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Beogram 4002 Opto-tracking adjustment

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Krolroger
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Krolroger posted on Mon, May 1 2017 1:09 PM

Hello All,

I'm fixing up a BG4002 (type 5514) and trying to adjust the tracking mechanism.

The available adjustment seems to be a little bit crude, frankly, to the extent that once you think you've got somewhere, when you tighten up the set screw, it goes off again.

I note that Rudy with his very tidy LED alternative adds a trimming pot to adjust the light source for fine tuning after you have got the basic adjustment.

My question is would this sort of set up work with the standard 24v 40mA (?) incandescent bulb?  Say a 250 ohm 500mW single turn trimmer?

Or would this introduce unintended consequences?

Regards,

 

 

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Krolroger
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One more question, if I may.

There is quite a lot of slop in the platter spindle bearing so should one take the 23mm detector arm measurement as if the platter is under slight tension from the drive belt?

Regards,

Krolroger

sonavor
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I don't take that measurement with any belt tension on the platter. Because the spindle has three adjustment screws for its horizontal position I move the arm over the platter and take three measurments - One nearest the outer edge, one near the spindle center and one towards the back of the platter.  When all three points have 23mm then you know you have a perfectly level platter. It usually takes me several iterations of adjustment and measuring to get it set right. It is also another one of those adjustments that you need to make sure your starting point isn't already near the limit of one of the adjustment screws.

Regards,
sonavor

Krolroger
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I'm guessing that the set screws for the rails are as the factory set them - quite a variation from one end to the other relative to the base of the floating chassis - so my instinct is to leave them alone.  I don't think the deck has suffered any massive trauma other than misadjustment and years of neglect so I am assuming the rail adjustment is ok.

My latest challenge is to reproduce the 5 cabinet guiding washers, the awful clear plastic ones having disintegrated. Currently making a silicone mould, with a view to making a resin casting or maybe using a low temperature alloy instead as these washers are nearly always missing or unobtainable. Luckily I had a spare set to make a mould from.

Has anyone had a go at this - other than 3d printing?  Here's a picture of another use for a hummus pot.

Regards,

Krolroger

 


sonavor
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I believe Søren Mexico made some out of aluminum a while back.

Regards,
sonavor

Søren Mexico
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made these and it worked out good, no need to adjust the trim on mine, but maybe other decks may need adjustable eccentrics, the original  square ones gives 4 positions as the center hole is off center

Collecting Vintage B&O is not a hobby, its a lifestyle.

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