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 Post subject: Re: Questions Regarding Expert Senior Motor - Tracking
PostPosted: Tue Dec 24, 2013 6:12 pm 
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Victor III
Joined: Wed Jan 07, 2009 11:07 pm
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Graham,

Please see the attached photos.

First, does this demonstrate proper use of the Wilson alignment protractor, with the soundbox face parallel to the lines on the pointer? If so, then the angle of alignment is consistently off somewhere between 3-8 degrees. Judging from the literature you shared, that doesn't seem to be too much?

Image

Second, please see the photos showing the crank escutcheon and the tone arm spindle. Which distances do I need to measure? As always, your help is invaluable!

Image
Image


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 Post subject: Re: Questions Regarding Expert Senior Motor - Tracking
PostPosted: Tue Dec 24, 2013 6:35 pm 
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Victor III
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Garret wrote:
First, does this demonstrate proper use of the Wilson alignment protractor, with the soundbox face parallel to the lines on the pointer?


No, the needle point should be touching the pointer on the other side of it, i.e. within the cutout section. ;)


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 Post subject: Re: Questions Regarding Expert Senior Motor - Tracking
PostPosted: Sat Dec 28, 2013 12:43 pm 
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Victor II
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You may find it easier to use the EMG 2 spring soundbox for this exercise. This model has no stylus guard which can confuse sightings. You are, in theory, looking to view the plane of the diaphragm immediately above the needle but, for all practical purposes, reading from the front face of the soundbox is accurate enough. It can also be an advantage to draw arrows on the parallel protractor cursor lines---perhaps in different colours---so as to make it easier to establish the correct line when viewing either side of the soundbox etc.

Please also note that the Wilson protractor drawings you have downloaded do not print out accurately ie. the inch measurements do not measure exact inches when on paper. This is of little consequence per se in terms of checking accurate tracking since the vital measurement is distance AY (half the diameter of the motor spindle---half of 0.284 inches = 0.142 inches or 3.61 mm) but it is as well to keep everything correct if possible---for comparative purposes, if nothing else. I suggest you draw the main part of the protractor on a new sheet of paper and dimension accurately. The cursor as downloaded will be fine but ensure that it is pivoted exactly on the vertical read-out zero line and on the centre line of the cursor.

It is also worth noting that readings can be taken with the needle at any point along the horizontal YZ axis but Zero is usually convenient if tracking is not too far out. The needle is positioned within the cut-out portion of the cursor pointer and not on the outside---see photos 4 and 5 showing zero tracking error.

As recommended previously, the whole operation becomes much easier if the case lid stay is removed, enabling the lid to be moved out of the way.


To check tracking proceed as follows:

1. Read previous posts in this thread carefully and then determine “offset” as shown previously on page 6 of “The book of the fibre needle”. The Expert tonearm should confirm a design figure of 3.75 inches. Photo numbers 6 & 7.

2. Check motor spindle centre to tonearm bearing centre equals 11 ½ inches. Photos 8, 9, 10.

3. Refer to second “overlap” table as previously shown on page 9 of “The book of the fibre needle”, ie that which refers to “Actual tone arm length from centre of back-pivot to needle point”. The 11 ½ inch measurement shows an overlap of 0.54 inches at an “offset” of 3.75 inches.

4. Ensure the soundbox is positioned on the tonearm so that the face of the clamp ring is coincident with the inner edge of the larger diameter on the end of the tonearm and that the plane of the soundbox is at ninety degrees to the turntable. Then twist the soundbox on its axis to set 0.54 inch “overlap” measured from the motor spindle centre using a needle projection of ½ inch from the chuck face---photo numbers 3 & 11. Photos 1, 2, 3 show the overlap measured on a specially machined rule to accommodate half the motor spindle diameter but, although logical, this is not absolutely essential.

5. Place the protractor on a 12 inch record and measure tracking error at various points across the disc. The plane YY depicts the diaphragm/needle orientation, the extension of which is visually used to match the parallel lines shown on the protractor. Photo numbers 12, 13, 14, 15, 16 show the error readings at 6, 5, 4, 3, 2 inches from the spindle centre. The photos are taken from measurements on my Expert Senior and it will be seen that the maximum divergence from zero error is 2 degrees (negative in this case). A zero reading confirms a perfect tangent to the annular recorded ring where the needle is resting and variance of two degrees either side ie positive or negative is quite acceptable in terms of potential record wear. Typically, results will only show two perfect tangent positions during the traversing of the record with all other locations showing minor (acceptable) errors---if tracking is correct.

6. I have used the BJ protractor to demonstrate the system as the important aspects show up quite clearly on the photographs but the principles enshrined in the Wilson protractor are identical. It is very important to view from directly above the soundbox to ensure complete accuracy.

7. It is worth noting that all gramophones should be set up in this way but “offsets” may vary greatly. This is of little consequence so long as careful notice is taken of the actual measurements and reference is made to the appropriate charts.


Attachments:
File comment: Photo number 10.
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File comment: Photo number 5. Error is, in fact, zero but curled paper is misleading viewed from the side !
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Last edited by emgcr on Sat Dec 28, 2013 1:24 pm, edited 1 time in total.
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 Post subject: Re: Questions Regarding Expert Senior Motor - Tracking
PostPosted: Sat Dec 28, 2013 12:49 pm 
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Victor II
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Continued..............


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 Post subject: Re: Questions Regarding Expert Senior Motor - Tracking
PostPosted: Sat Dec 28, 2013 5:12 pm 
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Victor III
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Location: near Utopia, UK
Profuse apologies both - I have muddied the waters here. Both my brief instruction in a recent post, and those included with the printable Wilson Protractor, were incorrect. I should have left it to the master! Here is a revised version and the brief instructions should now be right. I've removed the original from my original post.

As Graham says, it may not necessarily print to scale, depending on your printer, but it's possible to drag and re-size the images (both must be altered identically) if you want it printed exactly in inches.


Attachments:
Wilson protractor print 2.docx [187.39 KiB]
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 Post subject: Re: Questions Regarding Expert Senior Motor - Tracking
PostPosted: Sat Dec 28, 2013 6:35 pm 
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Victor II
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Posts: 494
Location: Hampshire, England.
Many thanks Andy---most helpful to all.

I too have made a couple of small errors (it is 12 years since I studied this subject in detail !):

1. With reference to the table on page 9 of the EMG booklet in the previous part of this thread, I used the 0.54 inch overlap figure which is based on a total tonearm length of 11 ½ inches but, of course, I failed to add the overlap amount to reach the overall length between tonearm centre and needle point = approximately 12 inches. The correct overlap figure should be nearer 0.50 inches which is also confirmed by the table on page 8. In practical terms such a small variance (40 thou') will make very little difference to the tracking reading but it is best to be as accurate as possible ! There is one benefit, however, which is that by measuring in this way, variations of turntable height are automatically catered for which could be significant in the case under review.

2. I have quoted a reading at 6 inches from the turntable spindle but this should be 5 ¾ inches as at greater distances than this the needle falls off the edge of the record !

3. Point 2---measurement of motor spindle centre to tonearm bearing centre---(photos 8, 9, 10) could be slightly inaccurate since the end of the ruler is unable to measure to the exact centre of the tonearm although it is possible to gauge roughly by eye. Increased accuracy is given by measuring to the external diameter of the tonearm or tonearm bearing casing and then adding on the relevant radius. However, in the case of EMG tracking, I have had cause to make a dummy tonearm bearing spigot which, together with an 11 inch spacer, produces a completely accurate setting---see photo below.


Attachments:
File comment: Setting accurate tracking on an EMG---11 inches from motor spindle centre to tonearm bearing centre.
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 Post subject: Re: Questions Regarding Expert Senior Motor - Tracking
PostPosted: Sun Dec 29, 2013 8:42 am 
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Victor II
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Location: Hampshire, England.
The attached schedule---with conclusions---shows all of the important tracking features and variations of my own Expert Senior (offset 3.75 inches) which I hope may be of general interest/assistance. Calculations for Experts Junior and Minor are similar---they have identical tonearms.

The really important point to remember is that when playing any gramophone which has the facility of being able to vary the soundbox/overlap angle (ie no fixed, or pre-set, bayonet etc), the fundamental requirement is to become visually familiar with what the necessary overlap (confirmed from the tables for your own machine) looks like---in this case 0.510 inches. Set this overlap---from the spindle centre---(either by needle extension and/or soundbox twist) every time a record is played and tracking will be, for all practical purposes, spot on. Confirm your initial results with a protractor, after which, no further basic change should ever be necessary. It all sounds complicated but soon becomes second nature when the correct setting is readily recognised.


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EXPERT SENIOR TRACKING.pdf [185.48 KiB]
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 Post subject: Re: Questions Regarding Expert Senior Motor - Tracking
PostPosted: Tue Dec 31, 2013 10:25 am 
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Victor III
Joined: Wed Jan 07, 2009 11:07 pm
Posts: 895
Graham,

Wow! Thank you for posting. I am away for the holidays, but will look into these details further upon my return.

Many thanks!

Garret


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 Post subject: Re: Questions Regarding Expert Senior Motor - Tracking
PostPosted: Tue Jan 21, 2014 12:51 pm 
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Victor III
Joined: Wed Jan 07, 2009 11:07 pm
Posts: 895
Graham,

Measuring from the center of the turntable spindle to the point of the needle when the soundbox is turned to a roughly optimal angle for playing, the overlap is .861". So clearly, we might have an issue here. You will notice in the image that the soundbox is resting on the turntable spindle, but even when adjusted, the overlap is still a significance variance from the optimal reading suggested early of approximately .50". What do you think? I hope this explanation makes sense!

Image


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 Post subject: Re: Questions Regarding Expert Senior Motor - Tracking
PostPosted: Tue Jan 21, 2014 2:35 pm 
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Victor II
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Posts: 494
Location: Hampshire, England.
Garret, I think you are starting somewhat back to front ! There is not a fixed or optimal soundbox angle as such---rather, after having established the motor spindle/tonearm axis distance between centres and then added the overlap, the soundbox angle will automatically end up in a certain ball-park area. This will then roughly correspond to the angle recommended by the manufacturer if the tracking is correct.

It is important to proceed in definite steps:

1. Confirm that the offset is 3.75 inches. So long as the soundbox is correctly mounted on the tonearm all should be well since it is very difficult to bend a tonearm ! Please check it however. This is very quickly done with a straight edge, set square and ruler.

2. Determine the precise distance from the centre of the motor spindle to the axis of the tonearm. To do this, first measure the distance from the motor spindle centre to an external point on the tonearm bearing casing (probably the top rim of the clamp ring) but be careful to ensure that your ruler is parallel to the deck-board or accuracy will be compromised. Call this distance X. Next, use your vernier calipers to measure the external diameter of the tonearm bearing clamp ring at that same point. Then divide by two to give the radius---call it R--- which can then be added to the initial length X to give the total distance between centres. Call this XR.
It is vital to know this exact distance.

3. Refer to the left hand chart of the "Table of best overlaps". Let us say that XR is 11.5 inches, then the overlap will be 0.5 inches. In other words the needle point will be in front of the motor spindle centre by half an inch. The fact that this is correct is confirmed by the right hand chart which allows for the total distance from the tonearm bearing centre to the needle point. Call this XRN. You will see that the figure is quoted as 0.51 inches at a total XRN distance of 12 inches---nearly identical for all practical purposes.

4. Use the protractor you have made to take a series of readings at different points across a twelve inch record which will visually show how the tracking error varies (often negative and positive---zero shows a perfect tangent ie perfect tracking) as the needle traverses the disc. Perhaps do this with two different needle projection lengths---say 3/8th inch and ½ inch---to confirm and demonstrate optimal settings.

Let me know what your actual measurements are and we can then begin to establish whether or not your motor is in the correct position.


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