A Guaranteed Way to Ruin a IM3003 Master Station

Contrary to what many people think, better is not always good.  This IM3003 was modified by a previous owner in an attempt to improve the quality of the sound from the master station.

The original NuTone speaker cone was replaced with a somewhat larger size speaker cone from Radio Shack.  There are many problems with this idea, but the biggest problem is that NuTone uses speakers in the IM3003 which are rated at 25 ohms.  The Radio Shack speaker cone was rated at 8 ohms.

The little amplifier IC in the IM3003 cannot supply enough current to drive a 8 ohm speaker.  The 8 ohm speaker will overload the amplifier, causing it to run burning hot and quickly fail.  This is exactly what happen to this IM3003.  Upon initial testing the amplifier heat sink became smoking hot after the set was powered on for about 1 minute..

A normal repair for a IM3003 of this age is to rebuild the power supply and clean the controls. This IM3003 also required having the amplifier IC and voltage regulator replaced.

The overall sound quality of any Intercom system has more to do with the design of the amplifier than it does the speakers it drives.  Buying the highest quality Bose speakers and connecting them to your NuTone intercom system will not make it sound like a Bose system, it will just ruin your intercom system