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Beogram 5500 Tonearm/MMC4 problem

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kightley
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kightley posted on Fri, Mar 10 2017 7:42 PM

I'm a newbie to the forum, so forgive me if I seem a little slow!

I have a Beogram 5500 fitted with an MMC4. All in working order, except that when the tonearm lowers onto a record, the sound is very distorted - until I gently tap the end of the tonearm down. Then the MMC4 "settles" about 1mm lower, and the sound becomes perfect. It's as if there is not enough tracking force, but I've checked it at 1.4 grams, which is actually a little high. Everything else looks ok, and there doesn't seem to be anything else preventing the arm from dropping the last little bit. I've taken the cover off, and checked all internal workings - all seem ok. With no platter in place, the tonearm lowers perfectly to the bottom of its travel.

I wonder if the MMC4 may have a problem with its suspension? The needle, cantilever etc all look fine under a microscope.

Any suggestions most welcome, and thanks in advance.

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Needs a Nickname
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Saint Paul, Minnesota
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Yes, that sounds like cartridge suspension to me too. Check this nice write up

http://www.sound-smith.com/how-know-when-your-bo-cartridge-may-have-failed

Peter-

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Needs a Nickname
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Saint Paul, Minnesota
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Yes, that sounds like cartridge suspension to me too. Check this nice write up

http://www.sound-smith.com/how-know-when-your-bo-cartridge-may-have-failed

Peter-

kightley
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Thanks Peter, I think you're right.

I had a good look at the cartridge under the microscope, and to my mind the cantilever arm seemed to be a little low. It took a slight amount of force to lift it to the neutral position, which suggests that it may be getting magnetically stuck to the upper pole of the "horseshoe".

As an experiment, I wound a length of very fine wire around the nose of the cartridge, under the cantilever, to lift it slightly into position. This worked - when the tonearm dropped, it played the track without distortion. Bit of a bodge, but seems to prove the point.

So now, I may have to get a replacement cartridge - but they do seem to be extortionately expensive on ebay, so may have to wait a while. The whole Beogram only cost £36 when I got it on ebay a few years ago! MMC4s are going for £300 now... 

Thanks for your help :)

Needs a Nickname
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I've had carts rebuilt from Hans-Henrik aka 'pickupserivedk' from eBay and been very happy. I prefer rebuilt over used or NOS any day. The soundsmith carts are fantastic as well and I've had hundreds of happy hours from them.

Beoworld'ers speak highly of

https://www.tonabnehmerservice.de/en/B-O-Restoration/Recovery-MMC-1-5-All-images-used-sample-images/

These tables are all about the cartridge IMHO, very much worth it.

Peter-

kightley
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Thanks again Peter. Advice much appreciated.

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