rek-o-kut 110v voltage conversion

This is where record cutters raise questions about cutting, and trade wisdom and experiment results. We love Scully, Neumann, Presto, & Rek-O-Kut lathes and Wilcox-Gay Recordios (among others). We are excited by the various modern pro and semi-pro systems, too, in production and development. We use strange, extinct disc-based dictation machines. And other stuff, too.

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Fela Borbone
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Location: Valencia, Spain

Re: rek-o-kut 110v voltage conversion

Post: # 28390Unread post Fela Borbone
Mon Jan 06, 2014 3:52 pm

Hello!
I've had the same problem with my Rek-o-kut. Here (in Spain) is easy to find 220-125 volts transformers in flea markets, so I bougth one and plug the motor thorugh it.Im not an AC motor expert, but I think that a motor build for 60 hz will not work full power at other frequencies (is that rigth?).But, despite the power supply mismatch (125V./50hz to 110V/60hz)it didn't heat up that much for around one hour and a half it was running (connected to the turntable and the overhead). Anyway,In the future I'll bring the voltage down to around 100Volts by removing part of the secondary windings in the transformer,to be more in the safe area. If the motor run slower,it should recive less voltage(may be I'm wrong?).

The speed issue is not that complicated to solve.I fitted a rubber hose at the rotor end (see photo bellow) and just adding a few milimeters diameter it runned faster than required. Next move is trimming the rubber with a blade, checking periodically the RPM (I used a BPM counter) till reach the exact match. The blade should be hold firm, supoortinga it at 90deg to the horizontal to be accurately "lathed"(in the photo the blade is too much tilted)


Image

Image
I'm busy with other projects rigth now, I wish I had more time! Thanks for reading!

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Stevie342000
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Re: rek-o-kut 110v voltage conversion

Post: # 28394Unread post Stevie342000
Mon Jan 06, 2014 4:22 pm

You are part way there you do need to drop the voltage but if you run a 60 Hz motor off a 50 Hz supply it will be running 17% slow.

You should explore this thread and build a frequency controlled motor drive amp.

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Gus
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Location: Athens,Greece

Re: rek-o-kut 110v voltage conversion

Post: # 28400Unread post Gus
Mon Jan 06, 2014 5:58 pm

personally i prefer the electronic solution
such as nigel's frequency controller

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Stevie342000
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Re: rek-o-kut 110v voltage conversion

Post: # 28401Unread post Stevie342000
Mon Jan 06, 2014 6:58 pm

I do as well and with a little thought you could adapt a similar circuit to do automatic Lead in or separation between tracks and lead out groove and locked groove.

There was an automatic lathe controller published in Audio Magazine December 1953 which can be found here: http://americanradiohistory.com/Audio-Magazine.htm

Its a simple design all you need is a trigger to turn the oscillator on and off for a set period of time for each operation. You could use an optical trigger (i.e. remove oxide from tape) or a piece of foil on recording tape (but most of you guys are digital).

Procedure would be:

1 Put blank disc on and clamp it down.
2 connect tape machine to automatic spiralling controller
3 turn on power to equipment
4 Set tape machine to playback
5 turn on suction pump
6 turn on heater and set stylus heating current (you made need to increase the current on inner groove), set meter switch to microgoove or 78, if you have adjustable equalisation set inverse RIAA or what ever curve you wish and set gain controls.
7 Turn on cutting lathe turntable
8 Turn on microscope lamp
9 Lower cutter head to disc and check groove width on test groove
10 cut run in spiral by operating lead in button (a set frequency on oscillator)
11 then set spiralling indicator at separation (which should now be automatic once you've started source)
12 Start tape machine or alternative source (doing it on Audacity you could put the controller frequencies on there at each section for each operation). When you get to last track to be cut you change spiralling indicator to lead out ( if you do it on a computer with audacity you wont need to do this.

Been trying to think of practical ways to implement automatic cutting of lead in - separation and lead out groove for a week or two now.

All you need is an oscillator, a power amp, a step up transformer 15 to 110 or 230v and a motor all as a bolt on unit to turn the crank shaft and lead in screw - a small belt drive should do it on my Sugden or on a Presto 6N. You need to know how many turns of the crank give you lead in - separation - lead out and locked groove. You would then need to work out what frequency would give you the same amount of turns of the crank shaft (lead screw) for each operation and time for the motor to be and the oscillator to be powered up.

With a little more thought you could turn the system into a variable pitch mechanism feed by a signal 1 or so seconds in advance to vary the pitch as music gets louder of softer thus placing cut groove closer together in quiet parts and further apart in loud passages. For example you could have a copy of the track to be cut with the extra sampled frequencies to do lead in, separation and lead out on an alternative track on Audacity and with suitable lead on track to be cut to delay its start from the control track.

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Gus
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Re: rek-o-kut 110v voltage conversion

Post: # 28402Unread post Gus
Mon Jan 06, 2014 7:52 pm

Nice idea! something like David's lathe but without arduino right?

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Stevie342000
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Re: rek-o-kut 110v voltage conversion

Post: # 28410Unread post Stevie342000
Tue Jan 07, 2014 4:42 am

Yes I suppose it is like an Arduino, except as your not moving the whole turntable on a sled. You may need to adapt the idea a bit as you may get the same jerking but probably not as inertia will be lower.

I like the Arduino in concept but have no idea how to program nor any desire to find out, it just makes my head hurt and if my head hurts then it can not be good for me.

I prefer simple that I can understand not based on technology (i.e. solid state) that is only as good as long as the solid state used in that product is in production, 5 to 6 years tops then it becomes obsolete. Nah not for me, this continual so called improvement.

A frequency source, power amp, step up transformer driving a motor which is driving the cutter carriage (lead screw or spiralling crank handle) works just fine for me, I understand it and I can improve it or repair it or learn to leave well alone once it is set up.

Your using the computer in a different way, your using the computer or tape as your source for the material you will cut with additional control tracks for the cutting procedures on Audacity. Sort of using digital but in the analogue domain, if something is logical I get it but 1 & 0 are not logical to me, the way I was taught maths probably (badly) does not help.

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Fela Borbone
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Location: Valencia, Spain

Re: rek-o-kut 110v voltage conversion

Post: # 48531Unread post Fela Borbone
Thu Nov 23, 2017 8:00 am

The pics in my post above are gone, so i shooted another.It still working fine after some years...
The 100v came from a multitap transformer that was very comon in the midle of last century for regulating the power supply in television sets, as voltage from main varyed wildly form differnt locations.
The sleeve is made of plastic pipe, heated to fit, not rubber. Dont know why is less noisy this way.
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Stevie342000
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Re: rek-o-kut 110v voltage conversion

Post: # 48532Unread post Stevie342000
Thu Nov 23, 2017 8:54 am

Capstan sleeves are not the answer either as it will adversely affect wow and flutter which is to be avoided. There are two ways or more of proceeding:
1. the most complex electronic drive - with a variable frequency drive - as covered by Norman Field but he was using it as drive the carriage mechanism/head across the disc.
2. Frequency conversion - change the mains frequency from 50 to 60 hertz or cycles (take your pick) - also not the best option as it produces a square after conversion and not a pure sine wave.
3. Get a new capstan machined in suitable metal - brass is usual if memory serves the difference is speed 17%.

There are formulas that you can use to determine what the diameters of the unknown capstan needs to be taken from the knowns that you have 1. the speed of the motor and the diameter of the drive idler.

It is not that complicated and the simplest method is option 3.

The plastic tubing will deform and cause you the above issue with wow and flutter. If there is less rumble because you are using the plastic sleeve that is because possibly that the drive idler is old and hard and needs to be replaced.

Of course the other way to make sure everything is on speed is if you are using a digital source you speed that up by the X% that the deck is running slow or fast so that on playback it is playing back at the right speed, not sure that works ? Does that work?

Dropping the mains supply voltage is not an issue changing the frequency is.

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Soulbear
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Re: rek-o-kut 110v voltage conversion

Post: # 48538Unread post Soulbear
Thu Nov 23, 2017 4:35 pm

Hi There,
Stevie342000 wrote: Get a new capstan machined in suitable metal - brass is usual if memory serves the difference is speed 17%.

There are formulas that you can use to determine what the diameters of the unknown capstan needs to be taken from the knowns that you have 1. the speed of the motor and the diameter of the drive idler.
The Simple Formulae to do this Calculation are available in 1000+ School and Engineering Books, but even simpler still, I've used this online calculator with great success, in my case, to give me a Capstan Diameter for my Lazarus Lathe Project, when converting the BSR DR33C from its original 78RPM Platter Speed, to a 45RPM Platter Speed. Got it in Nanoseconds and "Bang On" first time, in my case a 12" (12000thou Dead-on) Platter Running at 45RPM, needed a .360" or 360thou Capstan, driven from the Synchronous Motor at 1500RPM. The "Stroboscope does not Lie" Te He!!
BSR DR33C Connoisseur-Disk.3gp
http://www.culvermotor.com/Engineering-Formulas/Pulley-and-RPM-Calculator.html
Easy Peasy Lemon Squeezy
:wink: :P :D Soulbear
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Fela Borbone
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Location: Valencia, Spain

Re: rek-o-kut 110v voltage conversion

Post: # 48539Unread post Fela Borbone
Thu Nov 23, 2017 5:43 pm

Well, the idlers are old indeed...the plastic tubing carved with a blade while spinnng gave not bad results to me.Maybe a metal sleeve can be done the same way. But of course, a proffesional machinist is the best option.

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boryo
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Re: rek-o-kut 110v voltage conversion

Post: # 48543Unread post boryo
Fri Nov 24, 2017 3:04 am

Hi, here is what I found a couple of days ago browsing here.
Sorry I don't have the names of the guys who wrote these replies because I just copy/paste into a file on my computer but here it is:

Reply #1
The age old problem...running 60hz motors in a 50hz country.

No one gave me a straight answer on this. Some said, "get an oscillator and a power amp and a step up transformer"........fuck that.

Here is how you do it and it works because I use it in my studio daily and have no speed or wow issues. Switch on and go.

You need what is called a "Pure Sinewave inverter". These are used in cars/caravans and they convert usually either 12Vdc or 24vDC to AC at either 50 or 60hz depending on which one you buy. Or, what i did was have one custom made which was switchable between 50 or 60hz at 120VAC.

There are two parts to it, the inverter (which converters DC to AC) and the DC power supply (or sometimes known as a "charger").

Things you'll need to check....

Buy accordingly to what frequency output, wattage and output voltage you want.
Make sure the sinewave is good and pure.
Make sure the frequency tollerance is TIGHT.

As most are made not for driving precision equipment or motors, you might want to call a manufacturer and give them your specification and have it custom made, thats what I did. I plugged it in and it worked perfectly. Its just basically generating the mains of the country that you need.

Reply #2
I have done this power conversation to loads of lathes in the UK

12v to 110v inverter, type you get for campers from US eBay

2500 pure sign wave should do.

Then buy a 50amp power supply 12v and just wire it up and off you go.

If you want to go the other way, just reverse the process.

Here is the a link for the first answer, not sure if second was there:
https://www.lathetrolls.com/viewtopic.php?f=4&t=5739&hilit=50hz

Hope this helps,
Bob

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