Technics SL1200mk2 - hum in left channel issue

I have a Technics SL1200mk2 with a Shure M97xE cartridge which always worked fine. But recently after replacing the old RCA cables, I noticed a ground/hum noise which only occurs in the left channel. It isn't a very loud noise, but hearable after cranking the volume up. Before the cable replacement the left channel side was perfectly silent. The noise is also hearable when the turntable is powered off.

Things i've tried, but unfortunately didn't resolve the problem:

• Tried different RCA cables, and even put back the old cable again
• Applied fresh solder on the five contacts on the RCA board
• Replaced the RCA board with a new one
  
• Internal grounding
• Cleaned the headshell contacts
• Checked the wires inside the tonearm
• Connected to a different amp

Any suggestions?

 

Try a different cartridge.
The cart was the only common gear during all your tries.

Best regards

 

Thanks! I will try this

 

Maybe also good to mention: When the turntable worked fine, the turntable was fitted with a red Monster RCA cable. When that cable broke, I replaced it with a Technics HiFi Interlink cable. And from then on the hum appears.

 

I'd for sure use the m5g cables which you can get from Kevin at KAB USA. Since it is coming from the left channel - try switching the cart wires on the cart so that L becomes Right - if it is the cart then I'd expect the right channel to have the hum - while if it is your wiring - I'd expect the left to still have the hum.

Just a thought.

 

Yes, I've changed the cart wires. And there was still a hum on the left.
But, maybe I've found the solution: When my SL1200 was working fine, the RCA cables fitted in where double shielded. These new RCAs from Technics are not double shielded.

To be continued...

 

Did you try switching the left and right RCA plugs on the new cables nearest the TT? (Source end) I think you maybe picking up an induced voltage from a nearby power cord or something generating an RFI that is being induced into the IC that is used for the left channel of the lesser shielded new cables.

 

Based on your opening post I figured you had done everything. You might as well re-wire the arm with quality wire now that you are in there - KAB has a kit for that along with an internal arm wand insert.

 

Yes, you're right! But if I remember correctly, I forgot to resolder the extra shielding properly

 

Okay, so I've finally bought a good quality RCA cable with double shielding, soldered it properly. And.... the hum is gone!

 

As soon as you do it properly, it works!


I have an unmodfied never repaired MKII, too. There's no hum or other electrics problems at all.

So, I guess, at the Technics factory, they already constructed and made everything fine to work without issues. I don't see no reason to replace cables for merely they are old, if there's no other severe reason like cable break. I guess, I also have the low capacitance version of the cables, so really no need for exchange.

Best regards