# I need help to test 2 motors

#### q12x

Joined Sep 25, 2015
1,601
I live in Romania and my profession is artist, and not an electrician. But dont be easily fooled, I do know a lot of general and some quite dedicated electrical details. So.. the story is that my father bought a Very long time ago, like in the 80's, a russian made Magnetophon, an audio device wich worked with 2 Big magnetic tape Wheels. And as a naughty adolescent that I was, around 1998, I dismantle that magnetophon to bits, for my fathers terror. He got over it (I think). Haha. But I kept it's 2 identical motors that are having an unusual working voltage of 70V per motor. Ive always dream of repurpose these motors. So I need your expert opinion about how to make them work.

The yellowish sticker I put it there, with the measured coils: 115ohm and 90ohm (rounded).
So... from my calculations,
I=V/R=70V/90R=0.7A@54W for 1 coil and I=V/R=70V/115R=0.6A@42W for the second coil. And then summed up 0.7A+0.6A=1.3A drawn from the power supply to drive both coils of a single motor.
My problem is... how to actually drive these coils? They are working based of the 50Hz AC? or they need DC? and that will complicate the driver exponentially. Are these universal motors? (running both with AC and DC?) These are questions in my head, but I didnt test anything yet.
From my general knowledge, all the coils in a motor are in series with one another. But these are clearly in parallel, from the measuring. I didnt open the motor yet, and I dont know (if or which ) coil is for the stator or for the rotor. For sure at least one coil is for the stator because I can see the stator is made of a coil, but I can not see the number of them. I should open one and take a look inside to clearly identify what is going on there.
A closeup on the original label:

The soldering metal pad is a single vertical <<bended>> metal sheet, that extends up and down for easy soldering connections. There are only 4 connections, with 4 wires. Not 8.

I have 2 variable power supplies:
Right: the white one is a SMPS(switch mode power supply), with a maximum output of 30V@5A
Left: the Red one is a Variac(variable transformer) for 1 AC phase (not 2 phases) with maximum output of 1000VA or 330V@3A (for a rezistive load)

I acquired the variac a few days ago (from germany via ebay), and one of the many reasons I bought it, was to test my motors I have for literally decades on my shelf. I think a variac is a very good option to have in my arsenal. Ive always wanted one... and now I have it. And is beautiful. Aaah.
Anyway... all this being said, I want your advice how to TEST and RUN these motors, without endanger my equipment or the motors themselves.
Alone... I am a bit unsure and somewhat afraid I will proverbially "fucc" something up. Is better to have an expert eye over my shoulder.
Thank you very much.

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Joined Jul 18, 2013
28,500
On the surface, they appear to be 1ph induction motors, can you see through the end-bell slots and see what the nature of the rotors are, solid or laminated steel with inlaid bars of copper or aluminum etc?

#### q12x

Joined Sep 25, 2015
1,601
I just made a new measure right now and I obtained a short between 2 coils pads:

But only for one single motor.
The other motor is as I described originally and as it is in the yellowish sticker diagram.

#### q12x

Joined Sep 25, 2015
1,601
On the surface, they appear to be 1ph induction motors, can you see through the end-bell slots and see what the nature of the rotors are, solid or laminated steel with inlaid bars of copper or aluminum etc?
No I cant figure out from outside, but the rotor feels extremely fast to spin by hand, suggesting me it has a Very LIGHT rotor. And visually, it looks like a solid block, while surrounded by the stator that appears to have multiple coils disposed as very narrow ovals/O's squished together. This is the best I can see from outside through the gaps. The rotor is painted with a metalic mangenta paint, so I can not get the material that is made from.
Ill have to open it up and actually look inside it, right? I will start doing it now. One moment please.

#### shortbus

Joined Sep 30, 2009
10,044
On the surface, they appear to be 1ph induction motors,
I'd agree by the shape of them, but, a Magnetophon is a reel to reel tape recorder. Wouldn't the motors be something that the RPM can be controlled? To prevent wow and flutter in the recording?

#### q12x

Joined Sep 25, 2015
1,601

Here are some closeups (zoom in with the phone camera as well)
And I scratch with a screwdriver the pink rotor and it appears very scratchable Soft Metal, most probably aluminium solid core rotor.
On the sides you can see the shape of the coil of the stator.
I believe, but im not very sure, at some point, in my (crazy) youth, most probably I may tested at least 1 of these motors directly to 220VAC.... Im not sure about that... that is why I am very curious if something is burned or if everything is fine and working.
I am trying to unscrew the case of one motor, but it has some sort of glue on the screw and is making unscrewing very dificult. Ill update IF I will reach inside it.

#### q12x

Joined Sep 25, 2015
1,601
I'd agree by the shape of them, but, a Magnetophon is a reel to reel tape recorder. Wouldn't the motors be something that the RPM can be controlled? To prevent wow and flutter in the recording?
This is a very close model LOOK (that I quikly find on internet), quite similar with the one I had. Mine was made with wood case and it was like 20 kg heavy and was big like 50 or 70 cm height. It was a vertical model, and "portable" !!! So these were only audio devices, not video. It was the bridge technology between vinyl disks and the very soon to appear audio cassette.

I have only the motors from him, nothing more. Everything else is gone.

Joined Jul 18, 2013
28,500
I would think they should either be synchronous motors or controllable in some way.
They do not appear to be PM rotor.
If PM, shorting the wires together and trying to spin would result in some resistance to spinning.

#### q12x

Joined Sep 25, 2015
1,601
Hoppa - Evika ! I managed (very hard) to open one !
I had to clamp my screw driver in my bench vice and from the other side to unscrew it. Only by hand I had no chance.
Damn, Im good. haha

So...I believe this is the first time I open up this motors.
This is the stator and I have no idea what the windings represents and how they are drive. I know things but to a limit and this is one of those limits.

The rotor:

and the wiring:

You can clearly see the red and the green wire inside.
But the black and the brown wires are not visible from inside, meaning they are under the coils... probably. I didnt want to stress this area too much.

#### q12x

Joined Sep 25, 2015
1,601
I write that I was unsure if it is DC, AC or Universal motor.
I believe it is only AC, if Im reading correct its original label. Is it Right?

SO... how to TEST and possibly drive it? Thats why Im here....

Joined Jul 18, 2013
28,500
They are clearly squirrel cage induction motors, if so, you should be able to run them on AC with the 4uf capacitor value shown on the motor, the capacitor would normally be wired in series with the highest resistance winding, the other direct across an AC source, I agree with @shortbus , they are unusual for reel-reel as some kind of control would be expected.?

#### q12x

Joined Sep 25, 2015
1,601
So... this is what I understand (and what NOT) from your explanation:

Im using the Variac at 20VAC for testing purposes. I did already use it but no kick whatsoever. Maybe these capacitors will have some essential role in it to be drive....??? All I know is capacitors are used to kick-start or jump-start a motor that can not start by itself. It's all I know, about capacitors needed for (some category of) motors. But I also remember those motors were kicking, when I was powering one or more coils, like hickups, but they didnt run unless I helped them spinning by hand their rotor OR by inserting this kick-start capacitor and usually in paralel with the coil. I never used a series capacitor. But Im learning from you now. Very interesting.
Please correct my quick diagram there, I know is not good, but I draw what I could understand from your explanation.
Also, Im not sure if I have such big values for fixed capacitors. For sure Ihave electrolitic capacitors at that value... hmmm.
Thank you so far, mister @MaxHeadRoom !

#### BillB3857

Joined Feb 28, 2009
2,570
Many reel to reel tape units use a dedicated motor to control tape speed and use reel motors that are a 2 phase motor with a weak direction phase to provide only torque to keep the tape from going slack on the take-up side. At least that is how my out-dated reel to reel unit is set up.

#### q12x

Joined Sep 25, 2015
1,601
I've tested (from my variac) with 20VAC and then with 35VAC (which is half of 70) and it should mean half of speed.
And nothing on any pin configuration.

I tested B1 and B2, then C1 and C2. Then
B1 and C1, B1 and C2,
B2 and C1, B2 and C2
C1 and B1, C1 and B2,
C2 and B1, C2 and B2, C2 and C1
Nothing, absolutely no kick in the rotor. and no noise of any kind.
If I remember right, I think they were Extremely silent motors. It passed so much time from then... I might be wrong.
Oh...This is the motor that has interruption between B2 and C1. The one that I opened is having a short between these 2 contacts.

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#### q12x

Joined Sep 25, 2015
1,601
Haha, SHAME on ME that I completely missed this wire, haha. It was bent Under the motor.
So the motor that had a short on the middle pins is this one:

Hahaha. Alright so they supposed to have the middle coils in series as I originally "told it is normal" from my general knowledge.
One mystery solved !

Joined Jul 18, 2013
28,500
Normally if it is a simple AC cap run motor, the low resistance winding will be across the supply, the other winding will have a run capacitor in SERIES with the winding, the two ends, cap and winding end, will also be wired across the supply, if unidirectional, the common neutral point has the end of each winding.
Ignore Centrifugal SW

#### q12x

Joined Sep 25, 2015
1,601
Ok, so my next step was to put a wire on the middle pins, for the one that I didnt open, and soldered on the side pins 2 wires from the AC variac. And I did what you told me, I tested if the rotor was stuck, and it was stuck if I spinned the rotor very-very slowly. But if I spin it fast, it didnt stuck. Very weird but it is interesting that it stuck. So the ENTIRE coils are doing something. This is important to know IF is burned . I really dont know what I did along time.

I pushed up to 60VAC this time and still, no kicking and the rotor stuck like before, maybe a bit more harder but the same, if I rotate it VERY slowly.
I will put a capacitor in series as you say on one of the pins and update you. I hope I have fixed caps that big.

#### vu2nan

Joined Sep 11, 2014
341
Here's the schematic.

It's presumed that B1 - B2 is 91 Ω and C1 - C2 is 116 Ω

Nandu.

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Joined Jul 18, 2013
28,500
Ok, so my next step was to put a wire on the middle pins, for the one that I didnt open, and soldered on the side pins 2 wires from the AC variac. And I did what you told me, I tested if the rotor was stuck, and it was stuck if I spinned the rotor very-very slowly. But if I spin it fast, it didnt stuck. Very weird but it is interesting that it stuck. So the ENTIRE coils are doing something. This is important to know IF is burned . I really dont know what I did along time.

I pushed up to 60VAC this time and still, no kicking and the rotor stuck like before, maybe a bit more harder but the same, if I rotate it VERY slowly.
I will put a capacitor in series as you say on one of the pins and update you. I hope I have fixed caps that big.
You need a capacitor, if had not had one so far. for the motor to start.

#### q12x

Joined Sep 25, 2015
1,601
It is not starting with a capacitor in series.
I found this very big cap of 5.5uF (I believe is a fixed cap).
I tested with a smaller cap (the blue one) rated at 1uF. It didnt work like that either.
Here you can see how I connected everything. I used 35VAC from the variac.

to mister @vu2nan , your link image does Not work.
I get this error from your link: