NuTone IM3303 Master Station - Common Failure Mode #1 - No Volume
Monday, February 2, 2015 at 8:12AM "Everything Seems Like it should Work - There Just Isn't any Sound"
This simply sums up the comments and reports we get from homeowners about their NuTone IM3303 and IMA3303's Intercom systems.
In most of these cases, the Master Station appears as if it wants to work, however there's simply no sound. As bad as this may seem, the positive side of this situation is the display is lit up and it shows not only the time but the radio station readout as well.
Since the Display is located on the same circuit board as the Micro-Controller, and the Micro-controller is solely responsible to driving the clock, it is a fairly safe assumption that the Micro-Controller is not the source of the problem with these sets.
The damage to this IM3303 was extensive and it seems obvious that the Master Station had been failing for a long period of time.
You can see the damage to these two resistors. The darkened area under the circuit board didn't happen overnight; it's a long process to darken a board to this extent. The two transistors to the right of the resistors had also failed.
More crispy resistors
Here you can see how the top of this capacitor has "tented' up to relieve the buildup internal pressure.
The pressure was great enough to lift the capacitor off the board and crack the sealant around the base.
In this close-up view, you can see how burnt the small resistors are. The larger resistors are wire-wound and rated at 2 watts. They had become so hot that the ceramic/epoxy coating has begun to crack and fall off the body of the resistor.
In the end, there is a substantial number of components that were replaced to bring this IM3303 back to life.
Here's a video showing the condition of this NuTone IM3303 as we received it, and its final testing after the repair had been completed:
To find out about having your IM3303 or IMA3303 Repaired: Pleae fill out an Intercom Repair Request Form