Dual 1007A turntable problems. RPM too low..worn out idler drive wheel?

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mikecandu
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Dual 1007A turntable problems. RPM too low..worn out idler drive wheel?

Post by mikecandu »

Hi,

I'm restoring an old Grundig radio and turntable. An overview of my project can be found in this thread in the projects folder.

viewtopic.php?f=9&t=131

While waiting for a step down transformer I decided to clean up the record player. It's a Dual 1007A. I noticed that records were playing a bit slow, so I downloaded the manual and set out to clean and lubricate bearings, pivots etc to see if that was the problem causing the slow speed. The whole process became a bit of a nightmare as even the motor stopped rotating when I first took it apart and reassembled it. After hours of stress I managed to get the motor and the turntable working . Unfortunately the low RPM issue still persists, in fact it's a bit worse now. I think the cause is this idler wheel that drives the platter.

Does anyone have any experience with these idler wheels? Can they be "rejuvenated" with any of the "rubber enhancing" chemicals? Is this part available on the internet? I did see some idler wheels on the web but without dimensions not sure if they would work.

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Hugo
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Re: Dual 1007A turntable problems. RPM too low..worn out idler drive wheel?

Post by Hugo »

I have a lot of experience with the Dual 1009 and 1019, I have a soft spot for those turn tables. No experience with the Dual 1007 and I can see it is quite different from the 1009 and 1019 but it does not matter, the principles are the same.

Idler wheel: check if it grips, if it does not slip that is not your issue. The diameter of the idler wheel is irrelevant to the speed, that is good to know.
My experience with the 1009/1019 is that the lubricant in the motor has caked up and to a lesser extend the lubricants in the platter bearing and shaft will make it worse as well.

You need to take the motor apart and clean it all up, then put oil in it.
The same goes for the shaft but use a lubricant that is intended for high pressure or high loads.
One good trouble shooting rule is that if it is worse after you work on it, always go back to the things you worked on. So I think it is your motor. Go back to it and make it turn smooth and feather light.

It is good to realise that Dual recommends a full lubrication maintenance every two years. (who ever does that?)
I do that according to the service manual replacing the 5 different lubricants you need with contemporary ones. This is a day's work but in many cases you can completely rejuvenate a non working Dual that is sold for parts only, like that. It is extremely rewarding if that's your thing.

When I have time, I may make a blog about it but I am on an extended business trip right now.

PS, I have never come across that but a bad capacitor in the motor can do that as well. The motor on the 1009 and 1019 (they are the same) is indestructible, some later Duals had motor issues (I believe they where all belt drive). I am not sure about the 1007 motor but my guess is that it is fine (besides the lubricant issue). The Dual 1009 was the first Dual TT that complied to the DIN 45500 HiFi norm. One of the differences with non HiFi models is that the motor on the 1009 and 1019 is magnetically shielded so no magnetic stray fields will interfere with the dynamic cartridge. So your 1007 motor will be a different one but also here the principals will remain the same.
If you want to completely overhaul your turn table, I would recommend to find a service manual which you have. There is a lot you can do to make it worse, pay special attention to the types of lubricants prescribed. I use sowing machine oil in the motor.
mikefc
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Re: Dual 1007A turntable problems. RPM too low..worn out idler drive wheel?

Post by mikefc »

my two cents; I agree with Hugo completely. I too love Dual and have both 1007, 1009, and 1019 in my house , all restored. There is a spring on the idler mechanism meant to keep the idler in contact with motor spindle and platter ring. If too loosey goosey the idler will slip. Also , of course , the idler could simply be hardened to the point of no return. Contact Gary at VoiceOfMusic.COM , he has all you need.
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papa-j
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Re: Dual 1007A turntable problems. RPM too low..worn out idler drive wheel?

Post by papa-j »

mikefc wrote: Thu Mar 25, 2021 9:16 pm ...... Contact Gary at VoiceOfMusic.COM , he has all you need.
Looks like the URL is https://www.thevoiceofmusic.com/default.asp Nice site.
Attempting to reduce ignorance every day (always starting with my own)
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mikecandu
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Re: Dual 1007A turntable problems. RPM too low..worn out idler drive wheel?

Post by mikecandu »

Mikefc

Thanks for the link. I did clean up the rubber rollers and idlers and lubricated with SAE 20 oil the points mentioned in the manual. Using "rubber renew" seems to be somewhat controversial on Youtube but 12voltvids used it in his Dual 1007 rebuild.

https://www.youtube.com/watch?v=fanwpm-f3p8&t=697s

I figured he seems to know what he's doing so I used it as well. Turntable speed has definitely improved but it's still not perfect.

ImageImage

The 33 RPM setting seems to be a bit better then the 45 RPM. I did find a new old stock motor on e-bay that looks like it will work but I think this is probably as good as it gets.

Mike
Hugo
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Re: Dual 1007A turntable problems. RPM too low..worn out idler drive wheel?

Post by Hugo »

33 RPM is fine for all intends and purposes. The 45 RPM is still too low. At 45 RPM, there is more motor torque required. I think your motor is fine but you might have to open it up once more and also ensure it is perfectly straight when you close it up again. If you want to replace stuff, then replace the capacitor with a safety capacitor of the same value. They are guaranteed to go in open when they fail so if it does not help, at least you made your record player safer.
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mikecandu
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Re: Dual 1007A turntable problems. RPM too low..worn out idler drive wheel?

Post by mikecandu »

Hugo,

So after reading your message I went downstairs and lubricated the motor and the platter spindle bushing with no real improvement. I took the platter off and made this video. Hopefully you can see the video with the link.

https://1drv.ms/v/s!AsJiko0hVbGsgYI4cqhLE88On4D43A

If I put a bit more tension on the spring the idler pulley seems to rotate in a more positive fashion i.e. more torque.

Mike
Hugo
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Re: Dual 1007A turntable problems. RPM too low..worn out idler drive wheel?

Post by Hugo »

So the Motor could be red herring and replacing or shortening the spring would be a good idea. The answer will be in the speed of the platter after you do that. I hope you are right, that would solve the problem. The reason I am curious is that the spring is mainly used to start up the platter. Once the platter is turning the motor is forcing the idler wheel tighter wedged between the platter and the motor spindle. The more torque is required the tighter the grip on the idler wheel. But lets see what happens, every trouble shooting session is an opportunity to learn.
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mikecandu
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Re: Dual 1007A turntable problems. RPM too low..worn out idler drive wheel?

Post by mikecandu »

Hugo,

So I made some progress here with the turntable, at least as far as figuring out what's available on the market. I could not find an original Dual (NOS) spring anywhere (Part # 11A-10). I did find one that looked very similar on e-bay. I sent that guy my spring measurements and I'm waiting for a reply. I did find a spring with near identical measurements on McMaster Carr so I ordered two of those and we'll see how that works out.

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The idler wheel is another story. I could not find the original Dual part#(31G-U72) as NOS anywhere on the internet. I did find a used one on E-bay but that might be worse then the one I have. I can get my wheel rebuilt by https://www.thevoiceofmusic.com/ . The price is reasonable but I'm kind of sceptical that their rubber renew/softener is that different then chemicals I can use at home.

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The most promising lead I found so far is a site in Holland called https://www.pickupnaalden-shop.nl/. They have my Idler wheel listed on their website as "out of stock" but they have a very similar wheel (11A-U48) that has nearly identical dimensions to my wheel. It looks like it's a compatible wheel. I will email them to see if they think the wheels are compatible and about shipping costs to Canada.

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Hugo
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Re: Dual 1007A turntable problems. RPM too low..worn out idler drive wheel?

Post by Hugo »

The axle thickness is different, you will have to make a bushing. That is possible if you have a lathe.
It can also be that the bushing height is different. You may have to McGyver something else there...

I would go with the rebuild service. I do not think they will just rejuvenate it but rather start with a cylinder of rubber and turn it down to the right size and thenvuganize it on the metal, something like that. Ask them, and then post it here :)
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