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Old 20th Jan 2022, 11:18 pm   #1
vinrads
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Default HMV pickup rewound coil.

I have just rewound the coil on this HMV pickup ,I ended up with about 2.9k ohm , would this be about right ? I managed to find a piece of silicone tube to replace the original which had gone hard , not sure about the square pad it seems quite soft ,I will be trying it in the morning . Mick.
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Old 20th Jan 2022, 11:29 pm   #2
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Default Re: HMV pickup rewound coil.

Well done ! It looks very nice.
As a matter of interest, what gauge of copper wire did you use ? The thinnest enamelled copper wire I have been able to get is "40 SWG".
Did you do it on a coil winding machine or hand wind it ? Which ever it was, you have done a very neat job of it !
I look forward to hearing about the results you have obtained from, it when you try it out on a record.
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Old 21st Jan 2022, 10:06 am   #3
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Default Re: HMV pickup rewound coil.

Thanks for that , the wire is 0.05mm I used an old drill motor and the forward/ reverse/speed ass fitted into a box for easy operation ,as for now I have to guide the wire by hand .Mick
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Old 21st Jan 2022, 10:10 am   #4
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Default Re: HMV pickup rewound coil.

For some reason those pads on HMV pickups seem to survive well, unlike Garrard ones. At one point they used a flattened bit of rubber pipe which went under the plate then over the little sticking up bit on the armature. That goes solid.

How did you manage to rewind it? Patience and good eyesight? Edit - just seen your previous post. Very impressive setup!
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Old 21st Jan 2022, 10:28 am   #5
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Default Re: HMV pickup rewound coil.

Just a thought , am I correct in saying that magnets loose some magnetism over time , my thoughts were to try fitting Neodymium magnets, thought please! Mick.
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Old 21st Jan 2022, 10:32 am   #6
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Default Re: HMV pickup rewound coil.

I have rewound a few of these. 2.9K sounds good and should give plenty of output. The needle armature can be damped with silicon rubber sleeving, the more supple the better.

I used a two speed battery drill, a Black and Decker that would run at one revolution a second. Like yours I used my fingers as tension on the fine wire. The last effort was the 1935 GEC radiogram I posted a while back. Regards, John.
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Old 21st Jan 2022, 9:12 pm   #7
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Default Re: HMV pickup rewound coil.

After fitting the pickup and a makeshift counter balance weight , it works fine ,loads of volume ,now looking for a counter balance weight ,if I have to make one an idea of the weight would be useful , also I need to find some paint to match , thanks Mick.
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Old 21st Jan 2022, 9:56 pm   #8
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Default Re: HMV pickup rewound coil.

Hi Mick resistance seems about right and although some of these coils used 0.025mm wire I have found that 0.063 gives sufficient turns for good volume.
Small modern magnets may help; wire obtainable in 100g reels from Scientific Wire Co

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Old 22nd Jan 2022, 12:31 pm   #9
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Default Re: HMV pickup rewound coil.

I think this is the type of counterbalance weight needed.
It weighs a good old fashioned 7ozs on the balance scale that is probably a lot older than the pick-up! John.
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Old 22nd Jan 2022, 12:39 pm   #10
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Default Re: HMV pickup rewound coil.

Extra pic added.
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Old 22nd Jan 2022, 1:19 pm   #11
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Default Re: HMV pickup rewound coil.

Good work!

Anything below 0.06mm I regard as 'trouble' needing care, even pulling it off the reel.

Though it helps to be winding on a circular former - a rectangular one gives rise to cyclic jerks, four per revolution, as the wire passes round each corner, needing a low-inertia tensioning system.
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Old 22nd Jan 2022, 1:51 pm   #12
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Default Re: HMV pickup rewound coil.

Quote:
Originally Posted by vinrads View Post
Just a thought , am I correct in saying that magnets loose some magnetism over time , my thoughts were to try fitting Neodymium magnets, thought please! Mick.
Magnets do, over time, loose a bit of their magnetism.... But as you say you have lots of output, I would guess that there is sufficient magnetism still left.
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Old 22nd Jan 2022, 2:08 pm   #13
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Default Re: HMV pickup rewound coil.

Quote:
even pulling it off the reel.
That is why you pull it over an end, the ends are smooth just for that reason.
 
Old 22nd Jan 2022, 5:20 pm   #14
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Default Re: HMV pickup rewound coil.

Quote:
Originally Posted by Heatercathodeshort View Post
I think this is the type of counterbalance weight needed.
It weighs a good old fashioned 7ozs on the balance scale that is probably a lot older than the pick-up! John.
Thanks John that's a great help , if if I don't find an original I will have to have one turned ,love the scales . Mick.
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Old 23rd Jan 2022, 12:28 pm   #15
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Default Re: HMV pickup rewound coil.

Green Grocer's scales. Very accurate as they have to comply with weights and measures.
If it's going to be a drama and costly getting that weight fabricated, let me know and I will see if I can find you one. Loads of old pick-ups in the garage loft...It's cold outside.. John.
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Old 23rd Jan 2022, 6:17 pm   #16
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Default Re: HMV pickup rewound coil.

Thanks John PM sent Mick
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