foxwelljsly
Me too, I ate one sour too.
That is exactly where I'm at. Unfortunately, the armlift for the Revolver badged Jelco arm protrudes far lower than the armlift mechanism on the Jelco Badged ST250, which limits how far it can be dropped.
Lenco GL75 recommissioning
- Thread starter foxwelljsly
- Start date
foxwelljsly
Me too, I ate one sour too.
Just done something similar and stuck a 3mm felt mat over the rubber mat.
2-4 mm of headshell shims should now get me perfect.
foxwelljsly
Me too, I ate one sour too.
In the unusual event that anyone wants an unusually well preserved and complete L75 tonearm, give me a shout.
foxwelljsly
Me too, I ate one sour too.
I can definitely hear some kind of vibration noise coming through. I guess those rubber v blocks were designed to provide some kind of isolation.
Once I have this one working nicely with a Jico SAS stylus, the next stage may be a custom plinth which could accommodate both Rega and 12" arms.
Helen Bach
if it ain't Baroque ...
Make sure the (usually) red transportation screws are NOT tight. The rubber v-blocks would have offered some isolation (due to mechanical impedance mismatch) but very poor at containing the arm. Also, I advise NOT building a massive plinth, again mechanical impedance mismatch will reduce the vibrations in the top plate from reaching the plinth (they will be reflected) so then you have to take remedial action in damping the top plate. Also note, mass doesn't damp. HTH
foxwelljsly
Me too, I ate one sour too.
I am tempted to try:
-decoupling the collar from the top plate using rubber washers
- replace the the hardened rubber grommets that decouple the top plate from the plinth with something sorbothane
- do the same with the hardened rubber feet on the bottom of the plinth
- stick the whole thing on a slate plinth with sorbothane feet.
Dowser
Learning to bodge again..
It shouldn’t be like this, I’ve bought/serviced/resold many (always with a different arm mounted to stock top plate) with no such issues. Have you stripped/cleaned/re-lubricated every moving interface? Kind of essential. Pay special attention to how the idler wheel is attached to the idler arm, this can cause definitely vibration - I’ve had 2nd hand worked on before players missing essential washers, and you really need to clean/re-lube the brass bearing it sits on. Wrapping the idler arm in plumbers tape can also help, as well as making sure the guide for the arm is re-lubed. Good luck!
narabdela
who?
Helen Bach
if it ain't Baroque ...
De-coupling willy-nilly (techno-term!) is not going to improve anything. Certainly not the arm support. NEVER add decoupling between arm and turntable. The best advice is to mount the tone arm off the top plate, and use a better arm than stock. The original top plate resting on the original chipboard plinth is preferred to any mdf/ply/slate monsters. De-coupling the above with springs brings much better isolation, as does a support made of something which actually damps. Ply/mdf/slate don't (much at all!)
Tony L
Administrator
Not sure I agree with that, I suspect it is a little more variable depending on context. After playing about I certainly prefer vintage SME arms installed following SME’s instructions to the letter with their rubber baseplate grommets to just bolting the baseplate to the armboard. Exactly as in the manual, i.e. grommets not mashed-down at all. That’s obviously just one type of arm and one armboard, I’d not make the same argument for say a Rega or Ittok, though I certainly find the RB300 sounds a lot better with its mounting nut as loose as you can get it without the arm moving when using the cueing arm.
With the Lenco arm (assuming I wanted to use one at all given it is such an extreme case mass wise) I’d want to at least start from the original design, i.e. find ‘V’ blocks of a very similar damping properties to the originals as I’d expect they were made that way for a reason. FWIW I don’t recall much rumble at all from my original Lenco back in the late-70s. That was with the original v-blocks.
Helen Bach
if it ain't Baroque ...
Interesting, Tony. I believe the little rubber SME grommets were to 'isolate' the arm base from its support (arm board, etc.) Unfortunately, this could lead to 'wobble' at the microscopic (cf groove dimensions) level. Obviously, SME thought vibrations were getting to their arm from the arm board. But 'isolation' also means the structure which is isolated has to deal with vibrations all on its own. Very few may. As regards the Rega, it is well known that 'nut and bolt' connections have a certain degree of damping, compared with a welded structure (with buildings, not hifi!).
With the Lenco arm, it's a bit of a 'Curate's egg' (good in parts). The rubber v-blocks are a nightmare, not allowing the support and rigidity needed for a decent arm. However, I do like the horizontal bearing. Doing the 'Linn swing' thing, the Lenco arm swung 235 times!! and because of that I am building an arm with the Lenco horizontal bearings, the v blocks have been binned.
With the Lenco arm, it's a bit of a 'Curate's egg' (good in parts). The rubber v-blocks are a nightmare, not allowing the support and rigidity needed for a decent arm. However, I do like the horizontal bearing. Doing the 'Linn swing' thing, the Lenco arm swung 235 times!! and because of that I am building an arm with the Lenco horizontal bearings, the v blocks have been binned.
ff1d1l
pfm Member
Some years ago I built a Lenco into a slate plinth - I filled and reinforced the Lenco top plate with marine epoxy too, and used a leather gasket interface between the slate plinth and the lenco top plate. 12" Sme, I don't think I used rubber grommets.
Sounded very good, noticably better than the Linn it replaced (No doubt a whisky cask Linn plinth would have changed this result though.)
Sounded very good, noticably better than the Linn it replaced (No doubt a whisky cask Linn plinth would have changed this result though.)
Tony L
Administrator
I’m neither a physicist nor an engineer, but the way I visualise it is a design compromise between resonance, damping and stability. No simple answer here, only compromise. I don’t buy in at all to the “rigid” argument in hi-fi as everything resonates, and often the more rigid it is the more it resonates (tubular bells anyone?). Dealing with resonance is the key, and there are a whole range of valid approaches here from a golf-ball in gloop onwards. I certainly don’t buy into the “feels rigid in my hand/looks rigid, therefore it is rigid” argument, in fact I think that this simplistic thinking is a factor why so much audio kit made since the ‘80s sounds so bad (I’ve regularly used a ‘tuning fork’ argument as exactly what one doesn’t want!). What is important is resonant behaviour and damping at audio frequencies and very few turntable, tonearm, speaker or stand manufacturers have the ability to accurately assess that so really we are just bludgeoned to death with barely literate marketing guff.
I’m surprised by that as last time I looked at a L75 arm (about 15 years ago) lateral bearing I actually ended up parting the deck out as the lateral stiction was so great it couldn’t even get an AT95E across a record without sticking. The lateral bearing reminded my more of a bicycle wheel than a turntable, but maybe I had a particularly bad example. My original one back in the late-70s-early-80s worked ok with an M75EJ.
Did you strip the bearing right down to clean it? I didn’t, couldn’t be bothered time-wise for a deck which wasn’t worth anything more complete than in parts.
PS FWIW I think the Linn ‘swing test’ is only of use to establish if some idiot has cranked the VTA bolt on an Ittok or Ekos so hard as to bend the bearing housing and distort the ball-races. It tells very little about the arm works with the bearings loaded as they are in use. I’d not extrapolate it to other arms. It is really just a tool to indicate dealer/user damage to a Linn arm that regularly occurred due to the marketing culture.
Helen Bach
if it ain't Baroque ...
I'm not a physicist nor an engineer either, although I have three science degrees and I have been investigating 'damping' for the last 15 years. I realize that the damping phenomenon is not well understood, especially by audiophiles. I wouldn't agree that design is a compromise between resonance, damping and stability (not all vibrations are resonances, but resonances are the most important to ameliorate against). For example, a Rega arm can be damped (internally) and mounted on a damping arm board with the same mechanical impedance (MI) as the base of the arm, although I am not aware of any manufacturers mentioning this. If the MIs are the same, or very near, the vibrations from the arm will transfer to the arm board, which, if made of a damping material (most aren't) the vibrations will be damped (out of existence!).
I didn't do anything to the L75 arm (I have several!) so I guess I was lucky and you weren't. Depends on how they were stored, I guess.
My daily driver is a Lenco 75 rigidly mounted in an original chipboard plinth, and isolated by non-Lenco springs on a bamboo and oak support. The Rega arm is mounted to one side of the plinth on its own arm board/pod. With a Linn K18 body and Black Diamond nude stylus, it gives me great pleasure. [I am a music lover, not an audiophile!
]
When I bought the Lenco, it had every 'damping' method applied known to man. The Lenco had rumble 'in spades'. I removed ALL the damping and rubber grommets, and mounted it as mentioned above. Although I can still hear a very small amount of rumble if I place my ear to the speaker/s, I put this down to an un-lubed motor. Next job! Moral: understand what you are doing, or you could make matters worst!
I didn't do anything to the L75 arm (I have several!) so I guess I was lucky and you weren't. Depends on how they were stored, I guess.
My daily driver is a Lenco 75 rigidly mounted in an original chipboard plinth, and isolated by non-Lenco springs on a bamboo and oak support. The Rega arm is mounted to one side of the plinth on its own arm board/pod. With a Linn K18 body and Black Diamond nude stylus, it gives me great pleasure. [I am a music lover, not an audiophile!
]When I bought the Lenco, it had every 'damping' method applied known to man. The Lenco had rumble 'in spades'. I removed ALL the damping and rubber grommets, and mounted it as mentioned above. Although I can still hear a very small amount of rumble if I place my ear to the speaker/s, I put this down to an un-lubed motor. Next job! Moral: understand what you are doing, or you could make matters worst!