owner said it was all working just a few months ago but I am getting no error message in the LCD and I am getting a LOT of noise and crackling sounds coming out of every speaker and NO AM/FM sounds at all. I pulled the master off the wall and tested the two transformers one puts out 18.4V and the other bounces from 17.6 - 17.8 constantly (Could this be the issue) I was assuming that if both produced over 16V then they were good transformers. I also noticed that there are 4 ribbon wires connected to the terminal board and it appears that the 9 pin and 11 pin ribbon wires connect all of the interior and patio slave stations. While both (9 pin and 11 pin) ribbon wires are plugged into terminal pc board this unit produces noise and crackling sounds from speakers. If I unplug just one of the two ribbon wires (either the 9 pin or 11 pin) DOES NOT matter which one then I get a half working system meaning the radio comes back on and several room stations also play the music and the intercom works. Again doesn't matter which ribbon wire I plug in (9 pin or 11 pin) and I get the master and the associated indoor/outdoor rooms playing the radio and intercom working just fine; however, once I plug both ribbon wires to the PC Terminal board then the radio goes dead and load noise and crackling comes through all stations.
I have replaced with BRAND NEW parts the Terminal PC BOARD, The IMA 3303 Master Station and I still get the same results of load noise and crackling sounds when all the ribbon wires are plugged into Terminal PC board. I then took it a step further and removed from each room the indoor and outdoor speakers by removing the units from their cases and then removing the three wires in the back of each unit. I also removed the door bell (all wires), went back to the master station and same thing still had noise in the master station since that was the only thing hooked up now. I also went ahead and re-soldered the transformers to the low voltage wires since the original connection did not look too good. Could it be that the settings inside the master station need to be adjusted?
Any and all help would be greatly appreciated in regards to getting my system fully operational again. I just don't want to pay 2K to have everything replaced.
Any ideas how to trouble shoot further to see if there is a bad wire somewhere? Should I replace the transformers? Once I pulled everything off the walls and took off the wires I expected my master unit to work flawlessly and again I have two master units now and they both are doing the exact same thing so I do not believe this has anything to do with the master unit itself as the one I just wired up was NEW in a sealed box.
Many Many Thanks in Advance....
AL