Dual CS505 deck earthing. - UK Vintage Radio Repair and Restoration Discussion Forum

Mike Phelan · 2nd May 2006, 8:50 am

Hi folks
Don't go to any trouble here, but if you could tell me if the arm is earthed, that would be useful for me.

The tale is:
CS-505-2 worked fine - next time I used it, there was a fair amount of hum on both channels and volume was a bit low. Unplug headshell, hum goes. Checked connections on cartridge, and earth from deck to Quad 34 earth connection - OK, but arm does not seem to be earthed.

AFAIK, they usually are!

Swapped Ortofon cartridge with Shure M75 (thanks to Paul Sherwin). Worked OK for a while, then hum slowly increased and volume decreased. As soon as I touch the arm or turntable (which seems to be isolated) I get a little spark (from nylon carpet?), the volume comes up and the hum goes, for another 10 minutes or so!
Very weird, so I was wondering if there was some strange static effect. I am not stuck for finding the problem yet; I will be removing the deck when I have diagnosed it further, but for now, I have found that the motor, spindle and deck plate are all earthed, and the arm is not.

peter_sol · 2nd May 2006, 2:14 pm

Hello

The moulded on phono plugs on these tend to go high resistance so it is best to cut them off and fit new ones,also the cartridge sometimes goes o/c on one or both channels so check this normal resistance around 5t0 600ohms is normal.

Hope this helps

Regards

Peter.

valveaudio · 2nd May 2006, 5:45 pm

Mike
I have a CS505-4 and I just checked the arm.
You have to be a little careful where you measure, the headshell is plastic and the coating on the arm itself is non-conductive but you should find that the the headshell retainer (the aluminium bit) is earthed via a small collar.
Hope this is helpful.

Trevor

2nd May 2006, 8:50 am	#1
Mike Phelan Dekatron Join Date: Nov 2003 Location: Near Leeds, West Yorkshire, UK Posts: 4,609	Dual CS505 deck earthing. Hi folks Don't go to any trouble here, but if you could tell me if the arm is earthed, that would be useful for me. The tale is: CS-505-2 worked fine - next time I used it, there was a fair amount of hum on both channels and volume was a bit low. Unplug headshell, hum goes. Checked connections on cartridge, and earth from deck to Quad 34 earth connection - OK, but arm does not seem to be earthed. AFAIK, they usually are! Swapped Ortofon cartridge with Shure M75 (thanks to Paul Sherwin). Worked OK for a while, then hum slowly increased and volume decreased. As soon as I touch the arm or turntable (which seems to be isolated) I get a little spark (from nylon carpet?), the volume comes up and the hum goes, for another 10 minutes or so! Very weird, so I was wondering if there was some strange static effect. I am not stuck for finding the problem yet; I will be removing the deck when I have diagnosed it further, but for now, I have found that the motor, spindle and deck plate are all earthed, and the arm is not. __________________ Mike.

2nd May 2006, 2:14 pm	#2
peter_sol Octode Join Date: Aug 2003 Location: Welwyn Garden City, Herts. UK. Posts: 1,906	Re: Anybody got a Dual CS505 deck and a meter handy? Hello The moulded on phono plugs on these tend to go high resistance so it is best to cut them off and fit new ones,also the cartridge sometimes goes o/c on one or both channels so check this normal resistance around 5t0 600ohms is normal. Hope this helps Regards Peter.

2nd May 2006, 5:45 pm	#3
valveaudio Hexode Join Date: Feb 2006 Location: Diss, Norfolk, UK. Posts: 386	Re: Anybody got a Dual CS505 deck and a meter handy? Mike I have a CS505-4 and I just checked the arm. You have to be a little careful where you measure, the headshell is plastic and the coating on the arm itself is non-conductive but you should find that the the headshell retainer (the aluminium bit) is earthed via a small collar. Hope this is helpful. Trevor