NuTone Model IM / IMA806 Radio Intercom

New! For 1982:The IM806 was designed to pave the way into the future of radio intercom systems. In reality, it was one of the least successful models that NuTone ever produced.

The IM806 was plagued with so many problems right from the start that many dealers and installers would not sell this model. It was not uncommon in the early 1980's for manufacturers to design products that pushed the envelope of electronics and NuTone was no exception.

From a design point of view, the IM806 is the descendent of the 2561/62. Both models are decentralized designs and they can be looped-wired.

The IM806 offered some advanced features such as an optional telephone answering module and the very first built-in electronic chime module. Many of the consumer related problems revolved around the telephone answering feature and its overly complicated button sequence to operate the feature.

Also, 1982 was right about the time that stand-alone telephone answering machines and cordless phones were becoming common consumer products. The telephone interface module was not compatible with many other consumer telephone products and this would cause the module to malfunction. Sometime this malfunction would cause the home's phone line to becomes disabled and no one could call in or out of the home. How well do you think that went over?

The plastic faceplate on the IM806 master station and on the remote speakers were a slim design and the plastic was fairly thin. This caused the units to flex and become distorted when they were mounted on an irregularly shaped wall. This flexing of the faceplate would cause the controls on the faceplates to stick or not operate at all.

Then there were all of the electronic design problems with the IM806 itself. It seemed as if every few months there were more and more modifications done at the factory to solve problems. Finally, after less than 2 years, the IMA806 was released.

The IMA806 incorporated the design changes and generally was a much better model. Unfortunately it was already too late for the 806 and it slowly faded away.

The biggest problem with repairing an 806 is that it was designed on a special and individual platform. It doesn't share any parts with any other model that NuTone has ever made. This makes finding parts much more difficult and much more expensive.

PROBLEM #1: Pushbuttons

The control push buttons on the 806 master station are the cause of many problems. The 806 used a unique button design; the back of the pushbutton tabs have little magnets attached to them. The actual switch is mounted on the circuit board behind the tab. The switch is also special. It is an encapsulated reed switch. This type of switch is a thin glass tube with 2 very thin pieces of metal inside that are separated by a very small space.

When a button is pressed, the magnet on the button tab moves over to the reed switch and the magnetic field pulls the 2 thin pieces of metal together inside the glass tube and the connection is made.

As the magnets age, they loose their strength and they can't pull the reed switch closed. Also, the pushbutton assembly is mounted on little plastic posts on the back of the faceplate and these posts break off. Now when you try to push one button, they all move (which acts like you are pushing all 4 buttons at the same time) and the system will not work correctly. 

In addition, the loose buttons hang up after they are pushed (instead of returning to their "at rest" position) and that jams up the system.

To reattach the pushbuttons I have seen many different solutions. Sometimes hot glue to hold the assembly in place and more hot glue all over the top of the mounting tab (on the back of the faceplate) to reinforce it, works. I have also seen holes drilled through the faceplate with little screws and nuts bolting the assembly to the faceplate.

PROBLEM #2: Modifications & Power Supplies

Common electronic problems due to design and age. The original IM806 was plagued with problems and there are many factory modifications that could have been done at that time to solve problems. Many sets never had the modifications done.

 

There are also the failures that happen when equipment gets to be 30 years old. The power supply often needs to be rebuilt in the master station.

PROBLEM #3 Cold Solder Joints

Another problem I have seen recently are problems that arise from cold solder joints on the circuit boards used in the 806 masters. The soldering quality from 1982 is less than great and after 30 years it's not getting any better. The last 806 I had in the shop had many bad solder joints which were causing most of the problems.

All of the circuit boards used in the 806 master and all the the systems remote stations are double-sided, through-hole plated boards. This means they require special equipment to work on and repair the boards. This usually means additional time and cost.

PROBLEM #4: Tuners

The tuner on the 806 is a specially modified version of the tuner that is used on the IMA303/IMA406 systems. While it may appear that it is a digital tuner, it's not.

It is an analog tuner (mechanical) with a digital readout connected to it. This was another first in design for NuTone and I guess it was pretty cool in 1982. The modification to the standard tuner board consists of the addition of a Pre-Scaler daughter board.

The pre-scaler is the board that translates the analog signal and connects to the digital display. The problem with the tuner in an 806 has mostly to do with the basic analog tuner. As the components on these boards age, the tuners become out of alignment and work poorly.

Rebuilding a tuner is fairly simple, but realigning a tuner is an art that requires specialized equipment to do the alignment properly.

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