On 22/10/2018 23:46, Bill wrote:
Posting here just in the remote possibility that someone has one of
these turntables and can help.

A friend gave away all his vinyl LP's some time ago, having transferred
a lot to CD**.
He has now discovered a box of LP's and tried to connect up a turntable
to an amplifier. He rang me for help. I can't get to see him and it for
some time, and he has no multimeter or other test equipment.

It hums. I am trying to guess whether a missing earth or an earth loop
is the more likely problem. I assume and hope that both the amp and
turntable chassis are earthed. At this stage no other equipment is
connected and the amp is fine on its own. I am a bit reluctant to ask
him to try poking an earth around even if I thought he was capable.

The turntable + pickup arm are a Rega Systemdek 2X2. My question is
whether the pickup assembly is earthed to the turntable chassis or
should it pick up its earth via the phono connection to the amp?


ITYM Systemdek with a Rega arm? They usually used a Rega RB250 arm
(green blob on a black counterweight). IIRC the arm was earthed to the
chassis via the body - there is no trailing wire - and that in turn can
be connected to an earth screw at the back of the turntable.

I'd just work through by deduction starting with only the turntable
connected to the amplifier - connect a wire from the turntable earth to
the amp chassis's earth screw, a known earth if the amp isn't earthed,
and no connection.

--
Cheers, Rob

In message , RJH writes
ITYM Systemdek with a Rega arm? They usually used a Rega RB250 arm
(green blob on a black counterweight). IIRC the arm was earthed to the
chassis via the body - there is no trailing wire - and that in turn can
be connected to an earth screw at the back of the turntable.

I'd just work through by deduction starting with only the turntable
connected to the amplifier - connect a wire from the turntable earth to
the amp chassis's earth screw, a known earth if the amp isn't earthed,
and no connection.

Thanks, Rob. I have talked to him again and agreed that he will put it
all on hold until I can get out to visit and do some proper fault
finding. AIUI, the amp has been put away for quite a time and the
Systemdek for over a year, so it all needs to be looked at first from a
safety perspective before looking for the hum. The hum appears when he
plugs the phonos from the turntable into the amp - nothing else
connected, so, from your description, there may be an actual fault.

It was used in a different room with a different amp when it was
previously working.
--
Bill

---
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In article ,
Bill wrote:
Thanks, Rob. I have talked to him again and agreed that he will put it
all on hold until I can get out to visit and do some proper fault
finding. AIUI, the amp has been put away for quite a time and the
Systemdek for over a year, so it all needs to be looked at first from a
safety perspective before looking for the hum. The hum appears when he
plugs the phonos from the turntable into the amp - nothing else
connected, so, from your description, there may be an actual fault.

It will certainly hum if there is no ground connection to the chassis.
It's usual to have the cart grounds going direct to the amp, and not
connected to anything else.

--
*A bicycle can't stand alone because it's two tyred.*

Dave Plowman London SW
To e-mail, change noise into sound.

On 24/10/2018 11:15, Dave Plowman (News) wrote:
In article ,
Bill wrote:

Thanks, Rob. I have talked to him again and agreed that he will put it
all on hold until I can get out to visit and do some proper fault
finding. AIUI, the amp has been put away for quite a time and the
Systemdek for over a year, so it all needs to be looked at first from a
safety perspective before looking for the hum. The hum appears when he
plugs the phonos from the turntable into the amp - nothing else
connected, so, from your description, there may be an actual fault.

It will certainly hum if there is no ground connection to the chassis.
It's usual to have the cart grounds going direct to the amp, and not
connected to anything else.

The usual cause of hum on a classic record deck is a ground loop
somewhere or a completely missing signal earth. Connecting all of the
earths together is a fairly common mistake. The one to keep the chassis
becoming live should be separate to the sensitive signal earth shield.

I tried mine recently and confess that I had forgotten just how tetchy
they were about earthing, stray magnetic fields and acoustic feedback.

--
Regards,
Martin Brown

On Wednesday, 24 October 2018 10:48:13 UTC+1, Bill wrote:
In message , RJH writes

ITYM Systemdek with a Rega arm? They usually used a Rega RB250 arm
(green blob on a black counterweight). IIRC the arm was earthed to the
chassis via the body - there is no trailing wire - and that in turn can
be connected to an earth screw at the back of the turntable.

I'd just work through by deduction starting with only the turntable
connected to the amplifier - connect a wire from the turntable earth to
the amp chassis's earth screw, a known earth if the amp isn't earthed,
and no connection.

Thanks, Rob. I have talked to him again and agreed that he will put it
all on hold until I can get out to visit and do some proper fault
finding. AIUI, the amp has been put away for quite a time and the
Systemdek for over a year, so it all needs to be looked at first from a
safety perspective before looking for the hum. The hum appears when he
plugs the phonos from the turntable into the amp - nothing else
connected, so, from your description, there may be an actual fault.

unlikely.

In article ,
Martin Brown wrote:
It will certainly hum if there is no ground connection to the chassis.
It's usual to have the cart grounds going direct to the amp, and not
connected to anything else.

The usual cause of hum on a classic record deck is a ground loop
somewhere or a completely missing signal earth. Connecting all of the
earths together is a fairly common mistake. The one to keep the chassis
becoming live should be separate to the sensitive signal earth shield.

I tried mine recently and confess that I had forgotten just how tetchy
they were about earthing, stray magnetic fields and acoustic feedback.

Yes. But there are usually only a few options with a decent turntable. And
you won't break things by experimenting - just keep the volume set low
when doing so.

Well remember a 'separates' system a pal bought new many years ago - IIRC
Pioneer. Every part had a three core mains lead. Phono leads supplied too.
No matter what you connected to the amp, it hummed due to a ground loop.
I'd guess it was designed for two core earth leads, and converted for UK
etc sales.

--
*If God dropped acid, would he see people?

Dave Plowman London SW
To e-mail, change noise into sound.

On Wed, 24 Oct 2018 10:39:02 +0100, Bill wrote:

In message , RJH writes
ITYM Systemdek with a Rega arm? They usually used a Rega RB250 arm
(green blob on a black counterweight). IIRC the arm was earthed to the
chassis via the body - there is no trailing wire - and that in turn can
be connected to an earth screw at the back of the turntable.

I'd just work through by deduction starting with only the turntable
connected to the amplifier - connect a wire from the turntable earth to
the amp chassis's earth screw, a known earth if the amp isn't earthed,
and no connection.

Thanks, Rob. I have talked to him again and agreed that he will put it
all on hold until I can get out to visit and do some proper fault
finding. AIUI, the amp has been put away for quite a time and the
Systemdek for over a year, so it all needs to be looked at first from a
safety perspective before looking for the hum. The hum appears when he
plugs the phonos from the turntable into the amp - nothing else
connected, so, from your description, there may be an actual fault.

It was used in a different room with a different amp when it was
previously working.

There is also the possibility if the pickup is magnetic that it's
picking up hum from the field from a nearby transformer or motor.
--
Dave W