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Old 7th December 2010, 12:41 PM   #151
kevinkr is offline kevinkr  United States
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Quote:
Originally Posted by GTHICM View Post
So Kevin, now that you have experience with 3 motors, is is safe to assume that the bearings generally wear to the point that replacement ought to be considered critical? I wil probably do so myself when mine is apart, but of course would not like to do so if they are not worn much.

Any conclusion on the best option for motor suspension bushings?

Actually I don't think the evidence is there to say that the motor bearings are generally worn enough for it to be mandatory to replace them, rather I am playing it safe. Purchasing the punches and other odds and ends required to make the felts for a motor here or there is not that convenient. The kits from Analog Depot, JEC965 and elsewhere just make it the most convenient and logical option. Time was also an issue, cleaning and re-oiling the bearings would add several hours to the process and we had an afternoon literally to rebuild these two motors. The other issue for me is that I don't have the gauges required to determine the condition of the original bearings so rather than do all of this work only to find the bearings are severely worn I just replace.

I would recommend purchasing the bushings from Schopper and staying close to the original design conception although I am satisfied that the noise issues in my MKII don't relate to the choice of Geltec bushings, but to a design change that makes it much more sensitive to belt tension/condition than a MKI. (Only other MKII I am familiar with behaves the same way.)
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Old 8th December 2010, 05:56 PM   #152
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MKI Observations:
Something I forgot to mention that I noticed on the two tables I worked on, both of which were made in 1959 is that the idler pulleys are stamped on the bottom with a production date - at least through 12xxx serial number machines. it is not clear to me whether this is the production date of the table or pulley, but does help to identify roughly when it was made.

Something else I have noted that I think is interesting about the idlers is that some of these are quite eccentric except at the running surface and are apparently machined after molding so that there is no significant run out. I've seen ones that were perfect and ones that are so eccentric that one wonders.

Also I have seen several including my own that are not co-planar across an entire rotation, but bobble slightly - they run quietly unless the edge bobble hits the next step down. Adjusting the pulley height slightly may be OK in some instance. I am not certain whether this is a defect from the factory or the result of being left parked in a running position for a long time - note that there is no dent in the pulley and they run quietly. I've looked at or worked on a grand total of four tables, and two of those had pulleys that exhibited one or more of these faults. Mine has both, and so does one other - both incidentally play just fine.

A replacement idler would seem to be a good investment in such cases, but I have not been able to demonstrate that these issues actually cause audible or even measurable problems. (I don't have a wow&flutter meter and required test record so it would be hard to test this..)

Intermediate Pulleys:
I'm looking for a complete MKI intermediate pulley and spindle to see whether or not it can be retrofitted in my MKII, and results in a quieter table. As I commented a couple of days ago the MKI intermediate pulley is much quieter. It would be great if someone reproduced these components in an improved form.

The MKI intermediate pulley from the factory seems to have been equipped with a little removable plastic cap on top of the bronze bearing assembly. Note that when disassembling there is a tiny little ball bearing in the top of the bearing assembly that acts as a thrust plate and falls out when you do the disassembly - it will usually end up on the brake magnet, but not a good thing if it gets lost.

Oddball TD-124MKI might be a TD-121:
I got a call today from a friend who has a table he thought I would be interested in. Although it says TD-124 on the escutcheon it is equipped as a TD-121, no strobe, no clutch, single platter, 10mm bearing, and whilst not completely sure apparently a single speed intermediate pulley.. The serial number indicates it was originally intended to be or was a TD-124 MKI..

Odds & Ends
I'll be installing a motor upgrade kit (dual bushing setup) and a new main bearing in one of these tables in a couple of weeks. I'll post the details here when I do it.

As you know I am quite verbose, so anything I think of will get added here..

I'm listening to my TD-124 as I write this, very pleased with the sound - notwithstanding my MKI intermediate pulley envy..
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Old 9th December 2010, 07:52 AM   #153
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Click the image to open in full size.

Above is a photo of the (mk 1) step pulley axle with bearing ball parked at its top. This being where it runs when the step pulley is assembled over the axle shaft. The bearing ball is 4mm diameter and has been upgraded to silicon ceramic.

Click the image to open in full size.

Above: Prior to clean up......a detail shot of the casting detail that retains the step pulley axle. Two set screws. The MkII, and some of the later MK1 models do not use this casting detail.

Click the image to open in full size.

Next photo shows the vertical alignment between idler tire and step pulley. This one needs some adjustment. Just as a side note the idler wheel in this photo is one from Mirko. It spins very concentric to its axis of rotation and offers the benefit of new bushings. However I did see some lateral run-out. Not so bad as to impede making a good vertical adjustment.
Click the image to open in full size.

After the adjustment the idler tire ran cleanly within the width of the step pulley lands without touching a shoulder.

More details on this build at:
2078
serial number 2078. A very early TD124.

re; TD121
That should be interesting to note the detailed differences between TD124 and TD121. In additional to the loss of 3 speeds, a strobe, a level, and a clutch, the TD121 uses the 10mm bearing from the TD135 and its platter.

Anyway, I thought some photos of a TD124 build might be useful.

-Steve

Last edited by user510; 9th December 2010 at 07:58 AM.
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Old 9th December 2010, 12:13 PM   #154
kevinkr is offline kevinkr  United States
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Very useful I think, and the photographs are excellent. I will post some pictures of the oddball TD124/121 when I see it - it should prove to be very interesting.

Interesting comments on the MKI vs MKII intermediate pulley spindle arrangement. I will be looking at those MKI again in the coming weeks and will have a look at them. Given their serial # I expect they would be set up like the one you show.

Have you run one of Mirko's idlers on a table equipped with the zamac platter? The reason I ask is that both a friend and I can hear the idler exciting the platter resonance in our respective MKIIs.. Wondering if the idler might have hardened up sufficiently that a new one might improve on this situation.

I am planning on an eventual platter upgrade but have resisted buying one of the recent flood of vintage cast platters because I run an MC cartridge.
Do you have any experience with the Schopper or Mirko's non-magnetic platter?

BTW your motor bearings are very nicely & precisely made, it was obvious when I installed them..
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Old 9th December 2010, 07:11 PM   #155
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Quote:
Have you run one of Mirko's idlers on a table equipped with the zamac platter? The reason I ask is that both a friend and I can hear the idler exciting the platter resonance in our respective MKIIs.. Wondering if the idler might have hardened up sufficiently that a new one might improve on this situation.
No experience there. Although I have had one of those over here for a bearing refurbish.
Click the image to open in full size.
I took some photos and made observations at this link:nonmag

With regard to Mirko's idler replacements, I recall doing a direct a/b comparison between the original (but still very good) idler wheel and one I bought from Mirko. This was on #2729, my first TD124. (iron platter) What I heard with the new idler wheel was a perceivable lower noise floor and a slightly better sense of pace. The lower noise floor translates into improved detail reproduction. Of course these observations are just perceived and not measured in any way. Still, they were obvious enough for me.

Quote:
I am planning on an eventual platter upgrade but have resisted buying one of the recent flood of vintage cast platters because I run an MC cartridge. Do you have any experience with the Schopper or Mirko's non-magnetic platter?
No experience with either the Schopper or Mirko non-mag platters. Can't say anything about those.

But I can say that I have used some MC cartridges on every TD124 I've had over here (all with iron platters) and never experienced any issues with vtf or magnetic pull between cartridge and the iron platter beneath it. Probably the MC cart I have with the strongest magnet (a Shelter with neodymium magnet) was the best test for that effect that I gave it. But no problem there. I have to say that I have only tried a few different MC models. The Shelter. A few different DL-103 and R models. An Ortofon Jubilee. But I have not tried any of the Ortofon SPU models...of which some folks say is where the real trouble is...

Quote:
BTW your motor bearings are very nicely & precisely made, it was obvious when I installed them..
Thanks. Credit goes to a small tool maker's shop local to me. They do nice work and held the tolerances that I drew for them like it was all in a days work, no problem. But the negative side to that story is that they do charge real money for their work.


Anyway it is fun to watch your progress over here on this forum.

-Steve
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Old 9th December 2010, 08:09 PM   #156
kevinkr is offline kevinkr  United States
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Hi Steve,
Thanks for the insightful comments..

Particularly interesting to me is the comment on the DL-103 as well as other MCs and cast iron platters, hearing this I think I might actually give it a try when the next crop of cast platters show up on eBay then.. Worst case I can always resell it..

I've been planning on acquiring one of Mirko's new idlers at some point to try. My current one seems to work well, but it strikes me as a worthwhile experiment. Your perceptions if true would further improve the performance of a great TT..

I'm still having some minor belt related issues, although it is less than previously as the CB965 belt has stretched quite noticeably. It does seem that an occasional dusting with talc still helps, but that is a bit of pain.. The quietest belt is still the original, the Thakker is acceptable and is what I am using. The others are all quite a bit noisier, but oddly these same noisy belts run very quietly on the two MKI I tried them on.. Fellow MKII owner down the street is having the same exact belt issues, however I gifted him my worst belt, poor guy.. (It was the only spare I had at the time. They all improve at least slightly with talc and running time too.) None of this is "overtly" audible unless it's getting extreme during playback, but once it is finally eliminated it will probably be noticeable.

I'm going to take a look at some slightly longer belts and see what that does. Apparently these noise issues are enough of an issue that there is a camp of thought that advocates completely disabling the eddy current brake and using a variac instead to control the speed. (You have to drop the voltage pretty drastically in order to get it to run on speed) I'm not in favor of this approach although my limited experiments indicate it does reduce noise levels, but it also seems to reduce running torque significantly. I have not listened to one configured this way but if there is anything to the high torque argument I wouldn't think this would be the way to go..

Do you think that local model shop might be capable of making an improved less resonant version of the intermediate pulley for the MKII? I could be all wet here.. Seriously..
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Old 9th December 2010, 08:27 PM   #157
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Surely a better solution would be to feed the mottor a lower frequency instead of reducing the torque. I may be able to try it out, just not sure if my current regenerator has sufficient guts...
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Old 9th December 2010, 08:52 PM   #158
kevinkr is offline kevinkr  United States
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Quote:
Originally Posted by analog_sa View Post
Surely a better solution would be to feed the mottor a lower frequency instead of reducing the torque. I may be able to try it out, just not sure if my current regenerator has sufficient guts...

Would be an interesting experiment, my experience with induction motors is that they generally run smoother at higher frequencies than lower, in this case the reduction in frequency would be quite small, probably 1Hz or less. I can generate anything in the 50Hz - 60Hz range here without too much difficulty if your experiments indicate it works. (Actually I can borrow a source temporarily as needed.)
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Old 9th December 2010, 09:32 PM   #159
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Quote:
Originally Posted by kevinkr View Post
Hi Steve,
Thanks for the insightful comments..

Particularly interesting to me is the comment on the DL-103 as well as other MCs and cast iron platters, hearing this I think I might actually give it a try when the next crop of cast platters show up on eBay then.. Worst case I can always resell it..

I've been planning on acquiring one of Mirko's new idlers at some point to try. My current one seems to work well, but it strikes me as a worthwhile experiment. Your perceptions if true would further improve the performance of a great TT..

I'm still having some minor belt related issues, although it is less than previously as the CB965 belt has stretched quite noticeably. It does seem that an occasional dusting with talc still helps, but that is a bit of pain.. The quietest belt is still the original, the Thakker is acceptable and is what I am using. The others are all quite a bit noisier, but oddly these same noisy belts run very quietly on the two MKI I tried them on.. Fellow MKII owner down the street is having the same exact belt issues, however I gifted him my worst belt, poor guy.. (It was the only spare I had at the time. They all improve at least slightly with talc and running time too.) None of this is "overtly" audible unless it's getting extreme during playback, but once it is finally eliminated it will probably be noticeable.

I'm going to take a look at some slightly longer belts and see what that does. Apparently these noise issues are enough of an issue that there is a camp of thought that advocates completely disabling the eddy current brake and using a variac instead to control the speed. (You have to drop the voltage pretty drastically in order to get it to run on speed) I'm not in favor of this approach although my limited experiments indicate it does reduce noise levels, but it also seems to reduce running torque significantly. I have not listened to one configured this way but if there is anything to the high torque argument I wouldn't think this would be the way to go..

Do you think that local model shop might be capable of making an improved less resonant version of the intermediate pulley for the MKII? I could be all wet here.. Seriously..
And so it seems your belt issues continue. I am beginning to think that I can now point to a likely problem area. And it isn't the belt. The TD124 should be tolerant of belts of different tensions and widths. Rather I suspect that your MKII step pulley may be showing signs of having some bearing wear.

I have only seen one later style step pulley close up. That one was one that a friend brought over. It featured an entirely different bearing design than the earlier mk1 step pulley as I have pictured in the above post. Instead of an inverted thrust style of bearing it is more conventional in that the axle shaft is permanently fixed to the step pulley and that this axle shaft with step pulley attached fits down into a housing with two bushings and a thrust pad. Very much like a platter bearing.

The potential I see in this later design is that the axle bushings are located well below the belt crown of the stepped pulley. As such when the drive train is in operation with the drive belt pulling at it, there will be a kind of tipping force applied to the bushings and shaft. Result, higher degree of bushing wear.

But it is more complicated than just belt pull trying to topple the step pulley off its axis of rotation. There is also the force being applied from the idler wheel. Depending upon which speed it is normally running at this can counter the effects of belt pulley or maybe just complicate it into a more random pattern of wear between bushings and axle shaft.

Thing to check: excess slack in the running clearance between axle and bushings on your step pulley.

If it is the case, this would account for excess noise being generated by both belt and idler wheel.

My suggestion; Get fussy about the step pulley bearings. Make repairs before getting analytical about various belt qualities or even trying out another idler wheel.


-Steve
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Old 9th December 2010, 09:54 PM   #160
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