Could use some help with a DIY turntable mishap (Lenco L60)

[JaccoW]

So I have been enthusiastically modding the old Lenco L60 turntable my parents gave me and have been overhauling and rewiring it... and breaking and repairing some other parts.

Some of you might be glad I listened and redid the power wiring inside to standard colours (most notably @sergeauckland and @Suffolkhifinut ) but now that everything is back together I have a distinct lack of high-frequency sound and no idea where to go to next...

Original wiring:
The original wiring used a fixed cable for both power and the RCA connector and they were old and falling apart. I also wanted the ease of use of removable RCA cables so I added sockets. The original wiring has a connector grounding the tonearm to the left signal which causes a hum sometimes.




First modification:
Using the schematics below I grounded the tonearm and power cable and added a pair of RCA sockets.

Understandably, I got some comments on here about the wiring and if it was all safe. It sounded pretty good however.









Second modification:
This is where things started to go wrong.

The simple RCA sockets cracked and twisted so I decided to replace them with some sturdier Neutrik phono RCA chassis connectors. While doing so I snapped one of the tonearm wires, so I ended up replacing those with Cardas 33awg shielded tonearm wires, directly soldering them to the cartridge to headshell leadwires and the neutrik connector without the little brown connector plate inbetween.

Cartridge > Leadwires = tonearm wires > RCA socket

I also tidied up the motor and grounds wiring but when I plugged the mains cable in, the entire house went out... Eventually I managed to track it down to the C14 connector itself. I could see nothing wrong with it but it even shorted the house when I would remove all wires and took it out of the chassis with only a short bit of the live wire attached (but that one connected to nothing else, just the bare connector). Even that was enough to take down the house. The fuse in the connector came through unscathed so it was probably something even before the power entered the turntable? Anyway, desoldered, cleaned and redid everything and now it works perfectly fine.

So, sockets + connector done up, time for some playback.
Sounds horrible, like all the high-frequencies were being filtered out. Not necessarily a rumble but just a lack of high-frequency sounds like cymbals.



What now?:
So what can I do now? I checked the classic culprits.

1. Azimuth
2. Tonearm balance + needle pressure
3. Cartridge alignment
4. Phono preamp? Checked with a different preamp and not much difference.

I'm a bit at a loss right now what could be the issue, perhaps someone has an idea? I can think of a couple of issues but most are fairly time-consuming to troubleshoot.

• The shielded cable is too thick and dampens the tonearm somehow?
• Damaged the tonearm bearings?
• Soldering the tonearm wires into the headshell leadwire terminals uses way too much solder and should be done directly?
• RCA sockets are way too heavy duty and filter some of the sound?
• Bad soldering connection of tonearm wires to RCA sockets?
• Damaged the cartridge itself when the fuse blew?
• Something else?

Like I said, not sure where to go to next. If anybody has an idea that I have overlooked or a suggestion what to check first I'm all ears.

And yes, I know I'm dangerous with a soldering iron. It's a learning experience alright.

 

[JaccoW]

Now that I look back at those earlier pictures, I can at least try to check for potential issue #1. Originally the tonearm wire came out from the back of the hole in the chassis instead of the side like it does now. As it is now it pushes inside of the hinge and probably explains the slight anti-skating issues I'm having.

Something to check tomorrow I guess.

Bonus picture of the new RCA sockets:

 

[Chazz6]

I know nothing of all this, but I wonder about one thing. Probably nothing, but does the blue wire have a good connection around the screw?

 

[paddycrow]

I would try to get more wrap around the screw with the blue wire. It may need a washer.

 

[JaccoW]

I know nothing of all this, but I wonder about one thing. Probably nothing, but does the blue wire have a good connection around the screw?

I knew I should have added a clearer picture of the new situation.

Here is what it looks like now:


I drilled a hole through a washer and soldered it on.

 

[JSmith]

@restorer-john ... is this your cup of tea?


JSmith

 

[sergeauckland]

If there's a lack of high frequencies, that has nothing to do with the turntable electrical wiring, it has to be on the audio side somewhere. Firstly, what is the cartridge, and are you sure you've connected the four cartridge pins correctly to the arm wires? Secondly, do you have a specification for the capacitance of the arm cabling, and what cabling goes from the Neutrik sockets to the phono stage? Thirdly, what's the phono stage and the load it presents to the cartridge?

My Lenco L75 is fine for frequency response on both MM and MC cartridges, and I expect yours should be much the same even if the two turntables are quite different in construction.
S

 

[tonycollinet]

I would also be worrying about the thickness of the tone arm wires. they don't look very fine to me. How are they compared to the ones you replaced? Tonearm wires need to be ridiculously thin so they don't create any mechanical resistance to the tone arm rotating about it's pivot, due to their stiffness, or mechanical friction if they rub *at all* in the pivot of the tonearm. If they do, then the stylus is forced to the outside of the groove as the wire stiffness/friction is overcome. I'm guessing the ones you replaced were not shielded, and the shielding will add a lot of mechanical stiffness.

This would include the earth wire you've run up the underside of the tone arm - how thick is this - how much resistance is it creating to the tracking of the tone arm?

 

[JaccoW]

If there's a lack of high frequencies, that has nothing to do with the turntable electrical wiring, it has to be on the audio side somewhere. Firstly, what is the cartridge, and are you sure you've connected the four cartridge pins correctly to the arm wires? Secondly, do you have a specification for the capacitance of the arm cabling, and what cabling goes from the Neutrik sockets to the phono stage? Thirdly, what's the phono stage and the load it presents to the cartridge?

My Lenco L75 is fine for frequency response on both MM and MC cartridges, and I expect yours should be much the same even if the two turntables are quite different in construction.
S

Yeah I figured it was on the audio side of things.

The phono stage is the built-in (MM) phono stage of the Argon Audio Forte A5 and it sounded fine before replacing the Neutrik connector and the tonearm wire but I had to change too many things at once to rule out one of them right now.

I'll check the connectors on the cartridge.

Cartridge:
Audio-Technica AT-VM95E. I did damage the needle in the past and had to replace it. (It sounded like it caused a lot of rumble)

Wire:
Cardas 33 AWG wire

Measured at (Audioasylum)

Capacitance	.019 nf / 19 pf. 3.8 pf per ft.
Contact resistance	1.5 ohms or 0.3 ohms per ft.

Connector:

Capacitance between contacts	≤ 9 pF
Contact resistance	<5G mΩ
Dielectric strength	0,5 kVdc
Insulation resistance	< 5 GΩ
Rated current per contact	16 A
Rated voltage	< 50 V

 

[JaccoW]

I would also be worrying about the thickness of the tone arm wires. they don't look very fine to me. How are they compared to the ones you replaced? Tonearm wires need to be ridiculously thin so they don't create any mechanical resistance to the tone arm rotating about it's pivot, due to their stiffness, or mechanical friction if they rub *at all* in the pivot of the tonearm. If they do, then the stylus is forced to the outside of the groove as the wire stiffness/friction is overcome. I'm guessing the ones you replaced were not shielded, and the shielding will add a lot of mechanical stiffness.

This would include the earth wire you've run up the underside of the tone arm - how thick is this - how much resistance is it creating to the tracking of the tone arm?

Sounds like the way I setup the way I set up the tonearm wire might be suspect. Would it help to strip back the wire to the tonearm itself and just have the thin wires running through the arm pivot to the RCA connectors?

The ones I replaced were unshielded. Would it be possible to ground the tonearm through the shielding by running a very thin wire from it?

Right now the shielding goes all the way until shortly before the RCA connectors but I did realize I ran it throught the wrong hole so it turns with the pivot itself.

EDIT: Like this:

 

[tonycollinet]

Once the wires have exited the tone arm, it doesn't much matter. But if you have the thickness shown in that picture running through the tonearm, and especially the pivot, then that is probably quite bad. Even in the arm it will be influencing the mass and resonances.

 

[sergeauckland]

Sounds like the way I setup the way I set up the tonearm wire might be suspect. Would it help to strip back the wire to the tonearm itself and just have the thin wires running through the arm pivot to the RCA connectors?

The ones I replaced were unshielded. Would it be possible to ground the tonearm through the shielding by running a very thin wire from it?

Right now the shielding goes all the way until shortly before the RCA connectors but I did realize I ran it throught the wrong hole so it turns with the pivot itself.

EDIT: Like this:

I'm not a fan of shielded tone-arm cables, as the metal tube of the tone arm itself acts as a shield, especially as it's directly grounded through a wire. All the arms I've rewired have been with four very thin flexible wires, carefully arranged round the pivots. You can check whether the arm cables are too stiff by first put on the stylus guard (or remove the stylus), disconnect the anti-skate (or set it to zero) then balancing the arm so it has no downforce, and the arm swings free. It should swing freely horizontally and vertically, responding to a gentle puff of breath to the headshell, with no sticking anywhere on its travel. If it sticks anywhere, it could be a sticky bearing, but if it doesn't stick but moves sluggishly, the arm cables are too stiff. Applying a small amount of anti-skate should allow the arm to swing freely from inner to outer record diameters.

As to the spec on the Cardas cable, it doesn't seem to be the issue. Capacitance only adds a few pF on the length of the arm cabling, although resistance is a bit high, but not enough to trouble any cartridge, especially a moving magnet.

S.

 

[sergeauckland]

Once the wires have exited the tone arm, it doesn't much matter. But if you have the thickness shown in that picture running through the tonearm, and especially the pivot, then that is probably quite bad. Even in the arm it will be influencing the mass and resonances.

It matters if the interconnect cables to the phono stage have high capacitance, as that can kill the HF from a moving magnet cartridge and/or cause a peak in the response followed by a rapid drop. The external cables should be well screened, low capacitance, something like RG6, although then ideally capacitance should be adjusted at the phono stage input as with short low capacitance cables it might even be too low.

S.

 

[tonycollinet]

It matters if the interconnect cables to the phono stage have high capacitance, as that can kill the HF from a moving magnet cartridge and/or cause a peak in the response followed by a rapid drop. The external cables should be well screened, low capacitance, something like RG6, although then ideally capacitance should be adjusted at the phono stage input as with short low capacitance cables it might even be too low.

S.

I was referring mainly to the mechanical characteristics - but yes, capacitance is also an issue.

 

[JaccoW]

Thank you gentlemen. I have something to look at this evening. Time to recheck the mechanicals of the new wiring.

Updates soon.

 

[Elkerton]

If the height of the pivot of the tonearm is too low, so that the arm is not parallel to the record surface, the playback sound will be dull. Conversely, if it is too high, the sound will be bright.

Good luck at sourcing and correcting your problem. BTW, nice restoration!

 

[JaccoW]

Sigh, I'm going to step away from this for a few days.

I spent most of my evening last night trying to repair it and at one point I had good sound from the left speaker but not the right one... and then after some fiddling not anymore. Oh and several blown fuses. One even after not having it on for an hour so there is clearly something deeply wrong with the current wiring. Or the soldering/desoldering has damaged the connectors in some way.

Some close-ups:

 

[tonycollinet]

I think those wires attached to your tone arm are way to thick.

And if you are blowing fuses, it suggests a short from mains to earth or live to neutral. Continuing without finding that is a very bad idea.

Possibly a stray strand of copper near one of the (I have to say it) fairly messy soldered joints.

 

[JaccoW]

I think those wires attached to your tone arm are way to thick.

And if you are blowing fuses, it suggests a short from mains to earth or live to neutral. Continuing without finding that is a very bad idea.

Possibly a stray strand of copper near one of the (I have to say it) fairly messy soldered joints.

You are probably right. And I know the solder joints are messy. I have learned a while ago I suck at desoldering and I have had to desolder these several times now. There is a reason why I did not even try my hand at my reel-to-reel.

I will probably order new connectors and cable and try again. You cannot break something that's already broken right?

 

[JaccoW]

So in the end I managed to fix the problem of blowing fuses but never managed to have it sound right again. I did realize that maybe I should try this with actual phono cables instead of regular RCA but whatever.

Instead I found a fully functional Technics SL-1400 automatic turntable and have been enjoying it (and the auto-return functionality) immensely, even more so with a Audio-Technica VM540ML cartridge. The Lenco is going on the backburner for now as a project.

Isonoe feet are on their way.