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Lenco L70 project

Seems everyone and their uncle are turning out J-shaped, and especially S-shaped, tonearms without bothering to include lateral counterweights these days.

Have these been deemed as un-necessary in the new millenium for some reason?
 
I don't see any good reason for a lateral counterweight unless you're using a unipivot or a knife edge vertical bearing.

Paul
 
I thought it was a knife edge bearing thing - I've never seen a j or s shape uni, and would imagine it would be a total nightmare if someone were to try.
 
Well, a good many S-shaped gimbal bearing tonearms included lateral weights at one time.

These being provided as a means of overriding the natural tendency of these lopsided contraptions to drift one way or the other should the playing field not be absolutely perfectly level (which, in practice, it rarely ever is).

The usual technique for adjusting these was to zero the anti-skating mechanism, balance the arm such that it floated level, and then raise the back of the deck by ~15 degrees such that the position of the lateral counterweight could be adjusted until the arm lost its tendency to sway one way or the other of its own accord.
 
Then what happens if you raise the side of the deck by 15 degrees? I think there's no significant point unless you need to balance out the masses to make the bearing work. And I assume none of these arms used the counterweight to apply tracking force?

Paul
 
Paul Ranson said:
Then what happens if you raise the side of the deck by 15 degrees?
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Why would you?

The adjustment is presumed to be carried out with the deck in situ upon its playing support.

For convenience, it can also be performed by raising the front of the turntable.

I think there's no significant point unless you need to balance out the masses to make the bearing work.
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I would speculate that LR pairs of bearing races might offer a more similar minimum resistance to movement when the supported mass is evenly distributed between them.

With the cartridge and mounting hardware combined mass being an unknown, on S-shaped (and especially so on J-shaped) tonearms this even distribution of load cannot be the case unless some form of lateral balance adjustment is provided.

However, having speculated that, from what I've managed to gather from the various manufacturers' user documentation, the reason for the inclusion of these on gimbaled bearing S or J-shaped tonearms appears to have more to do with anti-skating being set to 0 as actually being equal to 0 - that is, somewhat independent of the turntable WRT it being perfectly level.

And I assume none of these arms used the counterweight to apply tracking force?
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Most all of the lateral weights I've seen and/or used are positioned aft of the bearings (LH side on S-shaped and RH side on J-shaped) so, yes, in most cases their position must be taken into consideration WRT balancing the tonearm fore/aft as well.

Craig
 
gortnipper said:
Hey Tony - there is a Hadcock 242 Super Silver for $900 US on A'gon.
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Thanks, but I've already got one - it's the arm I use on my Spacedeck:

spacedeck2.jpg


The decision with the Lenco is whether to go for a 2 armed deck with the Hadcock on the back and L70 arm in it's standard position, or to go for a single 12" arm such as a Shick mounted at the side.

Tony.
 
I think Tony needs two arms on his Spacedeck + the two Lencos.
The Hadcock looks awfully lonely in that picture.
 
Blimey, I paid over 100 each for mine and still felt like I got good value! Is your a nice one?

Tony.
 
Photo looks pretty grotty but it's difficult to see the real condition under the green tinge! I guess I will find out when I collect it. There's no plinth, so it's not as original as your number 1 Lenco. It looks about the same style as the one you re-sprayed, but the arm looks like the GL75 one I have. I don't really know my Lencos, but I thought the arms on these were somewhat different?

http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&rd=1&item=150226426480
 
This site contains affiliate links for which pink fish media may be compensated.
It's a nice early light grey one with the small name plate so same period as mine, i.e. it will date from around 1960 to 1964. The arm has indeed been replaced with an L75 arm, which is a shame as a) it doesn't fit (wrong length) and b) it's far worse. The original L70 cueing device is still there. What do you intend to do with it? The arm hole is IIRC about 225mm away from the centre spindle so Regas and the Hadcock 242 etc fit in a geometry sense but you can't get VTA in without a thickish platter extension.

Tony.
 
It's actually for a friend, but an RB250 or Terminator // arm and a slate plinth might be on the cards.

I will have it and a GL75 shortly, so I will measure the arm mounting distance as accurately as possible and post the results. You can put them on the Lenco Lovers forum as there seems to be a good deal of vagueness about what they actually are and what arms will fit!

I don't think VTA is a real problem - the Cartridgeman makes an isolator http://www.thecartridgeman.com/isolator.htm that would probably do the job. A DIY version is also an option.

The Terminator arm will go plenty low enough.
 
I've just measured mine as best I can with the arm in place and get about 228mm, i.e. the L70 arm is a long one! A Hadcock 242 would certainly fit perfectly (bar being about 1cm too high), the Rega would need the hole drilling out a bit as the L70 arm has quite a small diameter base (though this will no doubt have been done to an extent to fit the L75 arm). Does the Terminator mount on the deck or plinth?

Someone over on LL has just tried a Slatedeck plinth and really liked it which has surprised many of us as it doesn't support the underside of the 'pan' in any way and this was considered to be the deck's key weakness, i.e. it is a comparatively flimsy and resonant pressed steel structure. Conventional thinking was that it needed to be coupled to a non-resonant CLD structure as close to the main bearing as possible. Just goes to show there is no 'right' approach.

Tony.
 
Hmm... 1cm too high is quite a lot! The LL forum is very vague on thing like this! The Terminator arm will mount off the hole in the deck - the mount is cantilevered, and will basically fit anything. It may be Vic (maker of the Terminator arm) who has posted about the slate plinth on the LL forum, I'll take a look.
 
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