Recovery of an L78 SE

[Pockets]

Think there were  two different tonearms supplied originally with the 78 S , have  a look in the history section or someone  will answer if you put up a new thread in the tonearm section  . It may be  a Jelco tonearm .

[Pockets]

https://www.lencoheaven.net/forum/index.php?topic=28612.0   https://www.lencoheaven.net/forum/index.php?topic=41705.0   A couple of threads on the arm, think it was a jelco built arm for the lenco , not much info about it  ,meant to be based on the jelco 250 apparently.

[Kalimero]

Thank you for replying ...
Actually I am well aware that it is quite impossible to get spare parts of an arm  I jolly well have to look for other tonearms, but then it's quicker to replace it right away! 
Anyway, it's so incredible that there is almost no documentation about these arms even if they are not that old!! I mean they are out of the 70ties, it's only 50 years ago, did people threw away all documents, projects, drawings, publications, and so on? What is even worse that Lenco itself is not explaining in their manuals on how to adjust balance etc. Unbelievable!! In another thread about Lencos on a french forum someone wrote to Lenco and they were not able to tell anything about this tonearm 
I also found out (still on the french forum) that this arm is quite similar to a lot of others: Hitachi, Yamaha, Rega etc. I will have a look if spares on these are available, but I imagine they are not ... I like the "S" shape a lot so I am pretty curious on how this one will sound once I have finished. It will still take a while ...
Next steps will be the spindle and the idler wheel. I'll let you know.
Thank you so much again for your help.

[Pockets]

try soaking the arm in boiling water the rubber seat may rectify its position , maybe with some  judicial help with a suitable tool  that will not damage the bearing .  Try polishing the damaged cone bearing with some autosol or similar metal polish and then reassemble and adjust and see how the azimuth is .

[Pockets]

https://audiokarma.org/forums/index.php?threads/anyone-know-where-i-can-get-jelco-repair-parts.284483/ you may find that the bearings were used in other jelco  arms worth joining some other forums  and ask about spares

[Kalimero]

Ciao Mike (Pockets)! Could be an idea the one with boiling water. I think I first have to take out the wiring then ... I don't want to get it boiled too  So first I will try polishing the bearing cones, reassemble and then we'll see azimuth (just as advised).
Meanwhile I checked the spindle that was absolutely dry! Cleaned, oiled ... it should work fine again.
Some little troubles with the idler wheel. It was making a funny little noise. I oiled it first but nothing changed. I cleaned it again and this time I used vaseline as lubricant. Much better!! While looking for hints about the idler wheel I read macuser's thread about "Lenco idler wheel adjustment". Very interesting; so I checked the support of my idler wheel and the bias is really out of template. It's bent down a lot!

Some pics ...
Here you see the status of my idler wheel support:



It's absolutely not parallel to the chassis as Max (#macuser) is explaining in his guide ...

Pictures from other point of views:



As far as I can understand, this support can never be bent at the right level, as that "plastic arm" (beg your pardon about my English ... but let me know a correct word for it! ) is forcing the support itself down! We are now in "Off" position ...

In the next picture you can recognize it even better!:



What should I do?? I will ask Max in his guide, maybe he has the solution.

[Pockets]

That's normal, the arm should be checked for   level with the chassis with the spring removed and unplugged from power supply in the on position , search grommet twist for more info on correcting the sag, you need to twist the grommet within  the idler arm to correct ,  I  soak the grommet end of arm in boiling water and washing up liquid , makes it easier to twist with a dry cloth and rivitalizes the rubber somewhat .

[Kalimero]

Thank you Pockets. I'll do that right away. I misunderstood the "on/off" position ... 
I'll let you know ...

[Kalimero]

Back again ...
Bearing cones are fine! I polished them and realized that it was just dirt that was giving impression of being worn. It's just the one seat that doesn't look good. In a way or the other they pressed those seats inside, but I'm not going to try to press them out until I don't have a spare tone arm. Also the idler arm is fine now.
So this morning I wanted to make a sound test, I reassembled everything, put an old Audio Technica 110E in the shell and "off we go". I didn't have any alignment tool, so I just put the cartridge in the middle of the shell and tried: not bad for the first try  
Unfortunately I immediately noticed a strange hum once the needle is touching the vinyl   Until the arm is lifted, even with the motor running, I was able to raise volume up to three quarters without hearing anything (after the three quarters until full power a very little noise was audible) so I would say that there aren't any earthing or grounding problems. But once the needle touches the first groove then you can distinctively hear a sort of hum. It's a sort of ... It is like an extra vibration going into the needle ... of course you can listen to it until no music is played. Once music starts I cannot hear it any more.
I changed cartridge and put in a Denon DL160. Really nice sound, clear and very clean, even the lower frequencies were fully present. BUT that noise was still there. Here on LH I found the stylus gauge for my arm so I aligned it quite well. Sound was even better now, but that problem is not disappearing!
Conclusions:
- it's not the cartridge;
- I don't think it is the alignment;
- it's not earthing or grounding.
I would say that it's definitively not an electrical problem. The cause is not magnetic or electromagnetic. This is what I think so far.
Mechanical problems can be given by:
- the platter;
- the tonearm;
- the motor;
- the idler wheel or arm.
The platter: it is soooo heavy and I put the rubber mat;
The motor: quite noiseless;
The idler wheel/arm: some doubts ... the wheel is not that silent, but the noise you can listen to, once the motor runs, is not really constant. What I hear lowering the needle on the LP is a constant noise!
The tone arm: same doubts as above, even if I cannot believe that it can be those cone bearings ... .
Any suggestions? or what kind of tests should I do in order to find out what it is?
Thank you so much in advance for your help

[wenig watt]

If you can measure the frequency and come up with a multiple of the mains frequency, it is vibration from the motor. If there is a mechanical connection that is stiffer than it should be between the motor and the rest, you will get hum into the pickup via the vibration. Transport screws, stiff cables, incorrectly mounted decoupling...?

Best regards

Arndt

[Kalimero]

Hallo Arndt (wenig watt).
You're absolutely right! I couldn't go to sleep without solving this ... so, meanwhile, I went on thinking and while letting the motor run I accidentally touched the top plate. I could hear the echo of the touching through the boxes! So I made a test:
I blocked the idler arm, put the platter back in position and let the motor run. While letting the tonearm touch the mat (the platter was obviously still) I could hear that noise!! It is the motor! What surprise on one side and what delusion on the other.
Finally I know what it is. Doing then the same test on the L75 I also found out that, that noise was also audible here, but much less nearly nothing.
Regarding the motor now, I should find a way to insulate it better. Transport screws haven't been screwed in, so that's not. Tomorrow I will check everything in detail.
Thanks a lot Arndt.
Update will follow

[Kalimero]

Finally I solved the issue. Unfortunately I don't know exactly what it was. I worked on the motor, cleaned the bearings again, stretched the springs as they were not of the right length and finally I didn't tighten the nuts holding the springs to the very end. Result was, no vibrations any more. You can read what I did in this thread: https://www.lencoheaven.net/forum/index.php?topic=1609.30

Next step will be to dampen that echo that you can hear through the speakers every time you tap on your turntable ... Updates will follow

[Kalimero]

New updates:
If anybody read the thread about the hum ( https://www.lencoheaven.net/forum/index.php?topic=1609.30 ) you might remember that I didn't tighten the nuts holding the springs of the motor. I had to tighten them as motor was bouncing while switching it on ... I was lucky as vibrations didn't appear again.
I was thinking of damping motor and maybe also the top plate with some vibration damping material I bought really a long time ago for the car doors. I still had a bit left, but far enough for my needs. I began with the motor and then continued with some parts of the top plate.

This is the result:



I checked what I did and you cannot hear anything coming out of the loudspeakers while tapping on the top plate or the plinth. Really incredible! I would never have thought that it could work with just so little damping material ... Unfortunately I can hear that damned hum while lowering the needle on the LP again!!! 
It wasn't that bad as before, but it was distinctively audible when the cartridge and needle are reading empty grooves ... 
I tried to understand if the lower plastic base could have any influence as I just placed the plinth on the base without screwing them together. So I pressed the plinth down on the base and then, just by chance, I lifted it ... I couldn't believe it. Total silence!!
Next step was to try putting the plinth just on two pieces of wood with no absorbing feet. It worked! 
This is how it looks like now:



Of course I am confused now! How is it possible that you don't hear vibrations any more, just using two pieces of stiff wood??

[Kalimero]

I decided not to use the lower base any more. And so I am trying to build my own plinth. Very simple and quite similar to the original one, just a little bit higher.
Of course I found out that it is not that easy to build a plinth even if it is a simple one. Once it's done I will share pictures with you.

[Kalimero]

Some pictures showing the work in progress: