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Old 30th Mar 2019, 10:22 pm   #1
Michael Maurice
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Default HMV Model 120

I'm restoring this record player which I believe dates from the 1940's. The motor was seized and I freed it off and lubricated the governor mechanism. However after running it for around hour, there was a burning smell coming from the motor.

There are two capacitors either side of the motor which I've removed. They both read O/C on my capacitor meter and are not short circuit, but there are no markings on them. How could I find out what value they may have originally been? I may get the motor rewound though it might have survived the cooking.

Any advice would be most welcome. There is nothing on the net regarding this model.
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Old 31st Mar 2019, 3:29 pm   #2
ms660
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Default Re: HMV Model 120

0.8uF (804...80 plus 4 zeros...800,000pF)?

A later model, HMV 122 shows 2 x 0.7uF in one configuration according to a schematic that's supposed to be for it:

https://nvhrbiblio.nl/schema/HMV_122.pdf

Lawrence.

Last edited by ms660; 31st Mar 2019 at 3:37 pm.
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Old 31st Mar 2019, 6:41 pm   #3
Michael Maurice
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Default Re: HMV Model 120

Thanks for that Lawrence.

one capacitor is marked 804, the other 803. They are in parallel so presume total capacitance is 880nF.

But you can't get motor run capacitors in that low value. The smallest appears to be 1uF.

I dont know if I could use this type of capacitor or do I have to use a motor run capacitor and if so, would a 1uF be ok?
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Old 31st Mar 2019, 6:50 pm   #4
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Default Re: HMV Model 120

I think it's unlikely that '804' means 800nF and '803' means 80nF here, for several reasons :

1) That convention is relatively recent (although the colour code that essentially uses it is much older) and is unlikely to be used in a 1940s motor

2) If the capactors are those values then the smaller is 10% of the larger. I would think the tolerance on said capacitors would be 10% at least, so no real point in adding the smaller one.

3) In any case why not just have one slightly larger capacitor. I could accept that a capacitor of twice the value (say) would not fit conveniently into the available space but I would have thought one of just 10% more could have been designed to fit.

I wonder if the numbers are a part number, serial number, date code or something.
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Old 31st Mar 2019, 6:51 pm   #5
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Default Re: HMV Model 120

Re Post#3, I don't know enough about motors to comment on the capacitor type needed, I expect some on the forum will.

Lawrence.
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Old 31st Mar 2019, 7:13 pm   #6
Michael Maurice
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Default Re: HMV Model 120

Quote:
Originally Posted by TonyDuell View Post
I think it's unlikely that '804' means 800nF and '803' means 80nF here, for several reasons :

1) That convention is relatively recent (although the colour code that essentially uses it is much older) and is unlikely to be used in a 1940s motor

2) If the capactors are those values then the smaller is 10% of the larger. I would think the tolerance on said capacitors would be 10% at least, so no real point in adding the smaller one.

3) In any case why not just have one slightly larger capacitor. I could accept that a capacitor of twice the value (say) would not fit conveniently into the available space but I would have thought one of just 10% more could have been designed to fit.

I wonder if the numbers are a part number, serial number, date code or something.

So how do I find out what the value is?


Of course I could put a 1uF in and see what happens, but don't want to wreck the motor, assuming I haven't already.
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Old 31st Mar 2019, 8:03 pm   #7
Mikey405
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Default Re: HMV Model 120

Hi Michael.

I've recently scanned in the manuals for the EMI K3 deck and the separate "motors" manual and they should hopefully contain all the details you might need.

They can be downloaded from here:

http://www.oldtechnology.net/documen...and_Motors.zip

Thanks Michael.

Kind regards.

From Mike.
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Old 1st Apr 2019, 12:29 pm   #8
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Default Re: HMV Model 120

Thanks to Mikey405, I now have identified the motor as 18670M. The capacitors are 2uF and 1.5uF, new ones have been ordered from RS.

I will test this out tomorrow it would seem that the motor is made for 123V which means the smoke was because it was run from the 200V setting on the transformer. If the motor has burnt out, then I'll get it rewound.

I'll take out the governor again and see it the things runs freely without it otherwise I'll have to remove the motor and completely strip and relubricate it.

Watch this space.
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Old 5th Apr 2019, 10:44 am   #9
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Default Re: HMV Model 120

Its fixed!

I stripped the motor out and relubricated it, cleaned and relubricated the rest of the deck, replaced the capacitors and ran it from the 115V bench supply. No smoke, no burning smells.

One issue that I'm having is that the records do not drop all the way down onto the turntable.

The is a sort of spring mechanism at the side of the spindle, (I'll try and take a picture) which prevents the record from falling to the table, I presume its meant to slow the rate of descent.

Its not operated by anything other than the record itself.

Any ideas.
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Old 5th Apr 2019, 12:08 pm   #10
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Default Re: HMV Model 120

That's an interesting historic museum piece - according to the service data it could be as old as 1934, which would make it one of the world's first autochangers.

A couple of questions/suggestions:

1. The service data suggests that the motor, depending on the model, might be rewirable for 230V. If the motor was set up for 125V, what about the electronics?

2. The spring mechanism on the spindle sounds like the 'antislip' device. Disc slip may well have been a problem with that heavy HMV pickup bearing on the top record. Might be worth trying to disable the spring to allow the record to drop and then checking for slip. Back in those days, I think that 78s were heavier than later post-war records, so might have actuated the device more readily. Otherwise, I can only suggest that the anti-slip device be freed off as much as possible.

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Old 16th Apr 2019, 12:02 am   #11
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Default Re: HMV Model 120

I think Hartley is right, it dropped 12" records with no problems.

Here is a video of it working:

https://www.youtube.com/watch?v=bnTSaYjSJg8
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