1218 too fast with centered idler wheel

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nonost
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1218 too fast with centered idler wheel

Post by nonost » 13 Feb 2020 17:32

Hi. The 1218 I've been dealing with is too fast. With the idler wheel at the middle of the pulley I got around 34.6 rpm...I have to lower the pulley quite a lot to get 33.3 rpm...Any ideas? I've cleaned the pulley, idler and plate carefully. The motor is also serviced...I tried another pulley with same results.

I can't get why is this happening.

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Re: 1218 too fast with centered idler wheel

Post by nonost » 13 Feb 2020 18:56

Another idler! I didn't try another pulley it was an idler wheel what I tried. Uups! Sorry

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Re: 1218 too fast with centered idler wheel

Post by nonost » 13 Feb 2020 19:03

The motor gets 154v. It's a 150v motor BTW (it is a Dual HS51, amp + 1218). I don't know if these 4 volts are a problem...

Cheers!

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Re: 1218 too fast with centered idler wheel

Post by dualcan » 13 Feb 2020 21:07

Hi,
All Dual turntables that were installed in Dual combinations such as the Party or P series, the HS, or the KA series always used 150volt motors (coils), These motors are always fed through the power transformer in these units, not directly from the mains. The reasoning for this move was to only require a fuse change over on the power supply of these units. The changers always got 150 volts therefore regardless if the unit itself ran on 220 or 110 volts. It would seem that you are now running on 240 volts mains and that might change the output voltage.
You must connect this motor to a 150 transformer.
Regards,
k

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Re: 1218 too fast with centered idler wheel

Post by mrow2 » 13 Feb 2020 21:22

I cannot tell if you are running it through the transformer or not, but it seems as though you are operating it as it was intended using the HS power transformer. I wonder if this could be related to the transformer itself?

Back to the slight speed issue, I do not have a certain answer but the following steps are good to perform regardless. Seems to me like you might possibly adjust the pulley height a tiny bit and also dress the idler wheel for a sharper contact on the pulley. Pulleys do wear out (the metal is rather soft), but chances are yours can be used. Maybe don't seek perfect centering of the pointer as 33 1/3 RPM, but rather a reasonable range on the dial and leave it at that. Also changing out the idler is usually irrelevant in the case of a speed issue; the maths do not depend upon an idler wheel being a precise diameter. It's the pulley and of course the RPM speeds which count. Maybe Klaus can find something I missed but I didn't want you thinking you had to keep trying different idlers. Better to have a good one which is properly "dressed." If the pulley has not been removed before, study other posts on pulley removal first before attempting it. It is critical you do not damage it, and also that you understand how to lift one off the shaft which has been stuck on for 50 years. Oh, you might also want to dress the platter drum as well, and avoid touching any of these surfaces with fingers after (finger oil = bad news for such surfaces). At least following these steps ensures good contact and minimal slipping in the drive system, always desirable.

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Re: 1218 too fast with centered idler wheel

Post by nonost » 13 Feb 2020 23:20

Hi! I'm using the HS51 power transformer, of course! It gets 220v and feeds the motor with 150v. Well, my meter reads 154v. So I would say that's ok.

I wouldn't worry with a 0.5rpm or so...but I have to lower the pulley so much that the idler wheel is just at the highest height possible. If I use the pitch control in order to lower the rpm, the idler would be off the pulley :S Something's wrong

It is really weird...I've dealt with slow duals but I don't know how to deal with this. If the idler is not the problem...maybe the platter is too soft. I mean, I use a fine sand papper on the rim (1200 grit) and the used a fine steel wool. Maybe it is tooo slippery...I don't know what to try.

Cheers!

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Re: 1218 too fast with centered idler wheel

Post by dualcan » 14 Feb 2020 01:51

Hi,
The idler can never cause a constant speed problem, as it has no influence on speed (power in = power out).
The diameter of an idler diameter therefore has no bearing. The problem must be the speed pulley, if the motor is not damaged. The motor temperature must never be more than 40c. on these types. An idler will however cause speed "wow" if it has a dent or deformation on the circumference
The idler grip on the platter is such that within one platter rotation, the desired speed is obtained. If there is platter slippage then the platter and idler need to be cleaned perfectly, until that one rotation is met.
Regards,
k

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Re: 1218 too fast with centered idler wheel

Post by nonost » 14 Feb 2020 11:33

Mmm...shouldn't a worn out pulley be slower? The smaller the diameter of the pulley the slower rpm. This one is faster. That doesn't make sense to me.

Thanks.

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Re: 1218 too fast with centered idler wheel

Post by dualcan » 14 Feb 2020 15:39

Hi
Certainly, a smaller diameter pulley will reduce the speed, but I have seen pulleys that had a coat of crud from the idler/dust etc. deposited on the surface, which increased the diameter. I doubt that you have the wrong pulley, although it can't be ruled out.
In any event, if the voltage is ok (154 is very reasonable), the motor coils not shorted (temp. around 38C) then the only thing to speed the drive, is the pulley. Taken for granted, is that the platter drive surface is spotless.
Regards,
k

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Re: 1218 too fast with centered idler wheel

Post by Bic 410 » 15 Feb 2020 00:56

How do you measure the speed? A phone application? How does it compare to a trusted strobe disc?

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Re: 1218 too fast with centered idler wheel

Post by mrow2 » 16 Feb 2020 20:22

Try different methods. Have heard that a phone is one answer; but I have not tried it. Mains current can affect it, my understanding (it's been written about in the forums ad infinitum) -- it can vary depending on the time of day. A platter strobe disc with flourescents nearby is a way of checking. I have read that there are inaccuracies checking strobes using house mains but I can't explain it. I think the early usage of pattern strobes on the platters were to be guidelines and perhaps not absolutes. I suspect the electronic direct drive and quartz lock units with strobes may be much more accurate (15-20 years of progress since the 1218 and 1228 designs). Trying to make it perfect at one particular setting (for instance, so that you could always set it at one mark to have it in tune with a particular music instrument of some type) might be unlikely given what I've read.

So ideally you do need that speed range normally offered by the right pulley and a motor performing as it should. Klaus says your motor and transformer are good. I previously mentioned the spotless, finger-printless cleaning of the idler and platter drum and Klaus (who taught me, eons ago) did too. That includes (gently but evenly) dressing the drum with a fine paper and then removing dust and debris with isopropyl. Repeat the isopropyl alcohol cleaning step. Dry it, and re-assemble without fingerprints. Make sure the idler suspension is in good operation - fluid and springy. My own little PDF Guide covers this extensively. This step would be absolutely last if you were to attempt the following:

Lacking a solid answer to this conundrum, It seems that a pulley, as it wears, would get smaller in diameter, but possibly unevenly so when observing it from top to bottom of the 33 step. Provided you can have (or can readily acquire) a good backup (spare) pulley, and with your motivation, I can see machining the most worn pulley the smallest amount (remember, that brass alloy material comes off almost effortlessly) to a slightly finer taper toward the high end. You would use nothing more than a fine emery paper for this, held with two fingers. Or, a fine emery board might allow more accuracy. The correct (US) grit might be 300 or 400. I might press-glue a 300 to a narrow emery board (for ladies' fingernails) and attempt this.

The thing about fooling with that is you should not do it while on the motor itself. But there really isn't any other reasonable way: I do know it is possible to isolate the motor from the dust by surrounding the shaft with masking tape fully over the deck opening, and having a patient partner hold a narrow upholstery crevice vacuum nozzle there, during this small amount of fine shaving, to prevent the dust from entering the upper motor bearing. Wear eye protection. If you do only a little at a time (it may only require one brief shaving), it would allow you to ease into a range without overdoing it. I would not try to get the perceived optimal 33-1/3 setting centered on the speed scale; I would only endeavor to give it a little extra on the lower speed range with very little removal. I have, in the past, dressed a couple of pulleys when striving for perfect idler wheel contact and I can state that the material comes off really fast, so be careful if you actually do wish to try it. The straight flat surface of a small board acting as a soft file, using extreme care, seems logical. You're really only interested in dressing the upper part of the 33-1/3 step on the pulley but you also don't want to affect it so much that there's another step there. Just the smallest amount.
Dual 1219 pulley c.jpg
(112.57 KiB) Downloaded 19 times
As a guess, this might be even too much.

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Re: 1218 too fast with centered idler wheel

Post by nonost » 17 Feb 2020 02:19

Hi! I use an app for android with a good phone. I've dealt with 1235, 1214, 1225 and 1218 models and the app it's pretty reliable. I've experimented how as I was servicing the motor and such the wow&flutter numbers improved for each model (within specs) and how a slight human error was also noted.

Right now the pitch knob sits in the middle and I can decrease the speed turning the knob all the way. But the idler wheel it is on its limit. A little tiny bit more and the idler will be slightly out of contact with the pulley. So it is not horrible.

I have to check if the behaviour it's the same for 45rpm and 78rpm though.

I think it's obvious that I need to dress the pulley and I will tell you that I don't feel like doing it. I don't want to screw it up. I'm getting numbers within spec (<= 0.09%), so I'm going to wait till I get another pulley in the future. It is nice to see the 33.3rpm all the time while measuring the speed. With the oher units (all <=0.15%) it fluctuates between two decimals.

By the way, when switching from 78 to 45 or 45 to 33 I hear a kind of 'booooiiing' as if the idler wheel bounces for a couple seconds. Also at 45 and 78 I can hear a periodical 'tud' 'tud' very faintly...At first I thought it would be a flat spot on the idler but it looks fine, I dressed the idler anyway but the 'tud' it's still there. I'm not worry cause I'm not having wow.

Thank you very much mrow2 for taking your time, I really appreciate it. As I said, I will try when I had a backup pulley ;)

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Re: 1218 too fast with centered idler wheel

Post by mrow2 » 18 Feb 2020 02:38

I’m glad you can play at 33.3 even if that is the limit. Having broken rules in the past I’d be tempted to have everything in place, devise the right tool, and shave that pulley a couple gnat’s eyelash-thicknesses-worth (Or three!) and do this but I totally agree not to bother with it if all is good. Regardless, I had fun working it out in thought and word-assembly. Cheers, Don

PS the thudding idler wheel During speed switching is not much of a thing (a little like grinding gears without having a precision clutch?); I’ve noticed it and anyway I think speeds should be changed when motor is off and the platter is not spinning. There would really not be a need to do it during record play.

Also- I never played with 50Hz pulleys or 60Hz pulleys with 50Hz mains so I don’t know if the answer lies there; maybe it does.

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