Strictly Idler - drive that is!

Why do they sound so good?

Setting up the 78 auto stop ..........

Helpful instructions from Martin Kunz -

 

This is for all Lenco-users having trouble with the autostop feature in the Lenco L78. This instruction is for adjusting / repairing the autostop mechanism in the standard L78 with standard straight tonearm.

 

Please note that the 78’s autostop was basically intended to work on 33rpm and 45rpm records. As many of the older 78rpm records are cut off-center and may therefore wobble sideways, the L78’s autostop will only work on about 50% of 78s, no matter how good it is adjusted.

 

There are two different versions of autostop mechanisms found in the 78. Both work mechanically the same, yet a couple parts are different (the later version has been simplified for economic reasons).

 

Here’s the early version:

 

 

…and here’s the later version:

 

 

Please note:

All necessary works on the tonearm (like changing of V-blocks, works on the ball races, cleaning, wire-changing, etc) should already have been done before you start working on the autostop, to save time and work.

 

Okay,

 

1) Disconnect from mains and remove the platter

 

2) Tonearm: Remove the headshell and all detachable parts like weights, corkscrew, etc

 

3) Remove the deck out of the plinth. Place the deck on it’s corners, on woodblocks or similar

 

4) Check the tonearm for correct position(s):

The tonearm has correct height when the two pointed setscrews at the tonearm-base catch into a groove in the chromed pivot-housing (groove not visible from outside). To make sure they do, slightly loosen both setscrews (about 1/2 a turn). When you feel the arm comes loose, but still doesn’t move up/down – perfect.

 

5) Re-tighten the setscrews and check the tonearm for correct arm-rotation now. Counterclockwise movement of the tonearm MUST stop when the arm is located above the restpost. If it can be moved beyond that, fixate the tonearm at the restpost, loosen the setscrews again, then clockwise turn the arms’ pivot-housing (gently) until you feel a resistance. Make sure everything looks nice and parallel around the V-blocks area, then re-tighten the setscrews.

 

6) Make sure the “aut. / man.” -thumbwheel leftside the tonearm-base is on “aut”.

Now rotate the deck 90deg upright (tonearm fixated on the restpost, pointing upwards), and go underneath the deck. The tonearm has a metal lever with a slotted end attached to it, right where the arm-wires come out. With the tonearm on it’s restpost, the correct position of this lever looks like this:

 

 

Should the lever be far off that position, re-positioning is done by TWO 10mm hex-wrenches (A thin wrench just HOLDS the inner nut, a standard wrench TURNS the outer nut, while a third helping hand keeps the lever in correct position). PLEASE do not use any pliers for that job – a slipping pair of pliers easily damages / cuts the tonearm wires. If the levers’ position is just slightly off, I recommend to leave it as it is and make fine adjustments at the slotted end of the lever (it is slotted exactly for that purpose): Insert a matching screwdriver and widen or narrow the slot until the 2mm-gap (shown in the picture) is achieved. The smaller (=weaker) portion of the levers’ end will move. Finally, move the tonearm sideways and make sure the lever passes freely under the white plastic part of the lifter mechanism. If necessary, re-bend. The levers’ end is slightly bent down for that purpose.

 

NOTE: This lever does NOT activate autostop – it just brings Autostop into “stand-by-position”, so adjusting the position of the lever is not as critical as it may seem. What finally activates Autostop is a small metal thorn attached inside to the platters’ center bushing. Autostop is only activated in the outgroove of a record – that’s where the tonearm moves sideways faster than it does while playing a tune, and it is that faster sideways motion which shuts the machine off. Explanation follows later.

  

Fact is: When the tonearm is on it’s restpost and the slot-ended lever is mounted as described above, the mechanical autostop-parts are first involved in the game when the needle is 65mm away from the platters’ (center of the-) center spindle (see pic below). Or, 15mm away from an lp’s record label, if you wish. A 45’s record label is smaller, so again, parts are first involved when the needle is 65mm away from the center spindle, but distance to a 45’s label is about 22mm (part of which is the outgroove). This means that the tonearm may receive the sideways-“force” of certain autostop parts for a slightly longer period, when playing a 45.

 

 

7) Now place the deck back flat and let’s have a look in the snakepit on top J

Here we have the main troublemaker – a piece of a silicone tubing with OD = 8mm and ID = 5mm. Good ones have an almost “sticky” outer surface. Old, cracked and dried-out examples turn dark brown. When fresh it looks like this:

 

 

 

So first change this tubing to a fresh one if necessary (for 99% of L78s it is), then check for correct function (mains disconnected, tonearm on the restpost, yes?). The ON/OFF-knob brings parts “B” and “C” into position, as shown here:

 

 

 

8) The small “nose” marked in the circle must FULLY move from “OFF” to “ON”-position. When working correctly, part “C” already makes the full move while the mains-knob is moved halfway from OFF to ON. If it doesn’t, do the following:

 

Early version:

Remove the small copper blade-spring out and re-bend to make sure there’s enough pressure to move the silicone tubing. Re-mount the bladespring and check by flipping the ON/OFF knob a couple times. Important: In ON-position, the bladespring and tubing must NOT touch. In OFF-position, the white plastic cap at the end of part “B” must be furthest away from the platter spindle.

 

 

 

Later version:

Instead of the earlier blade-spring we have a tiny plastic lever (marked in green here) doing basically the same job. Often this lever goes out of shape and/or loses tension. It can be bent back under heat, for added pressure at the tubing. The heat of a small 15W soldering iron, positioned closely, yet carefully inside the “knee”, is enough. Be careful not to melt the plastic lever. Again, in ON-position, the lever and tubing must not touch.

 

 

Important for both early and later version:

Parts “B” and “C” MUST have a special start-position, when the turntable is switched ON. In ON-position - (and with the tonearm placed on the restpost) – the white plastic cap at the end of part “B” should be as far away from the platter spindle as possible. If this cannot be achieved for any reason, autostop will not work correctly or autostop may be activated shortly after the turntable is switched on.

 

9) L78 Autostop – mode of operation:

 

When switching the unit ON, the ON/OFF knob (and it’s linkage) brings parts “B” and “C” into position.

 

The L78’s tonearm moves free until the needle is 65mm away from the center of the platter’s center spindle.

 

The tonearm now begins to move both the parts “B” and “C”, which are slide-coupled.

 

Close to the end of the last track, a metal thorn attached inside to the platter bushing, begins to hit the sidewall of the white plastic cap at the end of part “B” and keeps it from moving on with every revolution. The thorn hits the cap where it is marked in green, which holds it back, while the tonearm keeps on moving part “C”. This goes on and on as long as there’s still music in the groove.

 

 

In the outgroove, the tonearm’s sideways motion speeds up and so does part “B”. This allows the platter’s thorn to hit the sidewall of the plastic cap where it is marked red, and this shuts the deck off, and lifts the tonearm as well.

 

10) Re-mount the deck into the plinth, re-assemble the tonearm with all it’s weights and headshell, etc.

 

Important: When putting the platter back on, make sure the thorn is located somewhere LEFT side the platter spindle! The thorn must not hit the plastic cap of Part “B” from the top.                                                                         

 

All the best,

Martin Kunz, July 2010

 

- 78 testbed

Sometimes ebay sales, with local pickup only, can get you a bargain. 

Trying some alternative arm wiring, a work in progress.

Latest experiment, arm supported vertically.

 

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