Dual 701, handle complete don't return back

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tapsa
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Dual 701, handle complete don't return back

Post by tapsa » 05 May 2019 17:47

Hi,

I think my issue is with some spring that should return no.134 (216 791) back if moving tonearm by hand (manual start). But I don't find any spring and can't figure out what is wrong.


This is how it should return:
IMG_4437 (2).JPG
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In this photo the tonearm is at the end of record:
IMG_4433.JPG
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This is when the tonearm is back in the rest position. No return of "handle" and not switching off the power:
IMG_4436 (Muokattu).JPG
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Anybody have had same kind of issue? Every part looks fine and no bending or other kind of damage seen anywhere.

I think this issue came after I tried what lift screw does. I think it should lift tonearm. Could it cause this? Dual 701 does not have VTA, so I thought if I could raise tonearm a bit. I have Shure V15III LM cartridge but I can't get tonearm in balance when playing record. This is weird because that is the original cartridge which Dual has combined with tonearm.


-tapsa-

tapsa
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Re: Dual 701, handle complete don't return back

Post by tapsa » 06 May 2019 17:26

I took short video clip to show what I mean:
https://youtu.be/iXjgN0FE26A

I dare not to do anything before I know what is the real cause of the problem.

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mrow2
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Re: Dual 701, handle complete don't return back

Post by mrow2 » 06 May 2019 18:09

I had spent about 20 minutes creating a reply, and lost it because I clicked the wrong button. Crikey, I hate it when that happens! All models, after decades of aging and exposure to the elements, develop some unseen corrosion and dirt as well. This inhibits levers in this design from sliding around like they did when new. A lot of models exhibit this type of symptom and it's often related to any area where levers touch one another (older lube dries up, dirt gets in, the corrosion etc).

One way is to separate and clean areas like this. One common location seems to be an issue repeatedly across many model designs; that of the Grooved Shaft (147) otherwise known to us as Main Pivot. It gets tight with all the above stuff and inhibits movements. New lube there won't fix it long term. Best way is to gently disassemble (take pictures along the way) and reassemble after it's been cleaned. Be sure to protect the delicate areas like tonearm gimbal and cartridge (remove it) etc. Let us know if this helped or not. Also check the tight areas right where the lever is attached underneath. ~ Don
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Dual 701 underside sm a.JPG
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mrow2
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Re: Dual 701, handle complete don't return back

Post by mrow2 » 06 May 2019 22:27

I had skipped looking at the video earlier. What I said about the main pivot is correct, but in this instance it seems fairly clear the specific parts attached to the lever and shown in the video have tarnish and dirt on them. Cleaning first, then polishing/buffing the parts with carnuba wax or car polish, then careful reassembly, should fix the issue. Don't bend any parts.

tapsa
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Re: Dual 701, handle complete don't return back

Post by tapsa » 07 May 2019 19:35

Thank you mrow2 very much. Now I have disassembled everything. That handle is not damaged. It also moves fluently. That's not the culprit I think:
IMG_4539 (Muokattu).JPG
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Also the main pivot seems good:
IMG_4541 (Muokattu).JPG
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Here's all the parts that I have cleaned well with isopropanol:
IMG_4536.JPG
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I think now I am in a big trouble. Don't know how to get that little spring loaded part back to switch level. This Dual 701 seems to me as a Swiss watch, you have to be almost watchmaker to get everything working if something has gone wrong.

I'm really grateful to Dualcan of his advices in this forum. When I serviced cam, I had never noticed a little toggle spring (117) and what silicon oil should be used in shut-off slide combo (ak 100.000) without his guide book "Servicing Dual Turntables: Cam and Cycling Problems".

So I'm not sure what is wrong. I hope to have time tomorrow to assemble everything. I didn't know I could polish those copper parts with car polish. A good advice.


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mrow2
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Re: Dual 701, handle complete don't return back

Post by mrow2 » 07 May 2019 19:58

I am surprised you have removed so many parts at one time. Hope you took a great number of pictures as you disassembled. The polish can help the steel and copper part to glide more smoothly. Be certain to remove the polish residue completely, use Alvania on the main cam and follow the SM to lube the remaining points. Less is best.

tapsa
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Re: Dual 701, handle complete don't return back

Post by tapsa » 08 May 2019 18:53

Everything is assembled now but still something is wrong. I think the culprit it that little square piece (part 135 in SM). I don't know in what position it should be. Perhaps just like in the picture? Here's parts diassembled:
square_piece_219049.PNG
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tapsa
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Re: Dual 701, handle complete don't return back

Post by tapsa » 12 May 2019 19:39

Okay, that "quare end" was not a problem, but too much grease was! Now it's okay. Anyhow, something is still wrong with automatics. Tonearm don't move as it should. Now it starts moving and then returns back.

I'm learning new things all the time, so I would like to know where is "eccentric". I don't understand which part of control arm it could be. Here's a picture from service manual:
pawl.PNG
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Would someone please be so kind to explain me where eccentric is and what effect it has to automatics?

I place also a picture from my Dual before I did anything and one picture the cam wheel removed. Now after cleaning everything and lubricating all looks out as it was when automatics worked.

The main reason for opening it was that motor stopped running, automatic worked ok. Now motor runs (one transistor had failed) but automatic don't as it should. I can't figure out what has changed. Everything should be ok. I have lubricated all moving parts according to the SM. I think there is something wrong with that "handle" or "pawl", what ever it is called.



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Dual 701 under cam wheel.jpg
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Dual 701 underneath.JPG
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tapsa
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Re: Dual 701, handle complete don't return back

Post by tapsa » 04 Jun 2019 19:43

Hi for a long time. I have ordered some new parts from Dual-Parts and changed them:
IMG_4616.JPG
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I oiled bronze bushings with Technics spindle oil SFW0010. Now main pivot is perfect, no excess clearense because of wearing.

Still problem with automatics. Should friction plate look like in the picture?:
friction_plate_227108.JPG
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Should it be bended like that?

As you can see, I'm not in a hurry repairing this Dual 701 because I have Technics SL-1700 mk2 what works fine. Anyhow, I really want to get this Dual working some day.

-tapsa-

DSJR
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Re: Dual 701, handle complete don't return back

Post by DSJR » 05 Jun 2019 21:13

Yes it should and it's an individual adjustment which will vary from sample to sample..

I cant answer any of your other issues I'm afraid. My 701 is flawless, almost silent in operation and I seriously don't want to upset it as the speed-accelerating issue has abated in recent times.

tapsa
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Re: Dual 701, handle complete don't return back

Post by tapsa » 06 Jun 2019 18:18

tapsa wrote:
12 May 2019 19:39
Would someone please be so kind to explain me where eccentric is and what effect it has to automatics?
I found out what eccentric is:
IMG_4633.JPG
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That screw really turns! Learning all the time more and more of mechanics :-)


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ulyssewang
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Re: Dual 701, handle complete don't return back

Post by ulyssewang » 04 Nov 2019 17:23

Which screw in the picture? And what did you do to make it work again? I'm having similar issue with auto start. Return works.

Thanks!
tapsa wrote:
06 Jun 2019 18:18
tapsa wrote:
12 May 2019 19:39
Would someone please be so kind to explain me where eccentric is and what effect it has to automatics?
I found out what eccentric is:
IMG_4633.JPG
That screw really turns! Learning all the time more and more of mechanics :-)


-tapsa-

mrow2
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Re: Dual 701, handle complete don't return back

Post by mrow2 » 04 Nov 2019 18:00

Where is your steuerpimpel in all of this? 701 is so forgiving and precise that it can almost function without one, but it still is a required part when all is said and done. I have not seen that you've checked or mentioned it in the discussion.

tapsa
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Re: Dual 701, handle complete don't return back

Post by tapsa » 05 Nov 2019 16:48

Thank you mrow2 of your reply. Anyhow, steuerpimpel is ok.

I have left 701 as it is until I get the motor aligned. I have changed so many parts in it that I'm sure it has to be adjusted right with oscilloscope. I dare not to do it myself, so I wait to get some of my friend more familiar with electronics to do the job.

I'm not in a hurry, my Technics with at440mlb works fine. I'm planning to use Dual 701 with my "Voima OP-3" Ortoperspekta amplifier when I get it adjusted right.

-tapsa-

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