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Dual 721: EDS-1000-2 don't start

Posted: 15 Mar 2018 17:41
by morg_wn
Hello Vinylengine community.
My name Is Boris, i am from St. Perestburg, Russia. And now i have problem with Dual 721 motor (EDS-1000-2). Before i begin: sorry for my bad English, and extremely bad technical English
So, i try to describe the problem: the motor don't start at 4 points of it's place. I.e. it's lokeed like one of four phase windings is not provide torque.
Here is short video (yes it is vertical(((, i saw only after recording):
As you can see, i can put tonearm from the tonearm-rest and turntable start rotating, but if starting position of motor was as at video (yellow mark near strobe window) motor don't begin rotating. the same situation if i rotate plater for 90/180/240 degree from this position - theese is a dead zone. Start from all other position - ok.
I think this is the cause why WOW and Flutter is very high/ i can't received stable speed, and this is not so comfortably for usage.

Any help, or ideas how i can repair it will be great! This must be easy work, but...nightmare for me right now.

More details what is already done:
1) All electrolytic caps are replaced, i changed 470uf for 1000uf/50 V, and both other for 47uf/50v
2) Tantalum caps is also replaced.
3) I replaced all three zenner diodes (ZD36,ZD7.5 and ZD15). Also i recplace all 1N4001, i think this is not important, but i want receive extra stable power supply (i replace it with the same 1n400x from Russian factory)
4) Of course, I cleaned speed selector and picth pot wery carefully.
5) I re-lube EDS-1000-2. This is vety important for reduce WOW/Flatter.
Here is data for EDS-1000 mk1 that's i also re-lube:
Before 0.1160% RMS weight, 0.2136% quasi peak within 10 second.
After cleaning and change oil: 0.0540% RMS weight, 0.0994% quasi peak within 10 second.
This data received from motor without adjustment, just for compare result before and after. Used Bruel and krejl test LP, Shure M92/ jico needle, 1.5g tracking force
6) I checked T3-T7 transistors - all worked
7) AA143 diodes showing that's they are ok.
8) Yes, RIFA cap in power section replaced
9) I re-soldered printed board.
10) Checked resistance between points no12/10/6/8 and ground, all is about 53 Ohm
11)Checked voltage drop at HALL elements (between points 4 and 2/3), now i forgot numbers, but it was the same as at working EDS-1000 mk1.

P.S. Yes, I try to use google, but don't find problem like I have.

Re: Dual 721: EDS-1000-2 don't start

Posted: 15 Mar 2018 18:53
I think you may need to contact the German Dual site forum (or ask Dualcan (Klaus) directly here by PM). I'm ok with the mechanicals of Duals, but not the electronic fault finding other than basic component replacing. I'll point him in the direction of this thread and see if he can help...

Re: Dual 721: EDS-1000-2 don't start

Posted: 15 Mar 2018 21:28
by morg_wn
Thank you. I will write to Him right now.

Re: Dual 721: EDS-1000-2 don't start

Posted: 15 Mar 2018 22:07
by Dual_Jean
Hi Boris and welcome to the forum.

I see you changed a lot of parts andI have only one question for you.

Was the problem there before you changed parts?

Re: Dual 721: EDS-1000-2 don't start

Posted: 15 Mar 2018 22:46
by morg_wn
Dual_Jean wrote:Hi Boris and welcome to the forum.

I see you changed a lot of parts andI have only one question for you.

Was the problem there before you changed parts?
Hello, i received turntable with follow problems:
No stable speed obtained - i replaced all EL. caps, cleaned swithces and re lube motor. Replaced RIFA (because it was not good, as always) This is my first iteration.
Owner says- that all is good, but turntable don't start sometimes (but He also says, this problem with this 721 from moment, when He buy it in Italy i.e. it was always) After half of year, after i serviced another 721 for Him, this one return to me, reason: sometimes speed runaway.

I checked-yes, but not always, sometimes it can drift, sometimes more less. I replaced diodes, and tantalum. Diodes- because it was helped at previous 721 and i read about this at VE. Tantalum - I desolder it out for checking, it was at limit of +- 20% tolerance, and i replaced it also. This is condition right now, it works with 33 and 45 rpm, but wow and flutter is to much for EDS, and little speed drifts can be obtained (but not always).

And after all i want solve problem with start (that was always be here, but i not saw it at first - my luck platter always stoped at good place for next start)

I.e this problem was with this turntable always, it is not appeared after I change some or one of part.

Re: Dual 721: EDS-1000-2 don't start

Posted: 15 Mar 2018 23:09
by mrow2
Klaus has advised us in the past that this motor is sealed and is not to be disassembled in any way, nor is it supposed to be lubed. This is an electronic motor, supported by semiconductors on the board, and the lube is a lifetime design. If I recall correctly, Klaus indicated that disassembly of the motor would result in unsatisfactory performance.

Re: Dual 721: EDS-1000-2 don't start

Posted: 15 Mar 2018 23:23
by morg_wn
Absolutely no. If you opened all old EDS-1000 you can find thats oil is dryed an polymerized. Inside main hole between two bearing placed felt pad that's must be filled with oil. After years and years- only polymeresed parts inside and metall dirt, if motor long used without oil. And as i write at the first post quality oil refill radicality reduces WOW and FLUTTER.
Ofcourse only clean oil for plain bearings must be used here, no motor or gearbox oil with active cleaning addictions.

Yes, motor can be damaged when you disassembley it, but as i write before- this problem was before i do something with turntable, and by oil condition, i was the firts who opened it (except at factory).

Only one spindle that's i don't recommend opened at house: micro seiki SX-1500 spindle (BL-91, RX-1500 and others) Because it filled with oil under pressure, and it's not easy re build it.

Re: Dual 721: EDS-1000-2 don't start

Posted: 16 Mar 2018 08:39
My 701's main bearing is full of a black coloured grease and I accessed it by removing the bottom bearing cover, NOT by adjusting the screw adjustment for height. Since there was no sign of any wear whatsoever in the thrust plate, I put the bottom back and left well alone.

Revox/Studer also used a version of this motor (I don't know how different it is electrically) and maybe some help would come from there.

Re: Dual 721: EDS-1000-2 don't start

Posted: 16 Mar 2018 09:38
by morg_wn
Yes, you right, never touch the height adjustment screw if you don't sure thats it what you need, just pull off bottom cover. But i talked not about grease at bottom, my post was about liquid oil at wall of bearing.
You mean this point:

I said about (side walls? sorry, don't know, how it named, but here pictures of Sony PS-X9 and denon DP-2700 where i marked this part. I just don't have Dual EDS picture right now)

Re: Dual 721: EDS-1000-2 don't start

Posted: 16 Mar 2018 13:30
by Legrace
Perhaps thread link below may be helpful. Refer to replies by member Dualcan.

viewtopic.php?f=37&t=96905&p=821044&hil ... F2#p821044

Re: Dual 721: EDS-1000-2 don't start

Posted: 16 Mar 2018 13:40
by Dual_Jean

I don't know where exactly your problem is but I would think that the uncontrolled WOW & Flutter is caused by a mechanical restriction to the motor OR some damaged windings of the motor.

What I mean by the mechanical restriction is IF one bearing is a little too tight then the motor will have a mechanical resistance to fight against and will cause excess WOW & Flutter.

You also mentioned : "So, i try to describe the problem: the motor don't start at 4 points of it's place. I.e. it's lokeed like one of four phase windings is not provide torque."

If I understand the DD motor concept correctly, (see attached picture) The odd (1,3,5,7) windings numbers are working together and same for the even (2,4,6,8) windings. If you are missing the odd or the even windings then it would explain why the motor does not start at 4 points and also the excess WOW and flutter.

I'm not an expert of motors but just saying...

Re: Dual 721: EDS-1000-2 don't start

Posted: 18 Mar 2018 10:47
I've been in touch with Klaus on another Dual matter and mentioned this concern.

Update which I hope I can pass on is that he's getting some fresh 1019/1229 type motor bushings/sleeves made and has nearly finished compiling a parts inventory of remaining Dual parts in Canada. This and other family matters have kept him away.

Back to the 721 motor. Apparently this isn't the first time it's happened as someone on the German Dual board had this issue too. Klaus has promised to do some digging to find the issue and solution and it is *possibly* to do with the coils and their connections, which you've probably already gathered. My 701 has a black grease all around the bottom 'thrust plate' and rounded spindle tip of the main bearing spindle. Maybe this was changed to a conductive 'oil' in the mk2 version as used in the 721. The brass/bronze side supports to the rotating spindles are usually referred to as 'bearing sleeves' I gather and that's the term I use.

In the meantime, PLEASE don't dismantle the motor until some expert help has arrived. I think the main issue at the time is that faulty motors were returned to the manufacturer rather than serviced out in the field. I remember a couple of 701's with iffy problems and at my first employer, I kind of inherited a 701 with speeds that occasionally dropped down before recovering for several minutes. I left the 'boxed' deck complete with all parts there when I left (stupid me) and it was probably junked when the business moved as the true delights of the 701 and later 721 weren't fully appreciated until years later, when people started siting turntables better and fitting better pickups to them, but I digress.

Please be patient, If the deck runs reasonably after a push-start, can you run it like this for a while until a definitive answer comes along?

Re: Dual 721: EDS-1000-2 don't start

Posted: 18 Mar 2018 11:00
P.S. Regarding speed accuracy of these decks in good running order. Given that mine currently takes ten minutes running to fully stabilise (there's a thermistor on long 'tails' I need to re-locate after lifting the board for cap changes), I have an external 'Linn' strobe disc and hand held light running at 300Hz to check speeds (easy to anchor ones hand on the plinth while watching the strobe lines). It's too accurate for many lesser decks though, such as Regas which all run slightly too fast and easily shows just 0.3% inaccuracy. In the case of the 701 and relatives, as well as two Technics SL1500's I've had here for a goodly while, the decks themselves hold speed perfectly, but the MAINS FREQUENCY here drifts off a bit at various times of the day and as the strobe light (glimme-lampe) is locked to the incoming mains, it indicated the decks have drifted off speed slightly when the external battery operated strobe shows they're just fine as set...

Sorry to thread drift. I appreciate the above isn't what we're talking about, but I thought I should share my experiences here on this.

Re: Dual 721: EDS-1000-2 don't start

Posted: 18 Mar 2018 23:36
by morg_wn
The first: thank for all who read my posts and send comments.
Legrace Thank, I read this thread, but it not helped here
DSJR thank for many info and spending your time

At last day I had a long dance with this 721. Spoiler: still don't working correctly.
Let's begin.
1) I was inattentive, before i wrote that's turntable had 4 dead zone (i.e. one winding without torque), now i passed a whole circle, by shifting platter by about 22.5 degree. So i find 8 dead zones, that's mean 2 winding don't provide torque. I recording new video, Corresponding to the service manual, it is like windings (1 and 2) or (3 and 4) is not worked correctly.
Also, i don't forget about wow & flutter, here is short video
Now W.&F. about 0.14% This is too high, yes, it is possibly to hear music, but no HI-FI quality.

2) I re-soldering windings connection inside the motor parts (I do it after ending paragraph 1 in this list) - no changing, but i can't re-solder or checking second hall element, no acsess to it without complete disassembly of motor - I think this is not' that's i must to do.

!I must ask: it's forbidden to use links to external resources? I posted schematic from another forum and link to wegavi.... Now my message corrected, i forgot rules?!

3) So.... If, problem still don't solved, i think: "let's analys from begin".
I measured windings resistance, results are follow:
W1 (test point 12 to ground) 57.3 Ohm
W2 (test point 10 to ground) 59 Ohm
W3 (test point 6 to ground) 59.1 Ohm
W4 (test point 8 to ground) 57.6 Ohm
Looked excellent, two pairs- 59 and 57 Ohm, not looked like a interturn short circuit.

4)It is time to check Hall elements. I connect oscilloscope to terminals before and afrter hall elements: ground to point no 4 and and signal wire to point no 2 or 3.
And i receive follow picture from both hall elements,
As you can see, voltage changing in both hall emelemts, but ampitude is very difference. I checked schematic, and think, that's variable resistor R13 for adjusting symmetry of hall voltage. By adjusting it, i receive follow pictures, i think now they are symmetric:

5) After i think, let's check volage waveforms at widings, I connecting scope to ground, and sigal wires to terminals 6 and 8 ( i have 2 channel scope)
Very clean sine waves is obtained
After, i checked windings no 1 and 2, terminals 12 and 10, picture is follow:
Really terrible, more like SAW style.
Again, let's compare it, one signal with sine wave (point no 6) and one with SAW-sine wave (terminal no 12)

6) hm....for today, that's all, i thinking what is the cause... Because we don't have any service manual to EDS-1000-2, i don't know how correct my mesurments. But how i understand, HALL elements is working, and problem must be easy solved.... but i don't understand how.
Also, i checked varible resistors R8 and R27 - they worked correctly.
Here is my working schematic, i mark windings that provide SAW-SINE waves.....

7) tomorrow I'll measure current betven points no 13 and 14....forgot to do it before.
hm....and for confirm thats windings 1 and 2 is not working correctly, I de-solder it, and will check rotating.

Re: Dual 721: EDS-1000-2 don't start

Posted: 22 Jun 2019 13:10
by valerjan
Hi, Boris! Did you manage to repair the player? My eds100 seems to have the same symptoms :(

Вам удалось отремонтировать проигрыватель? У меня eds100 похоже те же симптомы :(