Hum in right speaker becomes hum in both speakers when headshell detached

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Hi



I have an SME 309 tonearm and hum in my right speaker . When i detach my headshell the hum appears in both speakers . Ive cleaned the headshell pins both ends and headshell leads are snug

headshell leads are stock van der hull (they seem undamaged)

Changing the cartridge makes no difference

Ive disconnected all other appliances in house (Tvs , fridges , light dimmers)

My phonocable is XLR. Ive tried different brand phonocables makes no difference

My turntable is belt driven and the motor is away from cartridge . Touching the turntable or tonearm with my hands doesnt alter the hum

Hum in right speaker gets louder as I turn up volume . I live in australia - electricity supply is 10 amps/240 volts .
 
An externally hosted image should be here but it was not working when we last tested it.


this is what it looks like - the PSU has a three prong connector - whether the turntable/arm itself is grounded i dont know.

I tried to disassemble the SME tonearm but dont know how to : the cap on front seems very well attached (maybe i need to use more force)

An externally hosted image should be here but it was not working when we last tested it.


Ill buy a multimeter tommorow

i should state that i can hear music through both speakers , despite the Hum on the right

I have the motor/turntable about 60 cm away from my phonostage -moving the turntable further away makes no difference
 
Have you done a continuity check?

Ok just finished with my multimeter and i have continuity between red , white , green and blue headshell leads and their corresponding pins on the tonearm DIN plug

ive checked my XLR phonocable and it has continuity for signal and the ground lead ( im assuming everyone is using Pin 2 HOT , pin 3 return Pin 1 shield)


when i tested continuity of the turntable's earth : the ground pin on the DIN plug of the tonearm has continuity with everypart of the turntable Except there is no continuity between DIN ground pin and the actual magnesium shaft of the tonearm (excuse my ignorance of this is normal)
 
The SME arm and headshell are painted magnesium - ive just checked with multimeter...

No continuity between tonearm DIN plug ground pin and tonearm shaft

No continuity between tonearm DIN plug ground pin and tonearm headshell

Perfect continuity between tonearm DIN plug ground pin and headshell screw that secures headshell

i presume this is normal ?

I have no continuity between the cartridge body and the headshell - i presume because the headshell is painted ( i seem to recall a guy in the UK scraping the paint from his headshell to get rid of hum , cant be sure )

Also the transformer on the electricity pole up the road from my house makes the most awful loud buzzing noise . I presume this has nothing to do with my speaker hum

my pre amp , power amp and phonostage all have 3 prong IEC connectors
 
tonight i noticed : swapping the XLR phonocable right (red) cable into left phonostage input and left phonolead (white) plugged into right Phonostage input - hum stays in right speaker

put things back to normal -

Then swapped the XLR OUT CABLes from the phonostage to the preamp: the Hum has shifted to the Left speaker now

All my cables are working perfect on a continuity test
 
just bought 4 cheap XLR cables and lifted pins 1 on all of them

first, replacing xlr cables from phonostage to pre amp - hum remained in right speaker

Next replacing XLR cables from Phonostage to pre amp and preamp to power amp - hum still in right speaker

so i guess i gotta let the dealer technician troubleshoot, im at a loss to explain .

A few general questions:

1. do ground loop hums affect both speakers ? do ground loop hums get louder with the volume ?

2. whats it mean when u mute a pre amp or phonostage amp and when you un-mute you get a little popping noise throught the speaker (ive always had that and assumed it to be normal)
 
Simple: the hum is originated internally in the right channel of your phono stage. You need to open it and have a look, or ask help of a service technician having an oscilloscope.

The hum appears in both speakers when you detach the phono leads, because the hum picked up in both channels will be much stronger than the internally originated hum in one channel, so it masks it.
 
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