Sony PS-LX520 Turntable - Weak Left Signal & Intermittent Skipping

[deadevil13]

I hope this is the right place to post... also this is a copy of my original posting on AVForums

Hi

I have just brought second-hand a 1985 Sony PS-LX520 Fully Automatic Stereo turntable for £29.00.

I brought it to replace a pretty defunct 90s cheap Pioneer turntable.

Now I have it hooked up to a 1984(?) JVC A-K11 Stereo Integrated Amplifier (phono stage of course!) and that is then hooked up to the original JVC S-40 speakers.

I have run into a few problems with my new toy sadly

The first was when I plugged it in I had a terrible hum from the left channel (RCA white).... but by grounding the wire to the amplifiers metal casing that has now gone.

But now I'm left with little to no, left channel. As I have demonstrated in the clip shown below.


(http://www.youtube.com/watch?v=CLk5wZD8tUw)

I'm using the cartridge supplied (Sony ND300G). I have no clue how old this is. It looks 'okay', as in the needles not snapped off!

Anyway, the other problem seems to also be with ANY record (I have tried 5, various ages, conditions, and sizes) we get about a few minutes and then blip-blip-blip-blip .

I don't know much about audio equipment, and have started reading quite in depth guides about 'continuity' testing....

Do any of you think its just the cartridge that's being the weak link here? Or do you think its something more, serious?

Any extra information can be given

(Oh I'm 99% certain its not the Phono stage on the amplifier as it was working dual-channel with the last turntable I had)

[Edit]

I've just had a little play around inside of the turntable. I opened it up, and looked around for where the RCA cables come in. They go onto a small PCB which I have posted pictures below:

The solder to me looks fine. I tried a continuity test but I wasn't sure what I was doing...

[Luke122]

If you swap the left and right output from the table, does the issue follow the white RCA cable (ie plug it into the right input on the amp)?

I would continuity test the the leads from coming from the cartridge. Find where they reach the PCB inside the table, and test to see if the signal is actually reaching there from the cartridge. Maybe compare the left and right resistances from the cartridge leads to the pcb end as well.

It's possible that the cartridge is just broken/damaged/worn-out. If the needle is too worn, it wont stay in the groove, and it's possible also that the signal coming from it is the weak link here.. if it's damaged, it might not be sending all/some of the signal down the line.

[Konrad]

Second hand equipment, a quarter-century old ... it could have all sorts of hardware failures.

Your problem might as simple as a signal impedance mismatch between the turntable and your amp, which could be corrected with an inexpensive matching transformer. Output and input specifications should be written somewhere (usually on the back panel somewhere near the connectors) on each device. I'm not sure if chassis-grounding one of the output leads is a proper repair since the device could be built with floating grounds ... mid-80s mass-produced electronics, anything is possible.

I'd use an electrical contact cleaner on all the audio connectors, check all the internal wiring/traces and connectors for continuity, measure power supply voltages, carefully examine all the electrolytics. Plan on grabbing your soldering iron and DMM because you might need to systematically test and replace some or all of the big caps, lol. The usual troubleshooting - visual inspection, smell, feel for heat ... you might see or smell a burned resistor or some other defective component. I notice large ugly hand-soldered blobs in your pics, so you should probably check all the solder points. Hopefully none of the ICs or motors is cooked, since they might be proprietary or discontinued parts.

Basic audio-electronic test equipment should be able to diagnose stages and modules. I'm assuming your amp is operating properly and sounds fine with other audio equipment, you don't want to fix the wrong device.

You might still have the option of talking with the previous owner(s), at least if you approach diplomatically and make it clear you aren't demanding a refund on your £29.00. If you learn, for example, that the device has been sitting unpowered in storage for 15 years then it's a fair bet that the electrolytics are shot. Ask when the unit was last used, how it sounded, if it was ever repaired before, and whether it's ever been dropped or plugged into bad power sources, etc.

I hope this link helps. I haven't seen a vinyl turntable forever but I recall many times the problems would be in the needle, specifically in the needletip itself or in the needle armature parts which move, where fatigue would eventually snap fine-gauge braided copper wiring; replace full wire lengths, avoid cutting and splicing.

[deadevil13]

Hi - sorry about the slow reply.

I found out the issue regarding the audio - it needs a new cartridge. Some continuity testings turns a null result on two pins (its a P-Mount cart); which is the left audio. I am in the process of getting a new one to fit.

Regarding the skipping - its a common issue apparently with all Linear tracking turntables of this age. I did a bit of research and found out that my table works like so:
- A motor connected to a small controller board, outputs small bursts of motion
- This then turns a belt
- Which then turns another cog
- Which then rotates another cog with teeth
- Which is then connected via string
- Which then moves the tone arm back and forth.

With the bottom off, and the vinyl balanced above the table and using a torch (flashlight) I was able to see the mechanical workings. The motor works for a bit, and then intermittently just stops, or can't get a grip on the small rubber band.

I found that pressing the motor body back up into the case, starts it off again and the tone arm advances and plays properly again until it once again stops.

I don't have any rubber bands that are small enough at home, but I took it off and then put it back on and its had minor effect - but we still get stuck a bit. I taped the motor tightly back to the chassis to stop any wobble.

I still need to do some more testing. I have the service manual on my computer, which lists all the parts. I hope its just a case that it will need a new band - as if its a new motor I'll just get rid of it.

I brought it secondhand from Cash Converters (UK pawn shop chain) - so I can't find out when it was last used/how long it was stored for. I have 60 days to return it - which I will do if it turns out I can't get the tone-arm advancing properly.

[Konrad]

Old VCRs are full of motors and belts and all manner of wonderful mechanical cogs and gizmos, one might be a good source of salvage. Many service manuals call for intermittent replacement of rubber parts. Every component should have some sort of part number markings on it, or at least be documented in the service manual. You'll probably also find that the base mechanical stuff is somewhat generic and used in many models, it's mostly the electronics and cosmetic components which get changed on newer products.

There are also commercial chemical products which promise to rejuvenate rubber in various ways, though I'm not really sure what works or how well.