Technical Help Please

[Leehallam]

Just set up my turntable an I have a terrible hum.

i have removed the cartridge an I have the same hum on quarter volume.

so I thought grounding/earth issue checked that all on checked earth continuity with a multi meter and it all looks good.

now this is where I need the help I have done a cables check with the multi meter to the pins and everything is fine but the red cable is matching up with the right pin but I also get continuity to the eath pin, is this wrong it feel wrong and as is I have a broken cable in the arm touching eath.

It is a roksan radius with nima arm.

any help please.

 

[drummerman]

I am not familiar with turntables/arms but post at http://www.diyaudio.com/forums/analogue-source/ and you should get some help.

regards

 

[andyjm]

Just set up my turntable an I have a terrible hum.

i have removed the cartridge an I have the same hum on quarter volume.

so I thought grounding/earth issue checked that all on checked earth continuity with a multi meter and it all looks good.

now this is where I need the help I have done a cables check with the multi meter to the pins and everything is fine but the red cable is matching up with the right pin but I also get continuity to the eath pin, is this wrong it feel wrong and as is I have a broken cable in the arm touching eath.

It is a roksan radius with nima arm.

any help please.

Firstly, you need to do all testing with the tone arm cables disconnected from the amp. Tone arm wiring usually has the four cartridge connections separate from an overall screening earth. Assuming RCA connectors, two of the cartridge connections go to the 'tips' of the RCA connectors, the other two to the 'body' of the RCA connectors.

The overall screening earth is bought out to a separate connection (more often than not a spade connector) which goes under a binding post on the amp.

There should be no connection between any of the 4 cartridge connections and the screening earth with the amp disconnected. If there is, you have a fault somewhere. You should also check continuity of the 4 cartridge connections to their respective RCA connectors.

The amp will probably internally connect the screening earth and the bodies of the two RCA plugs together, so the amp must be disconnected before you test.

Good luck.

 

[Leehallam]

Andyjm,

thanks for that.

i have removed the cartridge so I just have the 4 wires. I have removed the tone arrm it it on a 5 pin plug.

i put the multimeter on a continuity test and got the following results

white blue and green cable no problem signal on the correct pin on the plug nothing on Earth. On the red cable I have continuity to the correct pin on the plug but also continuity to eart pin. What does this suggest the fault is ?

Lee

 

[Leehallam]

Well i guess I need to oull the cables out of the tone arm to see if one is broken this looks like it is going to be a tough job.

or well here goes.

 

[Leehallam]

Well problem fixed.

i started to pull out the wires carefully and notice at the plug end the earth was touching the red cable. Straightened it out so it was not touching checked again with the multimeter and hey presto fixed. Put the cartridge back and and now listening to Simon and garfunkle it sounds sweet. Just waiting for the graham slew on home loan now and hopefully finished for a short while.

Lee