Beomaster 8000 (1903): A New Arrival from Illinois - First Impressions and Some Pretty Strange Modifications

I received a Beomaster 8000 (Type 1903) from a customer in Illinois for a full restoration. It arrived wrapped in some bubblewrap and polyurethane foam held together with a number of wraps of plastic foil. This bundle was then immersed in styrofoam peanuts in a box lined with 1 inch of styrofoam panels.

After fighting an hour with electrostatic peanuts crumbs and carefully cutting the many layers of cellophane wrap I had it finally on my bench:

Sadly, the heavy Beomaster had shifted around inside the sea of styrofoam peanuts and its fragile veneer corners made unhappy contact with the hard styrofoam panels and cardboard of the box as is obvious from the worn layer of foam and plastic wrap. This shows the left corner before I removed the wrapping:

And that is the corner after unwrapping:

Not super bad, but it could have been avoided by using foam panels instead of peanuts. This shows the right corner:

It survived better, but also has a little bit of damage.

Wait! What's with the strange connector a peeking out bit further back on the right side??

Here is a closer up picture:

Some kind of coaxial jack! Let's see what is inside the inclosure! I started putting the unit into 'service position'. First I removed the heat sink cover in the back:

Then I opened up the front panels, which revealed the PCBs inside:

Here a look from the top:

What a beautiful beomess!...;-)

Remarkable: The indicator light covers had the labels of the glass cover imprinted on them:

The only way I can explain such bleaching is by long lasting direct sun exposure of the unit. There is a sticker from a repair shop in Boca Raton, FL on the back of the heat sink. Maybe this unit is originally from Florida and that would explain the sun!...;-)

Even more remarkable: A wiring harness is missing in this unit that normally goes from the pre-amplifier board to four RCA jacks on the left side of the enclosure meant as an interface for connecting things (maybe an equalizer or similar) between the pre-amplifier and the output stages. Instead some wiring has been soldered directly to the jacks:

This shows the board header that normally takes the other end of the harness. In this Beomaster the pins that connected to the RCA jacks are directly connected. Two of them by a green wire and the other two just by a solder ball taking advantage from the proximity of the pins:

I understand these two connections: They simply make the connection that normally is made by wire bridges pushed into the RCA connectors from the outside of the enclosure.

Even much more remarkable: The circuit modification around the coax connector on the right side of the enclosure. A wire from the power supply and IR receiver board (PCB 6) was modified and the modification enclosed in a fat shrink tubing blob: 

I removed the blob and found a BC547B npn transistor and a small trimmer (connected between the blue wires):

The transistor appears to be wired being able to switch the connection between the remote receiver demodulator on PCB 6 and the microcontroller input pin for the remote signal. The coax connector is connected to the microcontroller input pin, i.e. makes the remote signal accessible from the outside of the enclosure.

Now the base of the transistor is connected to the swiper of the trimmer, whose track is connected between GND and pin 2 of the TDA4050 pre-amplifier that is used for amplifying the remote control signal after it comes out of the filter and first amplifier stage (inside the shield can on PCB6). Remarkably, pin 2 of this IC is basically a DC signal that is proportional to the signal strength of the received remote signal. This means that the transistor was turning on (allowing the remote signal to reach the micro controller) only when the Terminal signal exceeded a certain strength (or in other words the remote was at a certain minimum distance from the Beomaster)

So it seems that this circuit may have been used to manage the interference between two Beomaster 8000 setups in different rooms of a house that were both remote controlled. The Beolab 8000 Terminal remote control is not setup for pairing, i.e. any Terminal will work with any Beomaster 8000.

Exciting findings!...;-). Let's see what my customer decides what I should do about all these modifications.