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I finally had some time to continue the LED-ification project of my Beomaster 6000 4-Channel (several of the lightbulb fixtures had broken out tab-receptacles, and I did not want to use tape to fix them in place, so I decided to do it with LEDs)
I made some major progress on this today, and it seems everything is finally working. More about that after I do some more testing of this set-up.
I was confident enough to re-install (for the 4th time, I think...patience is a great asset with the Beomaster 6000...;-)) the indicator bands of the motor unit. I realized that I previously adjusted them slightly wrong in their position. So I wanted to share here how to do it right:
The small white dots in the indicator panel are meant to adjust the bands relative to the potentiometer position. This is how I aligned them this time before pushing in the clips (see here for details on the entire procedure and a video):
Oh well, another setback!!... While messing with the output amplifier and doing the tuner dial string etc...I had to witness the degradation of the Buna N O-rings that I installed a month back into the Beomaster 6000's motor unit. I could literally see how cracks in the Buna N rings developed that increased in depth every day in a noticeable way. I think in another month the rings would have broken and fallen off by themselves. Here is a picture of the damage:
Pretty uncool! Anyway, this meant I needed to redo everything, and I already had the indicator bands installed.
I studied up on O-rings and the materials they are made from. It turns out that the best material for 'drive belt' uses under tension is EPDM rubber (ethylene propylene diene monomer rubber). I found the "Parker O-ring Handbook", and guess what, it has a chapter on "Drive Belt Applications" (section 3.17). There it suggests material "E0751-65" as ideal for drive belt applications. A bit of internet sleuthing then yielded that this is EPDM...unfortunately it is very difficult to buy Parker products as a private person...it seems they have a distribution system that is loth of modern purchasing methods, i.e they want you to go to a local handyman location to pick up the O-ring...crazy! So I went to the O-ring store, and ordered six of their E70032 model, which is a 1-7/8 inner diameter 1/8" thick ring made from EPDM. I also went through a learning curve with regard to the inner diameter - the original rings measured 2" diameter, and I installed the E70033 model first, which has 2" diameter, only to learn that two of the potentiometer drives slipped with these due to a bit higher resistance in these pots...so I had to do it a 3rd time with the 32 size...live and learn!
Anyway, I was able to finally complete the repair, and I made another video about the process. This video shows the entire process: Removing the indicator bands, putting in the new rings, and putting the bands back in. There is also a demo of the rebuilt unit in action at the end. You can find it on YouTube:
********Please, note that the video does not make clear how to properly position the indicator bands relative to the potentiometers. See this post for details.**************************************
Another interesting issue about this repair procedure was the brittleness of the V-shaped plastic clips that hold the indicator bands to the purple drive pulleys on the potentiometers. The original clips immediately broke when I tried to squeeze them a bit when reinstalling the bands:
So I took measurements of one of the still intact ones, and made a model in Autodesk Inventor. Then I exported the finished model as an STL file and printed it on a Makerbot II in yellow PLA (I thought the yellow would work well with the purple drive wheels, adding to the colorful interior of the Beomaster 6000....;-).
Here are the new clips:
Pretty cool! But I had to manually Dremel the grates off at the side that connected to the plate of the printer to prevent damage to the indicator bands when sliding the clips in.
This worked very well. They can be installed by squeezing them together with needle nose pliers and pushing them in from the top while bunching the band ends together into the 'crack' (sounds more complicated than it is - watch the video posted above - it shows this process in detail).
In a second step, the clips are pushed into the wheels until they seat against the wall:
And that is pretty much it. I really like the yellow-on-purple theme...;-). Watch the video for a demonstration of the rebuilt unit and the clutch mechanism.
