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Beogram Commander Remote Control: Maybe This is the Final Version!..;-)

This is a follow up to my recent post about the redesigned Beogram Commander remote control board, which now works in both (DC-motor) Beogr...

Saturday, March 22, 2014

Beomaster 6000 Quad: Rebuilding the Motor Unit - Some Progress

Note: This entry is 'historic'...it turned out that the Buna-N O-rings mentioned below did not work out. Please, use rings made from EPDM. I used model E70032 from the O-Ring Store (theoringstore.com). The Buna N rings cracked after only one month, and I had to replace them with the EPDM rings. Check out the update on this repair procedure and a detailed repair video at: http://beolover.blogspot.com/2014/05/beomaster-6000-4-channel-rebuilding.html

I received the belts for the motor unit of my Beomaster 6000 Quad from McMaster. They are 'metric Buna-N O-ring, 2mm width, 50mm ID' (9262K208). I measured the broken belts as good as I could, and it seemed these dimensions would fit the bill. The original belts had only 1.8 mm diameter, but 2 mm is all they had.
So I set out to put them in. Not a task for the faint of heart. It is immediately evident that the indicator tapes need to be removed. Sweat started building at the thought. But there is only one way now with this Beomaster: forward!
The critical moment is when one takes the V-shaped retaining clips out that clamp the tapes to the purple wheels. Per service manual one is to push them out laterally, which works fairly well (three of them had sort of bonded with the tape/wheel, and it took a bit of force until they started moving). It is best to move the grooves in the wheels a bit away from the display element to obtain a clear path for the clips for moving them out. Here is a pic:

After I removed the five tapes, I went on to get the shaft out. All one has to do there is to remove the plastic bearing at the end of the motor unit and wiggle it out (see below a photo where I put it back in - that should clarify the process). It is a good idea to put a box into the cavity of the motor unit, to lift it out a bit, to create a better working situation.
Here is the shaft after I had it out...a pretty interesting design. The clutches are just metal pieces that are pulled into place by coils (OL1,2,3,5,6 in the schematic).

Then I loosened the potentiometer nuts. Of course my Beomaster 6000 Quad did not come with the appropriate Band and Olufsen supplied special ~1mm thick 10mm wrench. But I am a man of the Dremel, and so I had the 'collet wrench' that came with the set. This wrench has the perfect thickness, but is slightly to small (it may be a 9/32 - not sure). I used the Dremel itself with a grinding tool to widen it up a bit to a 10mm opening:

This fit perfectly:

Note: this pic was taken after the job was done.

All one has to now is to loosen the nuts and wiggle the pot is out. I forgot to take a pic when they were out - the heat of battle...I then put the belts on their groves on the purple wheels. They just stayed snugly put in them by their own tension. Then I put the pots back in and tightened the nuts.

Now came the second hard part: To get the shaft back in while pulling the o-rings into position. I did this in a 'caterpillar' like motion, moving the shaft a bit pulling the o-rings one ager the other on it while moving it a few millimeters forward, moving the rings and so forth. Here is a when I was about halfway through:

And here after putting it all the way through:

After installing the shaft all the way, I tried to turn the wheels by turning the pulleys on the shaft, and everything felt pretty solid and in good contact, while having enough friction to reliably turn the wheels. It seems the belts may do the job.

Now I needed to replace the motor coupling, which was completely rotted away. Here is is before:

And with the new piece of a 3mm ID poly tubing piece:

Since the shaft can only be stuck into the coupling when the motor is installed, I needed to pull the shaft again a bit back, install the motor back into position, and then press the shaft into the coupling. This worked very well:

So far so good. The next step is to put the bands back in. This is probably the biggest problem since the retaining clips have degraded and lost their elasticity. I tried to bend one a bit together to be able to get it into the wheel in a 'dry run' without a tape (not sure what I would do if I damaged them...)
Anyway, this is what happened, as you may guess:

It immediately broke after applying very little force. I guess the others will not be much different. So a solution needs to be found. I have a few ideas, but this needs to 'percolate' a bit more...aside from this damage, a few wires came off of board 12 (motor control) since the board chafed quite a bit on the cardboard box while I was fighting with the shaft and the o-rings. But this is a minor problem. I thought that would happen and I took some nice pics before...Enough for today. More later.

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