Beogram 4000 – servo optical diaphragm adjustment

[PeteV]

Hello,

As part of my BG4000 restoration, I am looking at the tonearm tracking adjustment. On page 4-6 of the service manual, it states the following:

The first part to adjust the forward direction is clear. However, point 6 makes no sense for backward adjustment – what is meant by 10cm? Certainly not the arm. Even 10mm would be a massive amount. I am wondering if they mean 10 turns backwards?

In the service note, issue no. BG1, they state that adjustment of servo sensitivity is for 15-19 record groves. This is different from the sensitivity of 4-6 grooves of the main manual in the forward direction, and does not really relate to the 10cm mentioned for backward adjustment.

My second question relates to the same service note BG1, see below:

The addition of the preset pot as shown makes no sense as shown. To match the circuit on the left, it seems to me the track shown by my red arrow would need to be cut.

Any advice gratefully received.

[PeteV]

Hmm, my images are not being shown. Let me try using attachments.

 

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[hcraig244]

Take a look at this……

Beogram 4000: Tracking Sensor Bulb Replacement with LED

[PeteV]

Thanks. I have been looking at his site extensively, a goldmine of information, but I had not watched this video which answers all my questions!

[hcraig244]

It doesn’t address your question around item no 6 on the above procedure, which I cant either…..I note that Rudi deftly avoids that  final step also ;¬)

Craig

[PeteV]

Yes, that is true.

But when he does show the arm tracking backwards (almost as a aside), it shows a massive deviation before it starts moving, which mine does as well, maybe as much as 10mm? It is way too much deviation to copensate for slightly eccentric records (of which there are many 🙄). I think the time constant on the whole system is too slow to compensate for record eccentricity anyway, so the whole reverse direction function is pretty pointless, presumably why it was removed from later models.

Anyway, I’m not going to worry about that anymore.

Thanks for your help 👃

Peter

[Author]

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