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Lenco L65 hums, only when playing

Nope

Unfortunately, that doesn't seem to be the solution to my problem, Fernando. I removed the screws (the same two red screws under the platter of my L65, indeed), and I still hear the same hum.

And for those who want to hear the hum we're talking about, I added it in a ZIP-file. Best heard with headphones.
 

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RudyVerkorst said:
Unfortunately, that doesn't seem to be the solution to my problem, Fernando. I removed the screws (the same two red screws under the platter of my L65, indeed), and I still hear the same hum.

And for those who want to hear the hum we're talking about, I added it in a ZIP-file. Best heard with headphones.
Click to expand...

Perhaps it is a problem with the power supply within the table? I'd look closely at the electrical components, just in case a capacitor or circuit break is allowing AC through to somewhere it doesn't belong.

A total shot in the dark, but worth a try even just to have a good look inside the unit. Did it always do this?
 
Everything looks fine one the power supply, and I don't see any motor suspension, the only suspension I see is that the whole chassis plus platter is suspended to neutralize footsteps and so.

I removed the DIN cable and soldered a brand new cinch cable to the wiring strip. Result: the same hum.

Then I removed the connection between the left ground wire and the chassis on the wiring strip (why is it there?), and soldered a cable from the chassis (in the middle on the wiring strip, isn't it?) to the chassis of my amp. The same hum stays.

And why is there a metal tag on my cartridge that connects the left ground channel to the shield of the cartridge?

Strange thing is that my left and right ground cable in the arm seem to be connected somehow, according to my ohmmeter. Is this okay?
 
The Vinyl Engine has the manuals for the L75 and others but not the L65. In the L75 manual there is an underside picture. (page 8) It shows the motor assembly with the tapered horizontal shaft and 3 springs at the corners. When the transit screws are removed, the entire motor assembly separates from the chassis and remains suspended by these springs. If there is anything binding on the motor assembly, vibrations could be transmitted. I do not know if the L65 uses a similar mechanism.

Fernando
 
Unfortunately, the L65 is totally different, Fernando. See a pic of my motor in an earlier post of this thread.

Where could Fred, John and Mopic be with their good advice? Should I try a new cartridge? Shure, Audio Technica and Stanton are the ones my vendor has.
 
Hi Rudy,

Sorry for the “hiatus awayness”, but I haven’t forgotten about you and your humming L-65. I e-mailed a couple of the guys over at LL after entering pics of your turntable in a “Name that Lenco Contest”. There’s a bit of head scratching over this one – but only on cause - not on the troubleshoot process.

I think getting another cart – or borrowing a run-of-the-mill used one - just to get this unseeable possible problem area into/out of the equation is a good start. If the replacement cart still produces the hum then I’d unsolder all arm wiring from that terminal strip.

Even though your symptoms don’t point to it, I’d check all the tonearm wiring for continuity – just for good measure.

If the tonearm wiring checks out, cut up some phono patch cord and solder connections (4) for the 2 channels. Solder two ground wires to the tonearm groundwire – make ‘em long enough or the following:
1- Attach one directly to the negative post for one of the speaker outputs on the back of your amp (commingled with the speaker wire).
Test the system. If you still have hum …
2- Use the second test ground wire to make contact to various chassis points or “equipment grounds” on your Lenco ie. motor mount screw - main bearing sump mount screw (I have an L-61 that strings grounds between both because of grease isolation on the motor mount springs – but not your problem).

If after checking various chassis grounds combination and you are still left with a hum.
Abandon this 2nd commingled test ground and make a third ground test wire. Hook up one end to any place that you can make contact with the arm stub and the second end …
First, to the negative speaker post;
Hum still present? Then..
2nd to the ground post on the back of your amp/preamp
Hum still present? Then..
3rd to an equipment ground of the Lenco chassis
Hum still present? Then..
Use another ground test wire to hook this 3rd setup to the Neg speaker post.

Ground Gremlins bedevil almost all of us at some time in the vinyl game – and they can be tough to pin down. Using an organized troubleshoot can help, even if it seems like going back to square one. And we haven’t even touched on proximity issues…

“After one eliminates all the probable causes, whatever is left, no matter how improbable, is the real cause.” – Sherlock Holmes

- Mario
 
I've been gone for a long time, I'm almost back. I just msg to say that I bought a brand new Audio Technica cartridge, connected it to the headshell, but the hum stays. I don't really get what all this wiring tests are about, Mario, but I think I'll try them when I have more time for it. If anyone else has other advice, don't hesitate...
 
Rudy,

Once you get the ohmmeter check from where the audio cable is soldered on to the table to the four pins inside the arm (with the cartridge shell off). You should find continuity from each of the four pins to each of the solder points. If not, you have an opened wire and that is "lifting" ground.
 
Hi Rudy,

Does your amp have regular phono inputs as well as the 5-pin DIN? If so, I'd abandon the DIN, at least, for the sake of troubleshooting. If it doesn't, make sure you don't hook up any ground to it for any of the ground tests that I mentioned above. (This dedicated ground on the DIN could create looping (more hum!) on the tests.)

While the above troubleshoot may seem squirrelly and complicated, it shouldn't take more than 20-30 minutes. With it, you're basically severing all ground and signal relationships at that terminal block (do take notes on how to restore it). Then you begin to reconstruct ground relationships with free wire (basically a floating terminal block). What you're testing for is to find the proper relationship between a) the motor/chassis grounds and b) tonearm ground - and to what degree they need to be commingled or divorced.

After re-reading this thread, there's and additional area to check on the tonearm ground wire. Is there continuity from its attachement end (when unsoldered) to the threaded stub of the tonearm?

- Mario
 
The connection inside the tonearm seems okay.
Then I tried all the wire tests, but nothing worked...

I'm close to throwing him out of the window... No, I'm joking. But still...
 
Hey Rudy,

Can't believe you're still saddled with this!
I've gone back and re-read this thread twice and it seems that we should have throttled it by now. But if you're up to it, let's wipe the board and start from the top and maybe somebody will weigh in on something missed.

First, is this hum ever-present when the turntable is switched on - or only when the stylus is applied to a record or finger?


Do you have a hum when the headshell is removed from the arm?

Have you bypassed your DIN connector or is this not possible?
 
Thanks a lot for you answer again, Mario. I did all the tests you mentioned, except the last step ('use another ground test wire to hook this 3rd setup to the neg speaker post') because I didn't understand how much wires had to be connected to what. I really hope I did the tests correctly.

The DIN-connector is gone now, I soldered a brand new cinch-connector.

The hum is only present when the motor is turning and the needle is touching the record or a finger.

When I remove the headshell, I hear a lower, louder hum.

Another strange thing is that when I want to put a record on the platter, I can hear a sound like 'chick' when I'm nearing the platter. When I move away the record, I hear the same sound. It reminds me of some kind of static electricity....

When I touched the motor screws or the chassis in the above mentioned tests, I could also hear some 'chicky' sounds (more like scraping), but the hum stayed.
 
Is it possible that an old med school question may have bearing on this?
"What fracture is the most overlooked in medical care?"
The answer - "The second one." (Referring to the human tendency for docs to stop looking further after a first break has been diagnosed.)
Could it be that trying to solve Rudy's hum issue with a "one correction fixes all" solution - might be a stumper because there is more than one fracture of the ground?
Just stirring the pot on this...
 
Hi Rudy,

Sorry I'm late to this party, and excuse me if I ask questions already answered.

Did this table spend a long while in storage? Has the recent use ever been hum free? In other words was it put away faulty? Has anything you know of changed since it was working ok, to now?

Does this model have the signal interrupt switch linked to the arm, so it's not connected till the stylus touches vinyl? If so then it's probably in fault all the time, you just don't hear it till the needle drops.

If you've ditched the din (hooray!) and fitted phono plugs for the amp, it's a good idea to snip the link from the channel -ve and gnd, and add a new separate gnd wire from the deck to the amp.

The noise you are hearing when touching the deck screws indicate the deck metalwork is not grounded.

I'm just catching up.

Regards
 
I don't know if it is normal, but it seems that there is a connection between the chassis of my amp, and the grounding channels of all connectors. Maybe the problem is not the tt, but the amp... Unfortunately, I don't have another amp (with phono input) to test it.

This tt was possibly a long time nog used because I herited it of my grandparents. The hum probably was there since I got the tt, but it didn't bother me till now that I want to digitalize my records.
 
Fernando said:
I do not know about yours but I am very familiar with the Lenco L75. These used to have 2 transport screws under the platter to secure the motor. If these were not removed, the motor suspension was bypassed and vibration went straight to the chassis. It was a mechanical hum only heard when the stylus was on the record. Many dealers did not know this and delivered the units with the motor transit screws in place. The difference once removed was astounding. Check your manual. Atlernately remove the platter and look for 2 screws with red marks.

Fernando
Click to expand...

Fernando,

This solved my 60Hz hum 14 years after you posted this. Removed the transport screws and L78 sounds like magic! Thanks so much.

Wei
 
RudyVerkorst said:
I have a Lenco L65 with Stanton 500 cartridge of the old days, and whilst playing, it produces a significant hum. This means it hums while the needle is on the record (or on my finger) AND the motor is switched on.

I've opened it, and everything seemed normal (as far as I could see - the connections inside the arm bearing are impossible to see). When I try to wire the arm with the chassis, nothing changes.

As I could read on Graham Slee's site, there is a metal tag that connects the left channel ground to the chassis of the cartridge. According to Slee, it could give a hum loop when the arm is properly earthed. I didn't remove the tag as it has always been there, probably since my grandpa bought it back in the seventies or sixties.

Please, help!

Thanks
Click to expand...
Your problem is the Stanton needs to be isolated. They come with plastic isolation blocks ie they cant touch the headshell or you get big hum. The bolts and headshell must not conduct to the headshell. Then no hum.
Chris
 
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