Dual 503-1 speed ?

I have a Dual 503-1 turntable ,from a thrift store ,with no manual. There seems to be no way of adjusting the speed, and it ran at about 33.8 with the first belt. I got a thicker new belt (.025 thickness)that makes it run at 32.7. Would this be the only way to adjust speed,by varying belt thickness? Manuals seem to be non- existant.Did Dual make this turntable($350, 1991) with no speed adjustment?

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Originally Posted by Bill K Davis

Did Dual make this turntable($350, 1991) with no speed adjustment?

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It appears as though they did.

Here is a link that includes an original brochure.

http://dual-reference.com/tables/CS503-1.htm

In theory, the thickness of the belt shouldn't make a diffference. The key is the relative diameters of the two elements around which it's wrapped...like bicycle gears.

audionoob and the rest thanks. I'm going to put some duct tape around one of the spindles the belt goes around. Unless someone has a better idea.

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Originally Posted by 02audionoob

In theory, the thickness of the belt shouldn't make a diffference. The key is the relative diameters of the two elements around which it's wrapped...like bicycle gears.

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But Bill's experiments thus far show otherwise - he's got one too fast and one too slow. I say either just go with the fast one ("better sharp than off pitch") or look for a third belt solution somewhere between the two you've already tried. Tape is going to make the pulley unround and that's not going to sound very good.

I have the Dual CS-5000, which was Dual's TOTL model, and it too has no speed adjustment. When I replaced the belt, it ran noticeably fast, but then I saw why: there are two ridges on the inside of the turntable platter onto which the belt fits, and if the belt isn't on the lower of the two ridges, the table runs fast. I have no idea if that's the same setup as yours, but it may be, and might be worth looking into. 'Hope this was useful.

I guess I should try another belt. I think the original was .0189, the next.025 and there is one available .0204. It should be close at least. :arf:

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Originally Posted by Kevio

But Bill's experiments thus far show otherwise -.

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But the point is, there's most likely another reason besides thickness, such as traction/slippage, tension/strain or the situation emaidel described. If you think about how the belt works, I don't see how you could determine that the thickness itself is the difference.

I assume the effect we're seeing is because a belt, unlike a bicycle chain, stretches. But, yeah, checking for slippage would be a good idea here. If the table is running slowly because of slippage, there's probably going to be some wow and it probably is going to start up slowly.

A poster at Vinyl Engine has the answer,with photos. We are saved. Look in the Dual forums,by avr.:2:

There's an undocumented speed adjust control - http://www.vinylengine.com/phpBB2/viewtopic.php?t=6122

On a slightly different topic...How does one go about accurately timing the rotation?

The best way is with a strobe disk.

I've also put a mark a small mark on the edge of the platter, and counted the turns. In 3 minutes, it should turn exactly 100 times at 33 1/3 rpm. Using a stop watch works well for this.