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Sony PS-LX520 Tonearm Drops Too Fast

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Sony PS-LX520 Tonearm Drops Too Fast

Postby mporta » 09 Oct 2013 23:02

Just received this as a project-got it working with the tonearm drive-belt replacement. When it auto starts, or even when manually lowering tonearm on disk, it drops FAST, and pretty harshly. My question is is this normal? Any way to adjust it? Thanks for any replies.
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Re: Sony PS-LX520 Tonearm Drops Too Fast

Postby ATHERMOS » 10 Oct 2013 19:58

We do not have the service manual for this TT as of yet in the library, but from the looks it seems that that the tone arm descent is controlled electronically, the descent rate is monitored by a feedback coil wound in a bifilar fashion (along with the actuating coil). So the entire feedback and the motor (actuating) circuit needs to be checked.
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Re: Sony PS-LX520 Tonearm Drops Too Fast

Postby mporta » 10 Oct 2013 21:22

Thanks so much ATHERMOS. Sounds a bit too much for me. Am I correct to assume that there is no damping fluid that may need to be replaced? I ask because I've been digging deeper into this issue, and it seems it's a common problem with older TT's. This thing is fully automated-lots of electronics to (potentially) mess up!! I don't want to toy with the tonearm electronics if I don't need to. Thanks again ATHERMOS.
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Re: Sony PS-LX520 Tonearm Drops Too Fast

Postby ATHERMOS » 11 Oct 2013 09:33

No, this TT is far too advanced, no damping fluid. You would have to find out whether the inputs of the sensor coil goes to a microprocessor (possibly not) or more likely, to an opamp based circuit and check for the correct functioning of the associated components. Do open it up and take a look, there might be presets for adjustments too.
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Re: Sony PS-LX520 Tonearm Drops Too Fast

Postby fscl » 11 Oct 2013 17:55

Welcome to VE...... :)

Though not in the VE library, the service manual can be found elsewhere on the net..... :) Atrmos clued me in on the actual tt in question, I was looking at the LX52 service manual to try and answer.... :oops: #-o

Though not called a BioTracer arm, it appears this unit and others at the time were precursors to the "official" BioTracer line of tonearms. Up and down cueing is performed by a linear electronically controlled motor (coil). As this tt has standardized on a T4P / P-Mount cartridge, the motor was sized / designed to raise and lower cartridges which standardized in weight and VTF specifications.

The drive coil is functioning correctly :-k since your unit has the ability to raise and lower the tonearm. What I do think is happening, as the cue down speed is too fast, is the anticipated weight of the cartridge / needle / VTF is not within the range of the tonearm coil motor design...... :-k :-k

There is a service manual on the Sony PS-LX55 here in the VE library which can be used as reference if you cannot get a hold of LX520 service manual.

Do you have a VTF scale which you can check the VTF? Do you have a scale to check the weight of the cartridge and stylus? The cartridge and stylus as a unit should weigh in at 6Gr per T4P specification..... :-k

Based on experience with my X555es, I had a Pickering XV-15 / 625E with brush installed on the tt. I like to set the tonearm up w/o the brush and then snap it on in lieu of balancing the entire assembly (cartridge + brush) and then adding 1Gr to the VTF. In theory this is 6 or half a dozen, however, the tonearm did not see / sense it this way. With the tonearm set w/o the dust brush, the cue rate down was "too fast". I have since installed a regualar 1/2 cartridge (Signet :) ) balanced the tonearm, dialed in the VTF and she cues beautifully...... :D =D>

What cartridge are you using? Does your T4P / P-Mount have a brush...... :-k :-k

From the LX520 service manual, there doesn't seem to be any adjustable pots to increase the force on the vertical coil slowing down the rate of decent. There is a weight in the tonearm which perhaps is 1.25Gr (spec'ed T4P VTF) .... :?: :-k has this weight shifted from rough handling / glue drying out....... :-k

I'll PM the location of the LX520 service manual.

Good luck.

Fred
Music is Everything....Except Predictable....WFUV Fan.
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Re: Sony PS-LX520 Tonearm Drops Too Fast

Postby mporta » 11 Oct 2013 21:46

Hello Fred,
Thanks for the welcome and the reply/PM. The Cart/Stylus is Ortofon OMP 5E, no brush (6g per Ortofon site). No VTF scale. I do see the 2 weights in the diagrams. It's quite possible that one or both came loose, as my boss gave this to me. When he brought it into the office, he was carrying it under his arm, like a book. I had specifically asked him to carefully place the TT in back of car on flat surface. Who knows where/how it has been stored for the past 15-20 years. Oh well, beggars can't be choosers, I guess! It was free. I want to upgrade to a Ortofon OM20 stylus, but not until I figure this out. Thanks again for your help. I'll let you know how it goes. Have a great weekend!!

Mark
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Re: Sony PS-LX520 Tonearm Drops Too Fast

Postby fscl » 11 Oct 2013 22:29

Thanks to jeepo65's contribution, there's a better service manual right in the VE library..... =D> =D> :) It's a lot clearer than the one from the other site.

This looks really simple, the first thing to check is page 10 of 25, I'm pretty sure the weight adjustment set screw is loose causing the adjustable weight to be full forward towards the stylus which may be the source of the added weight........ :-k :-k I'd venture to say that there are lines in the side of the short square tonearm section which have gradations for 1-->1.25-->1.5Gr.......:-k:-k:-k Set the screw to the 1.25Gr line and see how she cues.

Hopefully, it will cue / work correctly..... :)

Fred
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Re: Sony PS-LX520 Tonearm Drops Too Fast

Postby mporta » 21 Oct 2013 15:14

I had a chance to finally take a look at the TT, and there is no tonearm set screw present. I took the tonearm cover off hoping against hope that perhaps it was hidden inside there. No luck. At this point, I'm beginning to believe that it is something in the circuitry. I have yet to watch the tonearm actually go through it's motions with the cover off. I'll see if maybe something appears out of sorts when initiating tonearm drop. Thanks for everyone's help here. Any thoughts from anyone on whether it is advisable to proceed with a new stylus even though this situation may not be resolved? The LPs I'm playing are not in the greatest shape, but I would not be against purchasing some new LPs to hear what a new pressing sounds like with a new stylus. I got $11.00 sunk into this TT, the new stylus will run approx. 100.00, or I could go get what I originally wanted to get: a used AR XA or XB from Craigslist for approx 150.00. Thanks again!

Mark
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Re: Sony PS-LX520 Tonearm Drops Too Fast

Postby ATHERMOS » 22 Oct 2013 21:26

Is the arm holding up properly ? There is a spring to hold it up, find it in the exploded view of the tonearm in the service manual. Advance the arm electronically and then depress it to check the spring reaction, now if the arm drops very suddenly on the record electronically, it means that the feedback is not working. All the connections to the coil and to the PCB must be checked. Usually the semiconductors do not go wrong. Think and check logically.
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Re: Sony PS-LX520 Tonearm Drops Too Fast

Postby mporta » 23 Oct 2013 15:31

Well, it turns out taking a look at things moving with the cover off really helped :oops: It seems the stylus height adjustment screw was backed out too far. This was causing the adjustment plate (part #2 on page 10) to fall too low in the "groove of the photo interrupter". [-X When the coil passed through the magnet, the arm stuck momentarily, then suddenly released itself (not sure if gravity release or magnetic release), too late to catch up with the other moving parts. With some manual, hand operation, I could see/feel that the adjustment plate was "sticking". By lowering the stylus height (and thus the tonearm height), the adjustment plate was raised past the stick point. The tonearm now begins to descend at the same time the coil begins to move past magnet. =D>

Now the hard part: spend some money on a new stylus, or go get the AR I really want. I am required to tip toe around this TT when in operation, and the softest tap on the floor, plinth or base is audible. Perhaps another thread is in order! :?:

Thanks again for all the help everyone! It's much appreciated. Analog rules!!

Mark
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