AR77XB out platter balanced?

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kiwidad
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AR77XB out platter balanced?

Post by kiwidad » 17 Jan 2020 16:51

I picked up an dar77XB in excellent condition before Fedex got a hold of it and its now more of a project. However something I notice on the outer platter is what looks like a small piece of metal glued on the outer part of the inside. I had never read these were balance like that by AR.Has anyone else spotted this or has the table been monkeyed with by someone previously?

lenjack
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Re: AR77XB out platter balanced?

Post by lenjack » 17 Jan 2020 18:17

It certainly seems that a user did this. AR was too meticulous to have allowed an unbalanced platter to have left the factory. Maybe you could find out from previous user(s).

derspankster
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Re: AR77XB out platter balanced?

Post by derspankster » 17 Jan 2020 19:29

No, both my XA's platters are balanced like that. It's factory - don't remove it.

der

lenjack
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Re: AR77XB out platter balanced?

Post by lenjack » 18 Jan 2020 02:03

Mine wasn't. I learn something new every day. :o

derspankster
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Re: AR77XB out platter balanced?

Post by derspankster » 18 Jan 2020 15:59

lenjack wrote:
18 Jan 2020 02:03
Mine wasn't. I learn something new every day. :o
I do too lenjack.

der

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Re: AR77XB out platter balanced?

Post by pivot » 26 Jan 2020 01:55

My XA platter was sent to George Merrill back when he was involved with (owned?) "Under Ground Sound" - lo many years ago. George coated the platter top with lead and balanced the platter buy bonding/gluing on a lead strip very much like what you describe.

I believe the platter had a lead balancing "patch" on it before it went to George but we are talking DECADES ago and my memory may not be perfect.

My suspicion is the piece of metal on the platter is indeed a weight to balance the platter and may well be factory original. I would leave it alone.

gkimeng
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Re: AR77XB out platter balanced?

Post by gkimeng » 26 Jan 2020 18:51

AR platters were theoretically machined for balance. But in the real world, a small weight here or there makes the difference between a part moving on down the line or being QA rejected.

lenjack
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Re: AR77XB out platter balanced?

Post by lenjack » 26 Jan 2020 19:35

Interesting. Why haven't we seen this from other makers? AR was so meticulous. As I mentioned near the top of this post. mine didn't have an extra weight, and I'm surprised that even with 1960's technology, that this was needed.

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Re: AR77XB out platter balanced?

Post by gkimeng » 26 Jan 2020 20:48

Of all the turntables I ever had from that era, the AR's platter spun the longest without power. So my guess is that their tolerances for balance were way tighter than most other consumer turntables.

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Re: AR77XB out platter balanced?

Post by lenjack » 26 Jan 2020 21:21

Another tribute to AR.

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