Restoring and Improving A Thorens TD-124 MKII - Page 13 - diyAudio
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Old 20th November 2010, 09:21 PM   #121
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The turntablebasics belt came today and measured more or less similarly to the Thakker belt, except that it is 0.030" thick and appears if anything to be somewhat less pliant than the Thakker. I haven't run the new belt yet so I will report back when I do. I'm in no rush to do it.
Another source of belts would be Joel Boltreux. Former Thorens employee who frequents the Vinyl Engine and offers support within the Thorens forum there. He sells various maintenance parts and supplies for Thorens players. I'm sure he has a TD124 belt. If you haven't already made contact with Joel, he is responsive to emails. He goes by the moniker 'Violette' I think I will ask Joel about the Thakker belt and if the one he sells is the same belt or if it is a different one.

Another source for Thorens belts is Rolf Kelch. Rolf is sometimes difficult to get in touch with. However he understands the vintage Thorens players and can source the original belt from the same belt factory in Lahr that produced belts for Thorens back in the day. Link to Rolf:
Rolf Kelch


I have purchased three TD124 belts from Elexatelier. Link to Elex:
Thorens Turntable Belts Record Player Audio Equipment Electronic Parts: Elex Atelier

These seem like a close fit providing you don't use them over the larger 50hz pulley. Making note that I recommend Elex only for the TD124 belt and not the later belt drive models like the TD160, etc.

At least there are some more alternatives for you to try.

-Steve




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Old 20th November 2010, 11:13 PM   #122
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Hi Steve,
I asked Joel about TD-124 belts some weeks ago, (I'm active at VE, tapeheads, and AA as well as here) he informed me that unfortunately he has completely sold out. He is also of the impression that there was a belt specifically for models sold configured for 60Hz, and another for 50Hz. I have not been able to find anything proving that is true, but Thorens does state in the last service manual that there is just one belt for 50 or 60Hz operation and all belts I have seen so far are about 12.1" when new, and stretch to about 12.8" or so when used but still ok. (Some belts are listed as actually being 320mm, but I've yet to see a one new out of the bag that was much over 300mm, probably a difference in the way I measure them. [untensioned])

Thorens lists two belts the CB908 and the CB965 in the service manual, but I believe the CB908 is just an older part number that was superseded by the CB965. (It's not clear to anyone unfortunately)

My original belt is virtually identical in length to the Thakker sourced Thorens CB965 as is the new belt from turntablebasics.com. They are all different thicknesses with the original being much thinner and more pliant than the other two.

What I come away with so far is that while they may all be the same width and length, they differ significantly by thickness and durometer. I currently have 3 belts and will eventually get one or two more for evaluation. Fortunately for the most part they aren't too expensive.

I suspect the belts Technical and General are selling are the same Thorens sourced belts that Thakker sells, but am awaiting confirmation.

I will check out Elexatelier, and Rolf Ketch..
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Old 21st November 2010, 11:42 PM   #123
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Exclamation One Very Temperamental Turntable

Tonight the unthinkable or in the case of a TD-124 the not so unthinkable occurred: It just flat out refused to run without a push..

I pulled the table out of the system, removed the arm and pulled the platter. Applied power and listened to the motor just buzz. A tap got it going. When turning by hand it seemed a bit tighter than I remembered. I applied some additional lubricant (turbine oil this time) and attempted to improve the alignment of the bearings a bit. It definitely loosened up.. This I think does not speak well of the bearings I installed and if it continues to be a problem I will clean and reinstall the originals. Word to the wise, the new ones may not be as good as the originals.

I'm also wondering about the 3 in 1 20wt electric motor oil, athough I observe no issues with the oil in the main bearing well which of course is not getting warm.

The oil in the motor is now a mix of turbine oil and 20wt electric motor oil, we'll see how that stands up..

I'm very concerned about the motor issue as an mtbf of two weeks is not very long..

This may explain why most E50 motor rebuilders run the motor for a week and disassemble, clean and relubricate after servicing them.

I unfortunately also discovered that overfilling the main bearing well is not as benign as some would have you believe, the oil eventually gets everywhere. I carefully cleaned up the mess, put everything back together to a cacophony of bad noises, and really poor performance - pulled it all apart and tried again - now it is about as quiet as before and starts quickly.

I will comment in a separate post about some of the other things I discovered relating to belt noise issues tonight as they ought to stand alone. See next post.
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Old 21st November 2010, 11:53 PM   #124
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Default Belt And Intermediate Pulley Noise

I made an interesting discovery as a result of my TD-124 refusing to run.

Basically I discovered that small changes in motor pulley height have a very big effect on the overall belt and intermediate pulley noise level. The table must be absolutely level when you do this adjustment, and the idler pulley should be removed in order to make it easier to perform.

Basically what you want to do is adjust the pulley height for minimum noise and you need to do this when the motor bushings are replaced and it probably would not hurt to check it from time to time.

I briefly evaluated all three belts I currently have on hand, and the original belt was still the quietest, the Thakker was significantly noisier, but the difference appeared not to be as great as previously was the case, and the noisiest belt of all was the one from Turntablebasics which might improve with some run in time.. This belt also seemed to fit more tightly than the other two and was not as elastic.. In operation the belt continued to exhibit the odd ripply appearance I noted when I got it. I would call this the belt of last resort..
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Old 22nd November 2010, 03:38 AM   #125
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Default CB965 Replacement Belt, Clutch Adjustment, Idler Pulley

Spent a little more time after dinner investigating the scraping noises when the clutch was engaged - it turns out that there is a very tiny difference in platter height with the original bearing cap and thrust plate and the new one which apparently is significantly lower.. The rear clutch finger apparently was adjusted just a little higher than the others and since the zamac platter is not precisely machined there was a low spot which was hitting on just this one finger. (run out is probably no more than 10 thou or so..) A very minor adjustment took care of that. Silent now.

I decided after coming back downstairs and hearing a fair amount of noise as I approached the turntable that I would try the CB965 belt I purchased from Thakker. I installed it and made some minor tweaks to the motor pulley height and I was able to get it reasonably quiet, on this front I am basically giving up as it's clearly hopeless - you'd have to be deaf not to hear the noise, but I have decided not to obsess over this any longer. The current Thorens CB965 belt is acceptable - in the long term if not I will just go back to the SME table I was using previously or get something else. Make no mistake this is an oddly noisy table, but the noise does not seem to get coupled to a significant degree into the platter as long as the idler is ok. Probably just not enough energy there to excite the platter given the huge differences in mass..

With all of the tinkering lately the idler pulley had gotten quite slick, so I treated it another wash in hot soapy water and a single pass with the scotch brite. This has returned the table to the very quick acceleration I remember when I first got it running.

The motor seems to be running fine and the bearing drag is greatly reduced.
This was observed after the motor had been off for about 45 minutes, so hopefully this will reflect to a completely cold motor as well.
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Old 22nd November 2010, 03:56 AM   #126
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Default Further Comments

This hasn't been a great day in the Thorens saga, but I suppose if you have several of them if one malfunctions at any given time you can just use another..

I'm fairly irritated at the moment, the saving grace is this thing is like a Ferrari, when it's right it's very right.. It just needs a little more help than I am used to - in fairness this table sat unused for 39yrs and to some extent resurrecting the dead might be expected to result in some issues of the sort I have been dealing with..

In retrospect of course I can see something was going on.. The fact that over the past few days it was getting more and more recalcitrant to run, and the fact that I could no longer adjust it to run on speed when cold might have been a hint. Increasing drag in the motor bearings was eating up precious torque, it still ran close enough to on speed when cold not to be noticeable until today, but today it was so bad I had to face the inevitable...

I thought I put enough oil in the new bearing assemblies, and these are aftermarket oilite bronze bearings so they are supposedly self lubricating. I'm going to have to keep an eye on these because they aren't behaving as expected. I added a significant amount of oil tonight and the motor is running as it did a couple of weeks back, hopefully I will not have to do this again quite so soon. Should I have to I may need to face the reality that I have to bake the old bearings, oil them, and reinstall them as it would then be apparent that the new ones aren't so good. In my zeal to address known and in this case obvious motor problems I may have created one, and I probably need to take this thing apart again and clean everything..

Right at this moment it is back to sounding great, creating a beguiling listening experience - its great strength.. Anxiety lurks in the background..

More coming of course..
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Old 22nd November 2010, 04:14 AM   #127
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Quote:
Tonight the unthinkable or in the case of a TD-124 the not so unthinkable occurred: It just flat out refused to run without a push..

I pulled the table out of the system, removed the arm and pulled the platter. Applied power and listened to the motor just buzz. A tap got it going. When turning by hand it seemed a bit tighter than I remembered. I applied some additional lubricant (turbine oil this time) and attempted to improve the alignment of the bearings a bit. It definitely loosened up.. This I think does not speak well of the bearings I installed and if it continues to be a problem I will clean and reinstall the originals. Word to the wise, the new ones may not be as good as the originals.
That's a major problem that indicates something very fundamental is not right. One can only guess, since you are the only witness. However it sounds as if the motor was seizing up due to excessive friction at the motor shaft to bearing interface.

I would not be too quick to point the finger of blame toward the new bearings. Prior to assembly one can simply fit a bearing over the motor shaft and observe the snugness of fit between bearing and shaft. Ideally there should be .0007 - .0010 inches of clearance between bearing walls and shaft.

Click the image to open in full size.

Click the image to open in full size.

Click the image to open in full size.

The worn bearings will likely exhibit a greater clearance than this. Not everyone is equipped to measure inside and outside diameters with mics and bore gages, in order to determine actual running clearances, but you can test fit the parts and observe any obvious excess slack or if the bearing seems rather tight and turns too stiffly.

Chances are high that your 20 wt electric motor lube and the so called 'turbine' oil (20 wt) are of very similar if not exactly the same formula. Either should work satisfactorily. Although I would certainly make sure that upon assembly both shaft, bearing and lube retaining felts are well saturated with the oil. Remembering that the Oilite bronze bushing material is of a highly porous and oil retaining type. The bushings need to be well soaked in oil prior to assembly.

Another consideration is that the bearing retainers and machine screw fasteners do not vibrate loose.

Click the image to open in full size.

I use a small dab of loctite thread sealer on the threads of each screw as a final touch to ensure a permanent joint.

I wonder if the shaft to bearing alignment hadn't shifted?

Presumably, the voltage commutator had been set for North American current. (100 - 120 vac)
Click the image to open in full size.

Above photo shows a mk1 set for NA current. Just noting this for anyone reading through the archives.

I think I would forgo any serious comparisons between drive belts until it is established that the motor is operating correctly and has been for a few weeks.

Belts will tend to stretch and become a better fit over time.
Setting drive pulley height should be straight-forward. Although it does make good sense to evaluate motor vibes versus drive pulley height by using a stethoscope to listen to the outer motor case, and chassis for each adjustment.

Lets not forget the motor mount grommets. If these are too soft, they won't hold the motor firmly enough to drive the step pulley/idler/platter without the motor twisting in its mounting. Such a situation might tend to lead one down false paths of analysis.

In other words....it should not be this hard.

re: main bearing lube.
The platter bearing. The mkII will be equipped with Oilite bronze bushings in the bearing housing. These are of the oil retaining type and do not require that the housing be filled with oil. However it doesn't hurt if there is a small volume of oil within the housing either, except when the housing is over-filled and upon assembly of the shaft, oil is displaced upward and into the interior space of the cast chassis. That's messy. Especially if oil is allowed to get on the drive belt or idler wheel...which will effect performance as well.

The other negative for having a volume of oil in the housing is that with the standard gasket and cover plate, the air pressure exerted upon assembly is enough to rupture the gasket and cause an immediate leak.

Prior to assembling the platter bearing shaft into the housing, I just apply some oil to the shaft and call that good enough. Perhaps a small amount is allowed to exist down in the thrust. More 20 wt.




-Steve
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Old 22nd November 2010, 04:58 AM   #128
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Hi Steve,
Thanks for the additional input. As long as the motor windings are intact I am not too concerned, as much of a nuisance as this is I can address the issue pretty quickly.

Yes my take on the bearings is that they were starting to seize, and the only likely explanation I have is that I did not add sufficient lubricant to the felts when I installed them. I have remedied that situation and will monitor and add a bit more if necessary.. It strikes me if I used insufficient lube the felts might actually wick oil out of the bearings.

All of the hardware is tight, I double checked. Bearing alignment is good.

I no longer have a mic so I can't measure the bearing clearances but there is no wear visibly evident on the shaft or original bearings.

The two lubricants I typically use appear to be different, the turbine oil is clear and has a viscosity I estimate at around 15wt sae, the other is the 20wt electric motor oil I have mentioned in previous posts, which is slightly golden in color.

The motor runs extremely quietly.. Time will tell as to what else I need to do to it.

The argument for filling the bearing well to a certain level is that the spindle then rides on an oil film at all bearing contact areas, but it is messy. I don't have the stock bearing cap and gasket at this point, and usually leave the spindle installed and remove the platter instead. I should note that the turntable as received had quite a lot of oil in the bearing well, (roughly comparable to what I now have in it) and this would have been as received since the table was never serviced prior to my receiving it.

The Thorens CB965 belt seems to be OK, based on the unverified conjecture that all is currently well. Only time will tell, and it only has a couple of hours of use so far. Pulley alignment definitely does play a major role. I think your comments on the bushings bear consideration and I guess I will order a set from Schopper sometime in the new year to try. The current bushings are definitely stiffer than the deteriorated originals.

Voltage range is 100-120V, and my line voltage is typically 118V..
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Old 23rd November 2010, 06:45 PM   #129
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Default A quick Update

It's been almost two days since I relubed the motor and made some minor bearing adjustments. So far after a running time of 20 hrs or so everything seems fine. It came up to speed very quickly this morning, and was exactly on speed within 10 minutes and has not drifted at all in 4 hours.

I will keep an eye on this issue and perhaps add some additional lube to the motor bearings in a week or so. I think I may have failed to sufficiently wet the new felts with lubricant, however this bears monitoring as it is not clear to me how new bearings with sufficient lube in them should have ran nearly dry in a couple of weeks unless the felts actually can wick lubricant out of them.

I removed the Thakker sourced belt this morning, it offends me that I can hear so much mechanical racket from a couple of feet away - the old belt is much quieter, however I do need to investigate whether the new bushings are in some way responsible for this, but observed no real deflection of the motor mounts when I install or remove any of the belts I have on hand, but that doesn't mean it isn't happening. There is no audible difference in performance of the table when playing records between the old and new belts so this belt is definitely usable.

Just idle speculation on my part, as I learn more I will post what I figure out.

I'm rather happy with the performance otherwise, and I am sure i will eventually get all issues sorted out satisfactorily.
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Old 23rd November 2010, 09:03 PM   #130
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Default Thorens 124 Neon Bulb (Off Topic)

Sorry for being off topic, but if you need a bulb replacement try this:

RCA 991 Light Bulb, NOS For Thorens Turntables - eBay (item 390212816218 end time Dec-20-10 09:07:20 PST)Click the image to open in full size.

I just got one and it works just fine. Don't forget to try BO price.

David
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