new motor unit adventures...

71 views
Skip to first unread message

al

unread,
Jul 20, 2020, 6:22:34 PM7/20/20
to Gale Audio
Hello possibly diminishing group of people with Gale turntables!

This is how I spent lockdown...

Simon sold me his two turntables several years ago, with a spare dead motor unit. And at some point the encoder disc was broken. I haven't even got close to getting a new one from Litton, so I thought I'd try and rig another motor up with a good direct drive motor that fitted the space available. And since I had no control unit I could make one from scratch... Here is how it went, in many steps! I will write it as a recipe:

1. The initial step of removing the motor electronics (easy) and getting the main bearing out of the sub platter (needed a vice and strong pliers!). The soft metal insert inside the platter with the magnet on it eventually detaches from the platter with some torque, and then unscrews from the bearing assembly. At this point we were well past the point of no return and the old motor is toast... Coils pulled out from the motor housing.

2. I though about which DD motor to use and the Dual EDS 500 seemed a good fit: fantastic speed figures, apparently virtually no drift, good torque, and it fits! And they are fairly plentiful on ebay, around 70$ with the control board. This is absolutely essential, ideally with the potentiometer. Works on 21v DC which is a common switch mode laptop supply voltage, so power supply is easy.

3. The dual has wires to go for a switch for 33/45 so switching is easy with a relay. Arduinos are cheap (10$) and east to interface with a relay board so why not run everything with one? Also, there's an arduino library specifically for capacitative touch sensing, so dead easy to wire up a touch switch with no additional hardware (https://www.hackster.io/amalmathewtech/touch-controlled-light-using-arduino-d2f878) - in fact I just made the fine speed control potentiometer the touch switch and put a perspex disc on it. Finally, it is also very easy to interface a hall effect sensor with an arduino, so why not do a speed feedback sensor for the platter and measure speed once per revolution (the precision engineering for anything more instantaneous is well beyond me). Finally, 4 segment LEDs are easy to run from an arduino. The only tricky bit in the program is using interrupts (triggered when the hall sensor detects) to measure speed accurately, but I'd happily share the 5 lines of code it takes...

4. I put the controller in a pice of stainless tube topped with perspex, and made a cover for the bottom of the motor from 89mm stainless exhaust tube (which is cheap), both polished with a drill and rotary sandpaper. A disc of perspex glued to the potentiometer recreates the Gale look, but not too slavishly! Ethernet wire is ideal for control unit to motor: 8 cores (4 for dual motor, 3 for hall effect sensor, one spare). The sensor needs a little drilling of the motor housing to create a little space for it - easy because it is aluminium. 

5. the sub platter will sit on the spindle of the dual motor and centre with gravity in the small hole for the spindle at the top of it. That is the first piece of luck in centring. The dual motor also comes with a collar to mount its platter, and we machined the soft metal insert of the sub platter to accept this. The sub platter is then quite easy to centre accurately, which I did with some silicone glue in place. I didn't actually glue the subplatter to the dual motor: instead the collar slides on and the hole at the top of the sub platter locates on top of the dual spindle (the pictures may explain this more easily). There is then enough friction between the collar and the dual spindle to fix the two together (but allow platter removal). 

6. Finally, some rubber bands and silicone to locate the motor in the motor housing, a tiny magnet for the hall effect sensor on the sub platter and an ethernet connector on a perspex disc for the bottom of the motor housing. 

Much troubleshooting, fried voltage boards (arduino needs 5v, relays 12v, dual motor board 21v), 2 cooked arduinos later, and it lives. It looks OK, at least not bad enough to disgrace the turntable. How does it sound? Really good. These dual motors are beauties and the mounting in silicone in the aluminium housing perhaps does a little decoupling. Anyway, I used a high compliance shure with 1.2g tracking force because the record is not exactly damped on the Gale, and it is really smooth and neutral... Have not compared it with the standard turntable yet: that will have to wait until I can get the other one going but I will update the group. The speed is very stable even with load, and is adjusted by a little turning of the potentiometer. No automatic feedback loop and there's not really any need for one...

I hope you can see the video of it going at https://youtu.be/QaDF7pnX5c8 ! 

I was thinking about making a few more, and machining a sub platter so that this could be a drop in replacement without needing any of the old motor & motor controller parts. I know it's not really a Gale any more, but it is a beauty of a turntable, and it goes! And potentially the old motor unit / controller don't need to be sacrificed. I got a price of 200$ for the machining of a faithful copy of the sub platter from stainless, which would be around 40% of the total cost...

Alex




gale pics.001.jpeg
gale pics.002.jpeg
gale pics.003.jpeg

al

unread,
Jul 20, 2020, 6:33:43 PM7/20/20
to Gale Audio
I forgot to say: 

a) is anyone interested in a motor + controller (the motor housing can also be made from the 890mm stainless exhaust pipe I think...

b) the video is terrible! will make a better one....

John Mayberry

unread,
Jul 20, 2020, 7:01:35 PM7/20/20
to gale-...@googlegroups.com

Sounds fascinating.

Since the existing electronics (at least in mine) are going south quickly, I might very much be interested.

Please keep me in mind.

--
You received this message because you are subscribed to the Google Groups "Gale Audio" group.
To unsubscribe from this group and stop receiving emails from it, send an email to gale-audio+...@googlegroups.com.
To view this discussion on the web visit https://groups.google.com/d/msgid/gale-audio/73e199d5-20da-4338-b9b3-0e65b61fe258o%40googlegroups.com.


Virus-free. www.avast.com

Toby Carter

unread,
Jul 21, 2020, 4:43:08 AM7/21/20
to gale-...@googlegroups.com
Thanks Alex,

Great write up, I love to see some ingenuity and redesign when needed to get something working again.
I will find myself a Gale to use myself one day, actually by pure chance I have a Technics SL1200 turn up by courier from Japan today, originally designed as a HiFi turntable it quickly became the choice for DJ’s back in the 1970’s being solid and robust, electronic speed control. They were and still are used by DJ’s so that turntable has been in production pretty much 50 years. Recently Technics revived the brand and the turntable is sold as a HiFi deck, seems to get good reviews. A lot of people are tweaking the original 1200 to make it sound better still for HiFi. Good to see records still very much alive for some while yet.

Toby 



On 21 Jul 2020, at 02:01, John Mayberry <emm...@emmaco.com> wrote:



al

unread,
Jul 21, 2020, 8:12:43 AM7/21/20
to Gale Audio

John Mayberry

unread,
Jul 21, 2020, 1:22:55 PM7/21/20
to gale-...@googlegroups.com

Tell us more about the interface box!

John

 

From: gale-...@googlegroups.com <gale-...@googlegroups.com> On Behalf Of al
Sent: Tuesday, July 21, 2020 5:13 AM
To: Gale Audio <gale-...@googlegroups.com>

--

You received this message because you are subscribed to the Google Groups "Gale Audio" group.
To unsubscribe from this group and stop receiving emails from it, send an email to gale-audio+...@googlegroups.com.

al

unread,
Jul 21, 2020, 4:23:40 PM7/21/20
to Gale Audio
Well, all the arduino does is switch on/off and do a timing to determine RPM. It's not really necessary: you could put the potentiometer and a switch in a box and it would function just the same (you'd just have to fine tune the pitch with a strobe). The EDS500 works with an oscillator and a comparator on the board (I think) so is not dependent on mains frequency (well it works with my 21v DV switch mode supply so it can't be!). It's an impressive motor, used in the dual TTS of the early 70s. The arduino functions are just pretty and make it look a bit gale ish, and give an accurate RPM...

I did a wow and flutter measurement with 'RPM' on my iphone which has a database of turntables tested using the same program, and it measured 0.08% unweighted wow and flutter, which is up with the best (as good as a technics 1210 or a linn lingo LP12). This was a relief! With the more expensive 'w&f' iphone program it measured 0.04% unweighted: excellent! I confirmed that this means something by measuring my cheap rotel belt drive in the same way: 0.4% (and even that is not very audible...). 

If you wanted to do the project in the simplest way, get a) a piece of 89mm stainless exhaust tube (10$) to contain the motor with a rim at the top to 'hang' on the perspex of the Gale (you don't need to machine the aluminium motor housing, it's just that I had one...), a 21v switch mode supply (30$) and some silicone for positioning. It will still perform impeccably. The problem is the sub platter: you have to completely wreck your current motor to get it. The best solution is to machine another from stainless, and that's what I'm going to do. I can definitely do one for you at the same time if you like... The cost of that is much more than the other parts (200$). It will still have the grooves for the rubber rings &c...

Alex

al

unread,
Jul 21, 2020, 4:59:04 PM7/21/20
to Gale Audio
PS the arduino is such a great way to do simple computing. It is easy to program & interface to the world, and the chips cost 5$ to replace if you fry it! Programming them is how all 12y olds should have been spending lockdown!

this is the interrupt routine for timing:

void modifyspeed () {
  newtime=micros();
  rotationtime =newtime-oldtime;
  if (rotationtime > 300000) 
  {RPMint=6000000000/(rotationtime);
  oldtime= newtime;

triggered by the interrupt of digital pin 3 going high -  here is the interrupt instruction:

attachInterrupt(digitalPinToInterrupt(3), modifyspeed, RISING);

and for display & switch:

if (buttonstate==1)
{digitalWrite(relay1pin,1);
digitalWrite(relay2pin,1);
display2.clear();
display.setSegments(blank);
//
}

else {
  digitalWrite(relay1pin,0);
  display2.showNumberDecEx(RPMint,0b01000000, 0,4,0);
  
  if (buttonstate==2)
  {digitalWrite(relay2pin,0);
  display.showNumberDecEx(33,0b00000000,0,4,0);}
  else {
    display.showNumberDecEx(45,0b00000000,0,4,0);
    digitalWrite(relay2pin,1);
  }
}
sensorvalue= Sensor.capacitiveSensor(30);
if  (sensorvalue>sensitivity) {
togglenewtime=micros();
  if ((togglenewtime-toggleoldtime) > 400000) 
  {buttonstate++;
  toggleoldtime= togglenewtime;
  if (buttonstate>3) {
    buttonstate=1;}
  } 
}

of course there are some variables and values here I haven't included, but this is basically the control program...

Alex

On Monday, 20 July 2020 23:22:34 UTC+1, al wrote:

John Mayberry

unread,
Jul 21, 2020, 5:01:01 PM7/21/20
to gale-...@googlegroups.com

Is this something you would want to do (for a an all up price}?

 

From: gale-...@googlegroups.com <gale-...@googlegroups.com> On Behalf Of al
Sent: Tuesday, July 21, 2020 1:24 PM
To: Gale Audio <gale-...@googlegroups.com>
Subject: Re: new motor unit adventures...

 

Well, all the arduino does is switch on/off and do a timing to determine RPM. It's not really necessary: you could put the potentiometer and a switch in a box and it would function just the same (you'd just have to fine tune the pitch with a strobe). The EDS500 works with an oscillator and a comparator on the board (I think) so is not dependent on mains frequency (well it works with my 21v DV switch mode supply so it can't be!). It's an impressive motor, used in the dual TTS of the early 70s. The arduino functions are just pretty and make it look a bit gale ish, and give an accurate RPM...

--

You received this message because you are subscribed to the Google Groups "Gale Audio" group.
To unsubscribe from this group and stop receiving emails from it, send an email to gale-audio+...@googlegroups.com.

al

unread,
Jul 21, 2020, 5:19:38 PM7/21/20
to Gale Audio
Definitely, but it would be best for people with a little know how, who can work a voltmeter, because the whole thing is a little heath robinson on the inside (the looks are deceptive!)... There's quite a high epoxy glue element...

Main costs are motor (I got two for 70$ but it may be necessary to cannibalise a turntable, which is around $200 at the cheapest...) and platter (200$), with everything else around 150$. So worst case is 600$ all in and I'd try to do better... The assembly I am happy to do, but it would be best to do a few at a time, so let's see if anyone else is interested... They would be a good thing to have lying around in case the original motor (inevitably) fries. Or to use everyday and then use the original for showing off!

alex



On Monday, 20 July 2020 23:22:34 UTC+1, al wrote:

John Mayberry

unread,
Jul 21, 2020, 5:24:17 PM7/21/20
to gale-...@googlegroups.com

I would be interested.  My Litton motor is still good if someone wants it afterwards.

John

 

From: gale-...@googlegroups.com <gale-...@googlegroups.com> On Behalf Of al
Sent: Tuesday, July 21, 2020 2:20 PM
To: Gale Audio <gale-...@googlegroups.com>
Subject: Re: new motor unit adventures...

 

Definitely, but it would be best for people with a little know how, who can work a voltmeter, because the whole thing is a little heath robinson on the inside (the looks are deceptive!)... There's quite a high epoxy glue element...

--

You received this message because you are subscribed to the Google Groups "Gale Audio" group.
To unsubscribe from this group and stop receiving emails from it, send an email to gale-audio+...@googlegroups.com.

Toby Carter

unread,
Jul 22, 2020, 2:02:42 AM7/22/20
to gale-...@googlegroups.com
So are the original motors particularly fragile? I would have thought they’d go on for ever given the duty cycle on them is so little only working for perhaps a few hundred hours in a life time with such a little load.
Also given they weren’t a cheap item when they were new in the 70’s, I would have thought they were very robust and well made?

Toby

Sent from my iPhone 7

On 22 Jul 2020, at 00:19, al <alki...@gmail.com> wrote:



SmithMcDougall Family Gmail

unread,
Jul 22, 2020, 3:45:22 AM7/22/20
to gale-...@googlegroups.com
People thought the same about Jaguars and Aston Martins back then too.....
Winking smile
Robin
 
Sent: 22 July, 2020 4:02 PM
Subject: Re: new motor unit adventures...
 
wlEmoticon-winkingsmile[1].png

Pete Wilson

unread,
Jul 22, 2020, 3:49:22 AM7/22/20
to gale-...@googlegroups.com
Stop worrying me!

I have a Jaguar (but much more modern)…..

— P

On Jul 22, 2020, at 9:45 AM, SmithMcDougall Family Gmail <smithmc...@gmail.com> wrote:

People thought the same about Jaguars and Aston Martins back then too.....
<wlEmoticon-winkingsmile[1].png>

Virus-free. www.avast.com

Toby Carter

unread,
Jul 22, 2020, 4:08:26 AM7/22/20
to gale-...@googlegroups.com
I knew there was a reason I have bought BMW’s for years! ;-)
Actually all my earlier life was spent driving Peugeot’s which never let me down.
I think the failing of most brands years ago was the electrics, especially when water was involved! Thankfully manufacturers eventually leant how to waterproof things better, I would say any modern brand is very good in that respect, it just wouldn’t survive nowadays on national pride to own alone.

Toby

Sent from my iPhone 7

On 22 Jul 2020, at 10:49, Pete Wilson <pe...@kivadesigngroupe.com> wrote:

Stop worrying me!

Pete Wilson

unread,
Jul 22, 2020, 4:13:21 AM7/22/20
to gale-...@googlegroups.com
1. Joseph Lucas, Prince of Darkness.

2. Q: Why do the British drink warm beer?
A: Because Joseph Lucas makes refirgerators.

:-)

— P

SmithMcDougall Family Gmail

unread,
Jul 22, 2020, 4:30:39 AM7/22/20
to gale-...@googlegroups.com
Ha!  I had to think about that!  Very droll.  But would probably fly over the head of the North American contingent especially.
Well off-topic I know;  but I’m old enough to remember when ‘Made in Japan’ was an insult.  Then gradually, people became aware that their cars seemed to be heaps more reliable than the local or Euro / USA imports. As far as I read, that’s still pretty much the case.  Koreans a close second apparently?
I also noticed that when Michael Palin did his N-S cross-Africa trip a few years back, he used Toyota Land Cruisers ....
Robin
PS:  The Brit ale isn’t warm.  It just isn’t chilled. Ales especially should be consumed at their temperature of fermentation, and ye old bespoke ale is fermented (typically) at a cellar-type (ie coolish) temp. I’m a long way from the British Isles, but even here in the deep South there’s nothing better than a Theakstons!

Pete Wilson

unread,
Jul 22, 2020, 4:32:40 AM7/22/20
to gale-...@googlegroups.com
I know - but it’s a North American joke, so…
(I’m a Brit, but have lived in USA a lot…)

Toby Carter

unread,
Jul 22, 2020, 4:52:40 AM7/22/20
to gale-...@googlegroups.com
Haha....great to hear some classics.
I’m glad our refrigerators are now fixed, probably Chinese now so much more reliable, most components if not products are manufactured there nowadays.
I’m actually in design and manufacturing in engineering, perhaps got that from my great uncle David Carter (He/DCA developed the GT2101 for Ira Gale), he is still with us, 93 years old.
Anyway I use China a lot for machined components and other parts, I can only speak as I find and the quality nowadays has been incredibly good.

Toby

Sent from my iPhone 

On 22 Jul 2020, at 11:32, Pete Wilson <pe...@kivadesigngroupe.com> wrote:

I know - but it’s a North American joke, so…

al

unread,
Aug 14, 2020, 8:29:41 AM8/14/20
to Gale Audio
Mm. I just used the w/f iphone program to measure the standard Gale's wow and flutter: 0.11%. Pretty good, but my eds500 motor replacement is getting 0.08%! This 'order of magnitude' stuff in the sales may have been a little hyperbolic, as the EDS is early 70s... My impression is that the original Gale motor doesn't actually have a massive amount of torque, which could have something to do with it. 

I am also having a very odd issue with my speed controller: fixed 33 works fine but variable goes full speed into reverse! Does anyone else have a reversing platter?? 

Alex

SmithMcDougall Family Gmail

unread,
Aug 14, 2020, 6:16:28 PM8/14/20
to gale-...@googlegroups.com
I recall reading that the old Sugden (Connoisseur?) turntables were apt to occasionally spin the turntable in the reverse direction.
Which is why they had that odd lever-action ‘on’ switch – to flick the record in the correct direction at start-up.
Robin
 
From: al
Sent: 14 August, 2020 10:29 PM
Subject: Re: new motor unit adventures...
 
Mm. I just used the w/f iphone program to measure the standard Gale's wow and flutter: 0.11%. Pretty good, but my eds500 motor replacement is getting 0.08%! This 'order of magnitude' stuff in the sales may have been a little hyperbolic, as the EDS is early 70s... My impression is that the original Gale motor doesn't actually have a massive amount of torque, which could have something to do with it. 
 
I am also having a very odd issue with my speed controller: fixed 33 works fine but variable goes full speed into reverse! Does anyone else have a reversing platter??
 
Alex

Virus-free. www.avast.com

Mike Nightingale

unread,
Aug 15, 2020, 4:37:17 AM8/15/20
to Gale Audio
I also remember this phenomenon! My friend had a "Connoisseur" deck.
I also vaguely remember being taught the reason that certain designs of electric motor exhibited this behaviour - but can't actually remember the reason! Come to think of it, I can think of a few electrical items where this still occurs, usually though, where the direction of movement doesn't matter, i.e. My Microwave turntable decides randomly what direction to spin, and my deep fat fryer has a similar random direction.

Mike

Toby Carter

unread,
Aug 15, 2020, 5:02:08 AM8/15/20
to gale-...@googlegroups.com
I’ve had it with an engine before, a diesel cement mixer I think!

I’m not sure why certain motors do it......anyway that reminds me I’m now going to play some records! 😁


Sent from my iPhone 7

On 15 Aug 2020, at 09:37, Mike Nightingale <nightin...@gmail.com> wrote:


--
You received this message because you are subscribed to the Google Groups "Gale Audio" group.
To unsubscribe from this group and stop receiving emails from it, send an email to gale-audio+...@googlegroups.com.

Mike Nightingale

unread,
Aug 15, 2020, 5:11:21 AM8/15/20
to Gale Audio
Hmm, after a bit of thought, I think it has to do with two factors 1, Cheapness! It is comparatively easy to "Set" an electric motor's direction of spin, but requires additional components.
2, Lacking these additional components, the direction of spin will depend on the (Random) position that the motor stopped at, essentially where in the complex of magnetic fields it rests deciding which direction it gets "Kicked" in.

Mike

al

unread,
Aug 15, 2020, 5:50:50 AM8/15/20
to Gale Audio
The odd thing is that it goes the right way round for about 1s and then strongly and predictably reverses!

al

unread,
Aug 24, 2020, 3:48:22 PM8/24/20
to Gale Audio
More information: I measured the output wire and the speed of the motor is proportional to the voltage on it. And even a working turntable goes strongly positive at startup and then negative to 'brake' down to 33.3. My reversing motor is due to a continuously negative voltage. This is a board issue - which if you have seen the boards is a little intimidating... Howie's schematics are a wonderful resource but the diagram of the ribbon connector in particular shows various signals going all over the place from board to board! It may be time for an oscilloscope...
Message has been deleted

al

unread,
Sep 20, 2020, 6:56:53 PM9/20/20
to Gale Audio
Well, it turns out that an oscilloscope is an extremely useful tool for the controller. With Howie's schematics you can trace what bit is non functional: in my case the variable frequency generator on board 3. I replaced the IC but that didn't work. So checked the power in and the -10v rail was off. It comes through a resistor, which had failed. Replacing that made everything work!

I also thought everyone might be interested in seeing the wow and flutter trace and the corresponding voltage fluctuation in the drive to the motor, which is surprisingly big (given that 33.3 is coded by 1.2v and 45 by 1.5v: the variation is up to 0.3v!). The optical feedback loop is working hard and I think the motor would be pretty ropey without it... The flutter is typical of a direct drive: what is interesting is the biggest variation x1 per revolution, seen in both the wow/flutter graph and the voltage trace. Can't make it go away however much I clean the disc: must be something mechanical. Figures still excellent though...
IMG_6255.jpg
IMG_6254.jpg

al

unread,
Sep 20, 2020, 7:15:04 PM9/20/20
to Gale Audio
.... and I just realised: the schematics are from Markus, not Howie. They are what got me out of the hole. Thanks Markus!
Reply all
Reply to author
Forward
0 new messages