Help with Hadcock 228 tonearm counter weight - diyAudio
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Old 20th October 2006, 05:41 AM   #1
fergs1 is offline fergs1  Australia
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Default Help with hadcock 228 tonearm counter weight

Greetings ladies and gentlemen, I'm in need of help. I have a hadcock 228 tonearm I aqquired on Ebay and the counter weight is too heavy for my cartridge. the counterweight originally came with I believe four different weight sleeves that were slipped over the counterweight and secured with a setscrew to manage all cartridge possibilities.
Mine came with two but both are still way too heavy for my ortofon om30 super cartridge. I can't even get the tonearm vertical then alone forward and I just dont want to add weight to the headshell as I'm told that this will affect the resonance of the tonearm.
Would anyone have any of the lighter sleeves kicking about and would be willing to sell to me as I've been without my vinyl for 3 mnths and its starting to really bug me as Ive also done a lot of opp shoppoing in that time and have a back catologue of about 100 records I still haven't been able to listen to.Any help would be greatly appreciated

cheers fergs
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Old 20th October 2006, 10:29 AM   #2
EC8010 is offline EC8010  United Kingdom
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Actually, you might want to add mass to the cartridge. The OM30 without the little brass insert is very light and the Hadcock has a very low effective mass. The frequency of the fundamental mechanical resonance might be rather higher than is required. I assume you're saying that the arm can't apply the correct tracking force without any sleeves on the counterweight?
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Old 20th October 2006, 11:06 AM   #3
fergs1 is offline fergs1  Australia
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greetings , actually the cartridge has its brass weight in place as although the ortofon literature says the weight can simply added or removed mine appears to be stuck in and i've never wanted to force it. Yes you are right regarding the tracking weight.I think the cartridge weight with insert is 5grams cheers fergs
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Old 20th October 2006, 11:19 AM   #4
EC8010 is offline EC8010  United Kingdom
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The weight is quite a tight fit, but there's a litle gap for inserting a small screwdriver as a lever. Perhaps if all else fails, removing the weight would bring it within range of the counterweight.
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Old 20th October 2006, 12:32 PM   #5
AMV8 is offline AMV8  United Kingdom
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Hi

I am not sure form the first post, but I think what you are saying is that the counterweight is too heavy with the rings attached and too light without any rings.

If that is the case try taping a small additional weight to the underside of the counterweight without any of the rings fitted. The hadcock arm counterweight is not rigidly connected to the main pillar/arm tube so the additional weight underneath does not need to be rigidly connected to the counterweight.

If you want the original rings I think I can find the phone number and address of Hadcock who has supplied me with spares in the past and is always very helpful.
Don
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Old 20th October 2006, 12:58 PM   #6
sreten is offline sreten  United Kingdom
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Hi,

In an ideal set up the OM30 is used without its weight in a low mass arm.

/sreten.
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Old 20th October 2006, 11:35 PM   #7
fergs1 is offline fergs1  Australia
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greeting thanks for all your replies, just wondering is the hadcock considered a low mass arm, isn't there a relationship between the mass and compliance of the cartridge and the effective mass of the arm? I'm afraid its all a bit over my head as far as understanding this but has anyone else had success mating the om30 with the hadcock. Prehaps AMV8 if you could provide me with George Hadcocks' details I could ask the man himself. Any other thoughts? Just wan't to add how grateful I am for this forum, and absolute wealth of knowledge and goodwill, thanks cheers fergs
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Old 21st October 2006, 01:21 AM   #8
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fergs1,yes there is a relationship between arm/cartridge mass and cartridge compliance,which ideally should give a resonance between 8-10 Hz.The OM30 weight is 5gr with a compliance of 25(dynamic).Hadcock recommend cartridge weights between 3.5-10gr so provided you have all necessary arm weights there shouldnt be any problem.Still,Hadcock manuals dont state clearly what the mass of the 228 is so I cannot say how the compination with the OM30 will be.However if the 228 has a mass around 10gr,resonance frequency will be around 8Hz with the brass plate fitted on the OM30 and around 9Hz without it.Best thing to do is to contact Hadcock especially for the counterweights.
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Old 21st October 2006, 09:29 AM   #9
EC8010 is offline EC8010  United Kingdom
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f = 1/2*pi*sqrt(m*C)

C = compliance of cartridge
m = total effective mass

From memory, I think the GH228 has an effective mass of about 6g, add 1.5g for screws, 2.5g for OM30 without brass weight, and you have a total of 10g. If OM30 compliance is 25 x 10-6cm/dyne, then that gives a resonant frequency of 10Hz, which is perhaps a little on the high side but perfectly useable.

There's really only one way to find out if it's alright - and that's to try it.
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Old 23rd October 2006, 08:03 AM   #10
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Default Hadcock counterweights

I understand that George Hadcock still has some spares for the early pick up arms. Or alternatively he could send you a modern weight and pick arm stub, his phone no is 01889 569166.
I have found, with over thirty years of using his arms, a very helpfull enthusiastic supplier in Gerorge Hadcok.
Hope this has been of help to you.
Stewart
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