Technics ground loop problem?

[misterharrison]

Hi all

I'd appreciate some help trying to isolate and solve a ground loop problem I'm having with my Technics setup.

Setup:
Technics SL1210 mk2 with original TimeStep PSU, Mike New bearing, Isonoes
SME 309 arm with AT-33PTGII, Audio Origami tone arm cable
Ayre P-5Xe phono stage

Problem:
With everything connected and switched on, I'm getting a pronounced 50Hz (and associated harmonics) hum. When I unplug the TimeStep PSU, the hum disappears and I get the inky black silence that the Ayre phono is known for. So it looks like there's some kind of ground loop going on. I also got the same hum when I borrowed a friend's Whest Ps30RDT to see if it was a problem with the Ayre. Weirdly, with my old phono stage (Lehmann Black Cube) I get no ground hum at all.

Ideas:

Is this a TimeStep PSU problem? It is one of the original ones, so maybe there were issues with the early ones?

Alternatively, and I think this is more likely, there's something going on in the Technics as, for there to be a loop, there must be an unwanted electrical connection between the motor electronics and the tone arm. I also have vague memories of there being some kind of omission from the original TimeStep PSU installation instructions to do with disconnecting a ground lead from the Technics pitch fader. I don't remember doing anything like this when I installed the PSU, but it was quite a while ago.

Does anyone have any suggestions? I really want to get this sorted!

[CageyH]

Have you earthed the arm board? When I fitted my Rega arm, I made sure the arm. Oars was earthed. But I still had an earth loop. I then earthed the main PCB directly to the phono stage (from the main earth point) and it fixed my issue.

[chris@panteg]

I used an original Timestep psu for about 2 years with my 1210 ,never had any problem with hum ?

I also have an SME 309 with AT33EV so very similar to your set up , one thing I did when fitting the 309 ,was connecting the pitch fader earth to the arm board ,never had any hum or earth issues with three different phono stages !

[misterharrison]

Chris, I think that's probably what I failed to do when I fitted the SME 309. Can you explain exactly what you did, or maybe point me in the direction of a thread/post/webpage that shows what to do?
Thanks

[misterharrison]

Have you earthed the arm board? When I fitted my Rega arm, I made sure the arm. Oars was earthed. But I still had an earth loop. I then earthed the main PCB directly to the phono stage (from the main earth point) and it fixed my issue.

By connecting the pitch fader to the armboard, as Chris suggests, would I be earthing the armboard? Regas don't run an earth to the phono stage like other arms I think, so I suspect earthing solutions are different for them? I like the idea of running a wire from the main earth point on the PCB to the phono stage though. I might give it a try later.

[chris@panteg]

Chris, I think that's probably what I failed to do when I fitted the SME 309. Can you explain exactly what you did, or maybe point me in the direction of a thread/post/webpage that shows what to do?
Thanks

Yes certainly , I did do a photo guide on here somewhere ?

You will have to dismantle the deck , taking the rubber base off + the pocan inner base ,find the pitch earth wire ,it does have a tag .

Unscrew one of the nuts holding the arm board in place ,attach ,then put back in place , reassemble and job done .

I did ask Richard Peachey (vantage audio) about its importance and he said yes it should be fitted to the arm board .

[chris@panteg]

Found a photo I did .

http://i636.photobucket.com/albums/uu82/chrispanteg30/Armtransplant010.jpg

[CageyH]

By connecting the pitch fader to the armboard, as Chris suggests, would I be earthing the armboard? Regas don't run an earth to the phono stage like other arms I think, so I suspect earthing solutions are different for them? I like the idea of running a wire from the main earth point on the PCB to the phono stage though. I might give it a try later.

My Rega arm has an earth wire - it might be part of the AO modification, but basically as pictured, an earth wire from the arm board to pitch fader, and if that does not work, the PCB should do the trick.

[misterharrison]

Thanks, Chris. In the photo, it looks like there are two wires running from the armboard? If so, where does the other one go?

[chris@panteg]

Thanks, Chris. In the photo, it looks like there are two wires running from the armboard? If so, where does the other one go?

No its just one wire!

Might be a bit of loose wire? It was 4 years ago now.

[misterharrison]

Well that didn't work.

I just spent the afternoon taking the Technics apart and connecting a wire from the pitch assembly to the armboard, as shown in Chris' picture. While I was at it I also attached the extra earth lead on the AO tone arm cable to the same spot, creating what i thought was a seamless ground connection from the Technics to the phono stage.

But it hasn't changed the 50Hz hum at all.

I'm fresh out of ideas now, apart from the other idea of running a wire from the Technics main earth point on the main PCB. I guess that's next...

[chris@panteg]

Very strange? You say with Lehmann phono stage there was no hum
.

[Stratmangler]

Very strange? You say with Lehmann phono stage there was no hum
.

Probably floating earth - no physical earth at all.
I reckon the Ayre and the Whest both have physically connected earths, which is why the problem manifests itself with these phono stages.

Lifting (diconnecting) the mains ground on the Timestep PSU might sort things out.
Similarly lifting the mains ground on the phono stage might also do it.
It does very much sound like a ground loop issue.

[misterharrison]

That sounds like an option, if potentially dangerous?
How do I go about it?

[chris@panteg]

Might be a good idea to seek professional advice on this?

[misterharrison]

I thought that was what I was doing here...? ;)

[chris@panteg]

Well I'm only a rank amateur as my old dad used to say :lol:

I mean someone like Paul (rfc) or Guy (puresound) just a thought though it it still might be a simple fix .

I have a Vantage Audio psu which is earthed , the SME 309 is earthed at the Puresound T10 SUT , I have an optional earth lead to attach to my Marantz Pearl Lite from the T10 but found this was not needed so left it out .

The Marantz Pearl Lite is double insulated so no earth at the mains .

I have no hum or noise issues !

[CageyH]

I would try earthing the main PCB first before thinking about floating earths.
It's simple to do.

[misterharrison]

Yup I'm going to try that tonight when I get home. Just run a wire from that post at the bottom left of the main PCB to the earth post on the phono preamp, right?

[CageyH]

That's what I did.
It fixed my problem. If it does not work, you then need to find your dodgy earth.

[twotone]

I get a bit of hum if my earth cable goes near mains cables, I have a three wire tonearm cable one of which is an earth cable, I just move it away from the other cables and the hum stops.

The hum could drive you mad though.

[Mike_New]

I have come to this thread a bit late in the day.
However I will re-state what I have done so many times, where have you attached the 0V wire from the Time Step power supply?
It should be at the bottom LH corner
This problem has been covered extensively on this forum but as late as a few weeks ago I got an email from a user in NZ saying that the TimeStep instructions still say to attach the 0V line to the top RH screw. This is wrong electrically.

[misterharrison]

Well I've tried moving all my cables around and moving the PSU away from the phono in case the transformer was interfering in some way.

And Mike, yes, I moved the 0V connection to the bottom left ages ago, based on advice from the wise men of this very forum.

Going to try running a wire from the same bottom left 0V point to the phono's earth post tonight. Fingers crossed...

[misterharrison]

Brilliant! That worked!
Thanks, Kevin. The Ayre is now sounding glorious!

[CageyH]

Glad you have it fixed!
It took me a while to track down when I had my issue.