Mechanical video recorder

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Re: Mechanical video recorder

Postby Steve Anderson » Sat Dec 07, 2019 5:28 pm

A good old-fashioned 'record player' that is mains powered will probably use a synchronous motor - I think called 'shaded pole', but I'm not certain. But better (expensive) and more recent 'Hi-Fi' turntables will often use a direct-drive motor which requires quite a bit of support electronics. They are generally low-voltage too.

You'd be looking for a donor record player (or a radiogram) from the 50s/early 60s probably. If you're lucky it'll also have a transformer for the the tube/valve amplifier, useful for CRT stuff...

Steve A.

Also, and I hate to say this, tape recorders...

...a trip to the local dump/tip/recycling place may be in order...

Be careful, if they've sat unused (probably) for many years check if you can turn the motor spindle to see if it's free and not seized. If it is get some penetrating oil, apply to the bearings every few days - gently try and turn the rotor with your fingers, if it doesn't move - more oil, more time...do not use pliers, mole-grips or any form of tool to move it...I've brought quite a few back to life this way....patience is the by-word, it can take weeks to free up...warmth (but not too much) helps, not really Melbourne's strong point!
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Re: Mechanical video recorder

Postby Steve Anderson » Sat Dec 07, 2019 6:06 pm

Photo shows a synchronous motor revived in a UK made tape recorder from the early 60s. Generally they'll look similar. Also note the power transformer for the valves/tubes and the smaller audio output transformer.

Some may only have a single winding, mainly record players as the motors don't need the power or torque for fast-spooling the tape.

Steve A. (Somewhat of a tape-head).

The photo reminds me of open-heart surgery!
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Re: Mechanical video recorder

Postby Harry Dalek » Sat Dec 07, 2019 8:54 pm

Steve Anderson wrote:A good old-fashioned 'record player' that is mains powered will probably use a synchronous motor - I think called 'shaded pole', but I'm not certain. But better (expensive) and more recent 'Hi-Fi' turntables will often use a direct-drive motor which requires quite a bit of support electronics. They are generally low-voltage too.


I do have 3 handy ones a 50s other a 70s but 110v i think,..... never used it not well made a kids record player the other a converted wind up mechanical player some one in the 50s converted to a mains player destroying it really !,,,but it has the motor as well .

You'd be looking for a donor record player (or a radiogram) from the 50s/early 60s probably. If you're lucky it'll also have a transformer for the the tube/valve amplifier, useful for CRT stuff...


My scrapping mind already was ahead of you Steve :wink: a few months back i opened it up to look one valve amplifier and no transformer direct to deadly mains power ! ...i was not going to fiddle with it ..but worth scrapping for the motor ..just till now i had no need .

Steve A.ir

Also, and I hate to say this, tape recorders...


i have two reel to reel but will not destroy them BTW i recall scrapping some Beta VCRs the video head motor were AC bit big but !

...a trip to the local dump/tip/recycling place may be in order...


My shed is well stocked ! funny enough i don't recall to many record players about ....ALDI were just selling new turn tables for 99 bucks so newer ones are still here and there .

Be careful, if they've sat unused (probably) for many years check if you can turn the motor spindle to see if it's free and not seized. If it is get some penetrating oil, apply to the bearings every few days - gently try and turn the rotor with your fingers, if it doesn't move - more oil, more time...do not use pliers, mole-grips or any form of tool to move it...I've brought quite a few back to life this way....patience is the by-word, it can take weeks to free up...warmth (but not too much) helps, not really Melbourne's strong point!


Very true ! the ones i have all work apart from the kids one but never powered it up may be i should just start again and convert one instead the motors are to big for the one i have been working on ,the converted mechanical from the 1920s or before would be the one worth trying more so for the case ! give it some use and at least fix the mess that fool made to it all the years back drilling holes every where ! but all i would like to see how true the platter rotates flat no good if i have seen wobble its bad enough when every thing looks flat for recording .
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Last edited by Harry Dalek on Sat Dec 07, 2019 9:31 pm, edited 4 times in total.
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Re: Mechanical video recorder

Postby Harry Dalek » Sat Dec 07, 2019 9:18 pm

Steve Anderson wrote:Photo shows a synchronous motor revived in a UK made tape recorder from the early 60s. Generally they'll look similar. Also note the power transformer for the valves/tubes and the smaller audio output transformer.


Ok when i get a chance i will show my old gear see if the motors are similar ,the from the time 50s player i rather for one reason case is very crappy ! but it also does 16 RPM only one i have ever seen

Any case as long as it has 78 RPM ....which records SSTV well at least

Some may only have a single winding, mainly record players as the motors don't need the power or torque for fast-spooling the tape.


I tried a microwave fan motor as well as the turntable motor as i think it as well is synchronous but had little torque so didn't like that one much
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Steve A. (Somewhat of a tape-head).
The photo reminds me of open-heart surgery!


I suppose your right Doctor Steve 8) it is a bit like that opening things up i mostly do postmortems my self :shock:
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Re: Mechanical video recorder

Postby Viewmaster » Sat Dec 07, 2019 10:17 pm

You have so many CD's Harry that you will need an auto changer
like this 78 RPM job.
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Re: Mechanical video recorder

Postby Klaas Robers » Sat Dec 07, 2019 11:31 pm

These motors are weak motors, if you need a higher speed, say 1 rps, 60 rpm. But from the film I realized why the turn table in our microwave runs sometimes to the right and sometimes to the left. The problem with simple synchronous motors is that they don't start. I had once an electric clock that did not start, and you had to give it a swing before it ran. You might know this from an old bike dynamo. You can use it as a motor on 50 Hz (then it runs on 12,5 rps!) but it should be started by hand, or by a small DC-motor. We used bike dynamos as motor for running a Nipkow disc.

The motor of the microwave had a provision that it will start, but you don't know which direction. That depends from the moment that you switched it on, the phase of the AC at that very moment. Learnt something.......

I got two Philips synchronous motors, that run on 230 volt, with a capacitor, 250 rpm. One has a universal gearbox screwed on, that you can configurate for quite some output speeds. I have all documentation of them. If you want to have it..... Should I ship it to Australia?
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Re: Mechanical video recorder

Postby Harry Dalek » Sun Dec 08, 2019 8:22 am

Viewmaster wrote:You have so many CD's Harry that you will need an auto changer
like this 78 RPM job.
78 record changer.jpg


Yes pretty much have more than enough for this project those were all the mistakes on the old player from experimenting .

I like 78 rpm it got me an image !....I am rebooting the project that case will be used then insides motor rubber is worn out a bit and platter is noisy so will use another i have found .
i will post up later today some photos ...
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Re: Mechanical video recorder

Postby Harry Dalek » Sun Dec 08, 2019 8:35 am

Klaas Robers wrote:These motors are weak motors, if you need a higher speed, say 1 rps, 60 rpm. But from the film I realized why the turn table in our microwave runs sometimes to the right and sometimes to the left. The problem with simple synchronous motors is that they don't start. I had once an electric clock that did not start, and you had to give it a swing before it ran. You might know this from an old bike dynamo. You can use it as a motor on 50 Hz (then it runs on 12,5 rps!) but it should be started by hand, or by a small DC-motor. We used bike dynamos as motor for running a Nipkow disc.

The motor of the microwave had a provision that it will start, but you don't know which direction. That depends from the moment that you switched it on, the phase of the AC at that very moment. Learnt something.......

I got two Philips synchronous motors, that run on 230 volt, with a capacitor, 250 rpm. One has a universal gearbox screwed on, that you can configurate for quite some output speeds. I have all documentation of them. If you want to have it..... Should I ship it to Australia?



No thats ok Klass i have some spare players i will adjust to reboot to my needs in this project and use 2 to make one i will post up the photos later .

Yes i notice the reverse effect of start up on the 5 rpm motor would not be to bad on a mechanical drum for say sstv but yes i was just thinking about this yesterday !

I have a old bike dynamo... have to try that one day !

So at the moment Klaas looking into the record player the motor in the mechanism looks like that fan motor seems to have enough torque for the lathe part can go down to 16 rpm but i am interested in 78 rpm which is its top speed and it seems to work well for a 70 year old player quiet enough platter is flat spinning this might just do ...i just have to get it to fit its new case .

I will explain in photos later to day .

Stuck with mains frequency speed but i was meaning to ask can you use an oscillator and amp to drive the motor to adjust it to higher speed ? or just correct any wear to the rubber or belts driving the platter speed ...?
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Lets start again

Postby Harry Dalek » Sun Dec 08, 2019 6:49 pm

Wanting to try a synchronous motor and due to their size to my current project i may as well just convert a turntable plus hope this time turn table is speed stable .

So had a look at what i had handy as mentioned before had a children's 70s player but its only got 33 RPM so didn't bother with that as i wanted the turntable and motor that can do 78 Rpm...so that for this its not useful to me .

Next i had a very early hand cranked player some one had gutted and tuned into a motor driven player perhaps in the 50s only thing original is the case and the platter.

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It plays very ruff and scraps the case as it turns also the rubber is warn to much only does one speed no matter what you adjust it to .

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If the mechanism was good i might of just went with this as is as i like the case

Next i had a player where the mechanism was good but the case was a mess

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Now i worked on turning 2 players into one next post .....
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Re: Mechanical video recorder

Postby Harry Dalek » Sun Dec 08, 2019 7:09 pm

I would added this to the last post but starting to get a bit long with the photos ..

Now i needed to fit this turntable in this case ! well that was the plan

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I was thinking of just cutting the turntabe to size but the plywood was in a bad state to many holes under the ugly covering sorry 1950's!

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Well after some cutting a plank and remounting it all again the player fits in this case ,i will see how high or low i want this in the case as i am doing all this all opposite to the first go did the lathe part first .

I suppose i will have to work out where to place some controls again and how i will do the lathe part ,hope its a touch easier this time around knowing what works .
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Re: Mechanical video recorder

Postby Klaas Robers » Sun Dec 08, 2019 10:27 pm

The record player motors and the motors in tape recorders are almost always so called "asynchronous motors". They try to keep up with the mains frequency, but they always run slightly slower. This lower speed gives them the torque, the more torque you need, the slower they run. The advantage is that they start very reliable from a speed of zero (high torque).

The old 78 rpm players needed a really high torque in the beginning, when playing at the outerside of the disc. They had realy large motors. Later the players were optimized for 33,3 rpm and 45 rpm, while the weight of the pick-up head was much lower, so a much lower torque was asked for and smaller motors could do the job. For 78 rpm, with a much lighter pick-up, the motor was just powerfull enough.
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Re: Mechanical video recorder

Postby Harry Dalek » Mon Dec 09, 2019 5:11 pm

Klaas Robers wrote:The record player motors and the motors in tape recorders are almost always so called "asynchronous motors". They try to keep up with the mains frequency, but they always run slightly slower. This lower speed gives them the torque, the more torque you need, the slower they run. The advantage is that they start very reliable from a speed of zero (high torque).


So the gearing size's on the spindle and rubber idler wheel size i would think were designed for the correct rpm speed for the platter using this type of motor ? must work or they would not of bothered with this type of motor speculating :wink: .

The wear over the years must cause the speed to go off how far off i am don't know yet what i do want if it is off just to stay at a constant speed any case can't worse than the DC motor i was trying

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The old 78 rpm players needed a really high torque in the beginning, when playing at the outerside of the disc. They had realy large motors. Later the players were optimized for 33,3 rpm and 45 rpm, while the weight of the pick-up head was much lower, so a much lower torque was asked for and smaller motors could do the job. For 78 rpm, with a much lighter pick-up, the motor was just powerful enough.


Oh that's interesting the one in this is not all that powerful as in the schematic above but seems to have a enough torque the rubber idler still seem's ok i have seen these motors in fans and the fans in micro wave ovens ...i didn't know about asynchronous motors .

I see they have used magnet eddy current brakes for speed control on players but i would of though you would need a increase more for these motors when things wear out and drop RPM....but as i said before i am more interested here in steady constant speed.


youtu.be/-BW7rM84zcA
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Re: Mechanical video recorder

Postby Klaas Robers » Tue Dec 10, 2019 8:42 pm

Wear on the "idler" wheel does not change the speed. The speed at the inner side of the platter is equal to the speed of the outer side of the motor. And as the metal parts are not wearing out, the speed will not change. Only when the rubber wheel wears to unround, you get speed changes.

The type of motor that you described, the shaded pole motor, gives torque on the slip (small reduction in speed) of the motor. That is the reason that with some braking force (edy current), you can change the speed somewhat. This is contrary to a synchronous motor, which runs exactly the speed of the mains, or it stalls. The difference is the rotor: for a synchronous motor it is a strong magnet, for a asynchronous motor it is a cylinder of iron with a copper structure in it.

If you want to fine tune the speed of a synchronous motor, the only way is to change the frequency of the powering voltage. I did that for a mechanical clock that was designed for 60 Hz, which I could only make with the aid of a quartz crystal, divider and a power amp.

Speed control for the asynchronous motor, you know.
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Re: Mechanical video recorder

Postby Steve Anderson » Tue Dec 10, 2019 10:35 pm

Klaas Robers wrote:...I did that for a mechanical clock that was designed for 60 Hz, which I could only make with the aid of a quartz crystal, divider and a power amp.

A novel way I have seen of generating 60Hz from 50Hz for a clock of just a few watts, is to full-wave rectify the 50Hz so that it's now 100Hz with no filtering (capacitors). Then using a bandpass filter extract the third harmonic (300Hz), square it up, divide by five (74xx90) = 60Hz. Filter that to a sine wave...small power amplifier, transformer and you're done. It sounds complex but it's actually not.

I would link to the website but t's down at the moment.

This would only work in countries where the long-term power frequency is kept in check, say Australia and the UK, others too probably. But I very much doubt here!

The alternative is GPS, even that's not so difficult...

Steve A.

Seems the site is up...for how long?....Also it's the 600Hz harmonic that's extracted, divided by 10, and so on...

https://sound-au.com/clocks/freq-changer.html

Actually the author doesn't use a transformer, he rewinds the clock motor for 12V operation...no reason why you couldn't use a transformer, saves rewinding the clock motor...

The author is concerned with safety issues, old electric clocks with old insulation etc...so he's erring on the safe side...plus you don't need that transformer...

Later on he does show how to use a transformer - with a warning that the output is just as dangerous as the 'real mains'...
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Re: Mechanical video recorder

Postby Harry Dalek » Wed Dec 11, 2019 4:43 pm

Klaas Robers wrote:Wear on the "idler" wheel does not change the speed. The speed at the inner side of the platter is equal to the speed of the outer side of the motor. And as the metal parts are not wearing out, the speed will not change. Only when the rubber wheel wears to unround, you get speed changes.


Well that's a good thing ,i was worried what ever wear it had over the years this might effect it but mines still seems very round unlike the one i rejected it has a big indent init .


The type of motor that you described, the shaded pole motor, gives torque on the slip (small reduction in speed) of the motor. That is the reason that with some braking force (edy current), you can change the speed somewhat. This is contrary to a synchronous motor, which runs exactly the speed of the mains, or it stalls. The difference is the rotor: for a synchronous motor it is a strong magnet, for a asynchronous motor it is a cylinder of iron with a copper structure in it.



OH i see ...well i hope if it is touch off its designed RPM what ever it is just stays constant .

I was working on what i hope to be the new dual lathe and player a new design for the lathe arm which i hope to also use as the play arm ,i can disengage the geared motor for the player arm so it would work as normal .

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If i have any problems i will go with this idea from a vintage lathe one arm for the player and other recorder ,just seeing what i can laying around and see it it comes in useful knocking this together ,once i have the lathe arm working i will be very happy .

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If you want to fine tune the speed of a synchronous motor, the only way is to change the frequency of the powering voltage. I did that for a mechanical clock that was designed for 60 Hz, which I could only make with the aid of a quartz crystal, divider and a power amp.

Speed control for the asynchronous motor, you know.


Well around 78 rpm should be ok for my experiments at the moment i will be please if it works as hoped .

My thoughts below on the record head :roll:
I have been thinking of a new recording head for this looking at the old crystal head information below its range is lower than my converted stepper .. mine go's up to 8khz ,i have been thinking of using a current play back ceramic play back head in reverse as it's range is wide and what's wanted at least 10khz , i would think it would have the same range in feeding it .
I have seen the idea of feeding a ceramic head via a small amp and it does work it would need a fair few watts to vibrate it enough
If it doesn't work out its a no goer i will have to go magnetic again and see if i can make some thing better than the one i have now .
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