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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 4th Nov 2017, 1:12 pm   #1
mole42uk
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Default Wearite motor hums

There's a Ferrograph 6 on the bench with a noisy motor. It hums.

I can stop the humming by inserting a screwdriver between the motor laminations and the frame but this isn't an ideal solution. The rubber mounts seem okay, but might not be.

Has anyone any ideas?
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Old 5th Nov 2017, 8:34 pm   #2
BillDWVA
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Default Re: Wearite motor hums

Hi,
Is it a reel motor or the capstan motor that 'hums'?
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Old 6th Nov 2017, 6:41 am   #3
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Default Re: Wearite motor hums

Capstan.
Bearings are good, with no power it rotates silently.
Could be a faulty capacitor I suppose?
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Old 6th Nov 2017, 9:01 am   #4
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Default Re: Wearite motor hums

All AC motors hum, its a question of degree. But as you describe it, stopping VIBRATING when you load the core against the cage, it does sound like a loose lamination stack or cage problem.
Are all the bolts tight?
If it's the lams rattling, get the motor warm, 50C will do, and give it a coat of varnish on the lams. As it cools it will draw it in and tighten the core.
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Old 6th Nov 2017, 10:08 am   #5
mole42uk
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Default Re: Wearite motor hums

This one hums much more than usual for a Ferrograph capstan motor. There's no evidence of loose laminations, the usual amount of varnish is there and the rivets seem tight. All the nuts are tight, first thing I checked!
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Old 6th Nov 2017, 10:35 am   #6
BillDWVA
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Default Re: Wearite motor hums

I suggest checking the phase-shift capacitor for value and leakage. From my experience if it 'loses' capacity then the motor struggles to 'lock' onto speed and may hunt. Maybe you are having another problem with this?
Have the rubber mounts gone too hard?
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Old 6th Nov 2017, 11:00 am   #7
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Default Re: Wearite motor hums

Rubber mounts seem okay, there's flexibility in there which seems as usual.

The Hunts "Therminol" capacitor reads 0.83F for a stated capacity of 0.75F 10%, ESR reads 1.1Ω and Vloss is 0.2%.
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Old 6th Nov 2017, 9:12 pm   #8
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Default Re: Wearite motor hums

If its reading high in value, even just in the 10%, it is possible leaky. Are you using a bridge or a Chinese magic tester?
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Old 7th Nov 2017, 6:43 am   #9
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Default Re: Wearite motor hums

A quick check with the Chinese tester, my Heathkit bridge is not in that workshop.

Leaving the capacitor out of circuit reduces the hum a lot, so I’ll dig in the box of spares today and find something suitable.
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Old 10th Nov 2017, 6:41 pm   #10
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Default Re: Wearite motor hums

Your first comment refers to the action of the screw driver which in essence is acting as a wedge. I used to work for GEC M/Cs (many moon's ago) and the fitter's were forever making wedges and hammering them in to stop the associated problems.
I would do this using home made wedges out of wood or plastic and then varnish as per Boater Sam recommendations.
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Old 11th Nov 2017, 8:19 pm   #11
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Default Re: Wearite motor hums

Mention above of loose laminations, but that would more likely cause a buzz than hum.

One - albeit unlikely - thought: could this by any chance be a 110 volt motor fitted where a 240V one should be? This is only a possibility if the deck has never been run for more than a few minutes, otherwise the motor would cook and burn out!
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Old 12th Nov 2017, 9:41 am   #12
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Default Re: Wearite motor hums

I have some replacement rubber motor mounts and a replacement capacitor on order. One or both may fix the problem.
There’s no evidence that the motor is 110v or of loose laminations.
Further news to follow.
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Old 13th Nov 2017, 12:17 pm   #13
Vintage Engr
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Default Re: Wearite motor hums

Your mention of rubber mounts reminds me that I need to order some for one of my Ferrographs.
I found something similar, but not really an exact replacement. It would be good to know where you are obtaining them from.

Thanks,

David.
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Old 13th Nov 2017, 6:52 pm   #14
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Default Re: Wearite motor hums

Quote:
Originally Posted by mole42uk View Post
I have some replacement rubber motor mounts and a replacement capacitor on order. One or both may fix the problem.
There’s no evidence that the motor is 110v or of loose laminations.
My reference to wedges given previously was not particularly associated with loose laminations but more the problems arising out stray eddy currents that often occur within motors and transformers.
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Old 14th Nov 2017, 10:43 am   #15
mole42uk
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Default Re: Wearite motor hums

Quote:
Originally Posted by Vintage Engr View Post
Your mention of rubber mounts reminds me that I need to order some for one of my Ferrographs.
I found something similar, but not really an exact replacement. It would be good to know where you are obtaining them from.
Mine came from Terry at Ferrographworld.com, he's on this forum too as terry123.
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