Dual 1249 Speed Issue

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Tinkaroo
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Dual 1249 Speed Issue

Post by Tinkaroo » 16 Jan 2020 14:25

I know that a solution to the double speed issue is in the works but in the meantime I've jumped the gun and bought an 860-1 motor which I hope to swap the stator on my 840 motor with once I have the parts.

I've found some pictorials and tips on changing the stator but have opened this thread to share my experience plus look for any tips and to post any possible questions that may arise once I begin the process.

I really like this turntable but the unpredictability and annoyance with the speed issue takes away the joy of just playing and enjoying records. #-o

dualcan
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Re: Dual 1249 Speed Issue

Post by dualcan » 16 Jan 2020 16:10

Hi Tink,
The (nearly) stamp-sized board is being tested and should be ready very soon. Our VE member in Toronto, is working hard to get the last kinks straightened before putting them out for us. I should receive a sample very soon. The first iteration was quite a bit larger. Getting an SM 860 is also a good move, as these are of course newer and possible, has less wear. Don't chuck that 840 yet! When you are ready for the switch, throw me an e-mail- I'd like you to try something.
Regards,
k

Tinkaroo
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Re: Dual 1249 Speed Issue

Post by Tinkaroo » 16 Jan 2020 19:59

I'm attaching some photos of the 860-1 motor which comes from a Dual 506.
Dual 860 Motor 1.jpg
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Dual 860 Motor 2.jpg
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Dual 860 Motor 3.jpg
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Dual 860 Motor 4.jpg
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Dual 860 Motor 5.jpg
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DualSpinsMyVinyl
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Re: Dual 1249 Speed Issue

Post by DualSpinsMyVinyl » 17 Jan 2020 03:46

Three years ago I was able to procure a 1249 from the east coast. I was also able to purchase an SM 860 motor (NOS) in the box at the same time, (both from ebay). When the 1249 arrived it suffered from the speed sickness, so I serviced the new motor before installation, no telling how long it had been sitting. Extraction of the old motor was fairly simple (service manual is a big plus) removal of the pully was not as difficult as expected, installation on the new motor was made easy after having made a jig out of heavy card stock to transfer the height position from the old motor to the new. Worked like a charm, did not have to make any adjustments. While I had it appart I serivced the variable speed change mechanism and discovered that the problem I had been having with it not wanting to make small speed variation was due to the small ball bearing in the top of the pully sticking sometimes and there for no speed change. So I wiped the ball bearing on a cloth moistened with a small amount of oil to just dampen the surface of the ball and I have not had that problem return so far. Just an observation: I attribute the almost new condition of the my1249 to the speed sickness, probably never was used, who wants to listen to the minute waltz in 30 seconds.

Tinkaroo
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Re: Dual 1249 Speed Issue

Post by Tinkaroo » 17 Jan 2020 09:16

Thanks very much for the help and tips guys! =D>

I have to wait for my motor and some other parts to arrive, after which I will service the motor and try to perform a couple of small experiments which Klaus has suggested. In some ways Klaus is a bit like Professor Irwin Corey or Bill Nye the Science Guy and likes to experiment! :wink:

The platter spinning at high speed makes LPs sound like Alvin and the Chipmunks on their 8th cup of expresso! #-o

Tinkaroo
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Re: Dual 1249 Speed Issue

Post by Tinkaroo » 25 Jan 2020 10:45

I changed to the 860 motor which I serviced by first dismantling and thoroughly cleaning the bearings. After drying they were then reassembled and re-lubed using Chemlube 201 Ester/Synthetic Oil.

It works fine with the original 840 rotor but I used the new 860 rotor along with its bearings and original pulley and mechanisms.

It works like a charm now! 8)

A special thank-you to Klaus for his expertise and invaluable assistance. =D>

nebulix
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Re: Dual 1249 Speed Issue

Post by nebulix » 21 Feb 2020 01:53

I'm starting to roll out the first versions of the motor speed fix boards (MSF). These are prototypes that we've been testing with the SM-840 motors in 1249, 601, etc., that solve the issue with fast motor takeoff on startup.
MSF1.jpg
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The next version of the board will be much smaller with surface-mount components and an optically-isolated solid-state relay.
MSF2.jpg
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The theory behind the fix is to inject 4V DC into the motor stator for the first 1/2 to 1 second of startup. The delay is controlled by a tiny microprocessor that triggers a relay.

The mod is a kit that attaches to the underside of the deck plate. Installation is fairly straightforward, by attaching three wires with push-on terminals.
MSF3.jpg
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I have ordered a bunch of parts for the next run of boards. They come from China, so it's anyone's guess how long they'll take to get here. In the meantime, I've been laying out the newer SMD boards in CAD.

In any case, if anyone is interested let me know as I'll soon be offering these modifications to VE members at a reasonable price. Certainly much cheaper than replacing the motor, and it really does work.
More on this soon.

dualcan
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Re: Dual 1249 Speed Issue

Post by dualcan » 21 Feb 2020 02:55

Hi,
I can attest that this board works perfectly, as I have had the pleasure of testing the first pre-production board on a sick 601 I have: It will be extremely easy to install as I found out, as only a wire jumper between the power box and power switch is to be removed and the board plugged in its place, plus a single wire added to the connector box. Two wires simply plug into that connector box and one into the power switch, replacing that jumper wire.
My test results have shown no adverse effects on motor temp:
19 Temp test.JPG
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over a six hour "on" period.
Voltages and the necessary delay thereof are spot on:
23 Voltage test within 1 second.JPG
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24 Voltage test post 1 second.JPG
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The motor accuracy can now take hold as the synchronous section of the motor now takes control offered by the 60 Hertz line frequency.
This board will correct all the sm840 motors found in the 502, 510, 601 and 1249 turntables.
I was well pleased with the results and can heartily recommend it!
Regards,
k

Tinkaroo
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Re: Dual 1249 Speed Issue

Post by Tinkaroo » 21 Feb 2020 10:50

That is very good news indeed guys! =D>

It should be a lot easier than changing the motor, if one can even find an 860 motor at a reasonable price these days. #-o

DavidKotzebue
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Re: Dual 1249 Speed Issue

Post by DavidKotzebue » 23 Feb 2020 06:21

That is good news. I guess I'm mildly surprised after all these years there are still units with the 840 motor. I use an AR-XA in my office and am always pleased to use the 1249 in my home system. So simple - flip a lever and everything just happens! And in my opinion, the tonearm is quite an elegant piece of engineering.

Tinkaroo
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Re: Dual 1249 Speed Issue

Post by Tinkaroo » 23 Feb 2020 12:24

DavidKotzebue wrote:
23 Feb 2020 06:21
That is good news. I guess I'm mildly surprised after all these years there are still units with the 840 motor. I use an AR-XA in my office and am always pleased to use the 1249 in my home system. So simple - flip a lever and everything just happens! And in my opinion, the tonearm is quite an elegant piece of engineering.
Unfortunately many fell through the cracks and never got fixed but it is q fairly common issue which may just pop up intermittently but sometimes gets worse and more frequent.

Yes I agree they are engineering marvels and the tone arms are great! 8)

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