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Vintage Tape (Audio), Cassette, Wire and Magnetic Disc Recorders and Players Open-reel tape recorders, cassette recorders, 8-track players etc.

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Old 16th Sep 2018, 7:27 am   #1
jascha
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Default Valve tape recorder AC motor question

Hi everyone,

I have been carrying out a few routine repairs on a Japanese tape recorder (Lucor 561B) changing leaky caps etc however I still have an issue with the motor. Firstly, the AC motor is drawing around 0.6A at 117v operation and the rest of the circuit around (0.4A). I suspect it’s on the high side, that for a 70W rated appliance the current measured is around 1A?

Secondly, the machine is running under speed. I have taken the motor apart, cleaned it, relubricated it and all back in operation, however it’s runnijg slower than it should. Sounds like the capstan is missing the 60-50hz sleeve but the sleeve is in position. The motor has a label on it that says 100v 50-60hz.
I can machine a new capstan sleeve to make up the difference however it defeats the issue here as to why it’s running at a slightly lower speed on both 3 3/4 & 7 1/2 ips and why it consumes 0.6A of current on its own. Sounds like it’s still running set at 60Hz but on a 50Hz UK supply. I’m confused!
Any help is much appreciated please.

Thanks
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Old 16th Sep 2018, 7:34 am   #2
barrymagrec
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Default Re: Valve tape recorder AC motor question

High current and slow could be shorted turns on the motor.
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Old 16th Sep 2018, 7:35 am   #3
Ted Kendall
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Default Re: Valve tape recorder AC motor question

If there is a motor run capacitor, check its condition and value, which will be different for 50 and 60 Hz supplies.
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Old 16th Sep 2018, 7:36 am   #4
jascha
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Default Re: Valve tape recorder AC motor question

I thought so too. Where can I find a suitable replacement? Do they all turn at the same speed? A challenge I guess lies ahead!
There is no motor run capacitor I’m afraid on this one.
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Old 16th Sep 2018, 8:11 am   #5
jascha
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Default Re: Valve tape recorder AC motor question

I suspect that this machine does not need a capstan sleeve after All! I am in doubt at this point. There is a bronze sleeve already on the shaft and the machine came from the USA and is a 117v model. Could it be that it was originally used in the USA with the sleeve in place so there is no wear and tear on the capstan shaft? I just wonder! If that’s the case then the machine needs a different sleeve (which I can make for it). However is a current consumption of 0.6A normal for an AC synchronous motor?
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Old 16th Sep 2018, 8:27 am   #6
barrymagrec
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Default Re: Valve tape recorder AC motor question

The consumption seems quite high even though the motor has a fan - does it get very hot?

Bear in mind that the motor will take more current at 50Hz than at 60Hz.

There is no guarantee that the motor is synchronous, most probably not in fact - if it was it would not run slow, just stall if it was overloaded.
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Old 16th Sep 2018, 8:37 am   #7
jascha
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Default Re: Valve tape recorder AC motor question

I have not let it run enough to see if it gets too hot. I shall check. All I can say is that even after relubrication it seems not to run too freely when giving it a spin. It tends to stop after a few turns. The sinteered bearings on either side seem quite stiff to move about. Maybe these are factors that contribute to the consumption if there’s resistance? I still believe that this model how ver needs a 50Hz sleeve made for it as otherwise why would it have a sleeve already on the capstan shaft for just 60Hz operation where it originally resided and was intended to be used? The thickness of the sleeve is a giveaway as it seems quite thick compared to another machine I have that has also a capstan sleeve but was built to be used internationally (has a voltage selector 110-240v). The machine in question has no voltage selector but has a thick capstan sleeve (thicker than needed for 50-60Hz compensation).
Thanks again.
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Old 16th Sep 2018, 8:47 am   #8
wd40addict
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Default Re: Valve tape recorder AC motor question

Was speed OK before you disassembled? As it sounds like the motor is now stiff have you used too thick an oil to lubricate it, or have the bearings failed to fully self-align?

Loads more on this subject here:

https://www.vintage-radio.net/forum/...d.php?t=148519
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Old 16th Sep 2018, 10:24 am   #9
jascha
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Default Re: Valve tape recorder AC motor question

The speed was always under since it came to the Uk. The lubricant and grease used is specially designed for these types of motors and have used them on other motors. I think the bearings are too stiff to align themselves maybe?
I am thinking of trying out the motor just instantly without the rotor to see what current readings I get, so I can eliminate a few suspicions.

Thanks
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Old 16th Sep 2018, 11:38 am   #10
Michael Maurice
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Default Re: Valve tape recorder AC motor question

This motor is designed to run on 60Hz. In the UK we use 50Hz mains so the motor will run slow.

The motor bushes have in all probability failed to align, what I normally do is before tightening up the screws, I give the bearing housing a whack with a screwdriver handle, seeing that the shaft turns freely, then carefully tightening up the screws.
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Old 16th Sep 2018, 11:47 am   #11
jascha
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Default Re: Valve tape recorder AC motor question

I attach a few pictures to show. I have just freed the motor and relubricated it, current is still high however. On the label of the motor it says 100v 50-60Hz. I am using a variac and thatís how I know the current measurements.
Thanks again
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Old 16th Sep 2018, 11:54 am   #12
jascha
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Default Re: Valve tape recorder AC motor question

Here are pictures of the capstan sleeve. This to me looks too thick to be a sleeve for 60-50Hz conversion. I compared it to other sleeves I have for different machines. They are much thinner.
I think therefore this is not a sleeve for speed adjustment but for protection against wear on the capstan shaft itself

Thanks
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Old 16th Sep 2018, 12:04 pm   #13
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Default Re: Valve tape recorder AC motor question

You could try working out the required capstan diameter by assuming 1400 rpm for the motor and measuring the pulley and flywheel diameters.
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Old 16th Sep 2018, 12:08 pm   #14
jascha
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Default Re: Valve tape recorder AC motor question

It’s an easy calculation:
Diameter 60Hz measured 6.994mm. For 50Hz it works out at 8.393mm outside diameter. Just a simple straightforward calculation. I made the calculation based on another sleeve I have and the maths worked out well.
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Old 16th Sep 2018, 3:12 pm   #15
merlinmaxwell
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Default Re: Valve tape recorder AC motor question

With AC, current times voltage doesn't always give power, only VA (volts/amps) it is all to do with the phase shift of the current vs. the voltage.
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Old 20th Sep 2018, 5:58 pm   #16
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Default Re: Valve tape recorder AC motor question

Japanese motors of this era (think Akai) used to develop shorting turns which might be your problem. Could someone have tried this machine on 240V by mistake before you got it?
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