Dual 505 Protractor Arc ?

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PeD
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Dual 505 Protractor Arc ?

Post by PeD » 18 Aug 2013 17:26

I've asked a question re-overhang of a cartridge on the "Dual" part of the forum but with no luck with an answer yet. (could be I've worded the question incorrectly) so I thought I'd try again here.

After renewing the stylus on an Ortofon FF15e Mk11 cart. I used the "arc protractor" as supplied by Dual in their manual for the CS505.

I've found that the stylus is not reaching the marks on the arc of the protractor. The Dual head shell has been fitted with an 1/2" adaptor.

As all Duals seem to have been fitted originally with a Dual/Ortofon OM type Cart. could this be why the measurement is out with a FF15e cart. Does the OM cartridge have a bigger overhang it looks a longer bodied cartridge than the FF15 ?

Would fitting an OM 5 or 10e solve the problem or do I need to use a different protractor and would the tracking be correct for the ULM arm ?

Regards

Peter

lini
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Re: Dual 505 Protractor Arc ?

Post by lini » 18 Aug 2013 20:52

Peter: Did you already check with a ruler, whether the protractor has actually been printed to scale?

Greetings from Munich!

Manfred / lini

PeD
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Re: Dual 505 Protractor Arc ?

Post by PeD » 18 Aug 2013 21:32

Thankyou for the reply. The protractor arc is as the original at 221mm.

But, there's always a but the protractor is from the CS505-2 and my deck is a CS505-1. Acccording to both the 505-1 and the 505-2 manuals the effective tonearm length of each deck is 221mm.

I assume from this that in theory the 505-2 protractor would be correct ?
The only thing I can see that changes on the decks is how the headshell fits to the tonearm.
The stylus would appear to be 5mm short of the "arc" on the protractor.

Regards

Peter

lini
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Re: Dual 505 Protractor Arc ?

Post by lini » 19 Aug 2013 08:35

Peter: Hmmm, strange... 5 mm too short would seems like a lot, 'cause most cartridges have a horizontal distance of roundabout 10 mm from the needle tip to the (middle of) the mounting holes (which also goes for the OMs, btw - and I don't think an FF15EII would differ much from that...).

Could you post a pic, maybe? Perhaps I could spot something then, but right now I haven't really got a good idea, what might be the reason...

Greetings from Munich!

Manfred / lini

PeD
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Re: Dual 505 Protractor Arc ?

Post by PeD » 21 Aug 2013 12:14

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At last managed to upload photos of the Dual arc.
Hope this is of some use. I'm not sure if the angle of the line to the arc is significant but I cannot get the tone arm on the Dual to line up with it.

Regards

Peter

JaS
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Re: Dual 505 Protractor Arc ?

Post by JaS » 21 Aug 2013 14:36

Hi,
Where does the tonearm end of the protractor fit :-k

Regards,
JaS

PeD
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Re: Dual 505 Protractor Arc ?

Post by PeD » 21 Aug 2013 18:59

JaS wrote:Hi,
Where does the tonearm end of the protractor fit :-k

Regards,
JaS
The end of the Dual protractor has a semi-circular cut out that is
supposed to fit against the tone arm vertical circular mount, called "the bearing frame" in the service manual.

I'm begining to wonder if in fact this protractor arc is correct.

Regards

Peter

lini
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Re: Dual 505 Protractor Arc ?

Post by lini » 24 Aug 2013 01:30

Peter: Just to give you an interims reply, I'm still puzzled. But did you measure the tip to mounting hole distance in the meantime?

Greetings from Munich!

Manfred / lini

PeD
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Re: Dual 505 Protractor Arc ?

Post by PeD » 24 Aug 2013 12:03

My best measurement is 9mm from the tip to leading edge of the mounting slot bolt holes. This is as far forward as the cartridge can go.

Hope that makes sense ?

Peter

lini
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Re: Dual 505 Protractor Arc ?

Post by lini » 25 Aug 2013 08:37

Peter: Yup - then that's within the usual range, as already assumed above. Hmmm... I'm really out of ideas at the moment. But, well, then you can always use a regular Baerwald/Loefgren A two-point protractor instead - preferably one for DIN radii, so that the null points are at 63.1 and 119.3 mm.

Greetings from Munich!

Manfred / lini

bloode
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Re: Dual 505 Protractor Arc ?

Post by bloode » 15 Mar 2019 19:52

I'm now trying to fit my new Ortofon Super OM 20 in accordance with the same protractor on the 505-2. I am having the same problem as the OP. I, too, question the accuracy of this supplied printed/printable protractor as the sound from the stylus is absolutely beautiful throughout the record playback. I've listened to open playback on my system, and more closely with headphones to a few needledrops I did yesterday. All sound great. I would think that the sound itself is more proof than the printout. As far as protractors, I'm still not clear on which protractor would be best as I didn't immediately find a 221m overhang option in the protractor section. But I will try to track down this Baerwalk/Loefgren A mentioned by lini above.

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Re: Dual 505 Protractor Arc ?

Post by DSJR » 16 Mar 2019 17:13

PLEASE!! using a card protractor, set the inner null point at a nominal 60mm from disc centre.

Lini, I checked several times this last year using an assortment of alignment protractors to ensure I wasn't giving the wrong advice here. The plastic Dual overhang gauges I have here set the stylus to a 58mm inner null point on a card type protractor and this is close enough to 60mm so as not to matter with a typical elliptical stylus in my experience. Dual do the rest as regards offset angle and so on, so no need to worry.

The Ortofon OM20 stylus (the 'Super' bit is in the cartridge body, not the stylus assembly) is a straightforward 1.5g tracking elliptical with NO special needs and as each record you play has a different inner groove distance from disc centre, I'd seriously suggest not to worry unduly here, as it's really not a problem.

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