I’m rewiring a Grace 940 tonearm that I bought on ebay. I’ve owned a couple of these arms and have a small supply of spare parts. In examining the Grace, I found that one of the signal wires (green) was not attached at the headshell end. For reference, the input (headshell) end of the tonearm contains a plastic, cylindrical terminal block with four spring loaded soldering/connection posts. The output (interconnect) end contains a similar terminal (DIN) block with five terminals: four signal (+/-) wires plus two black ground wires on the fifth terminal. Unfortunately, the headshell terminal block was stuck in the arm tube would not budge, and I ended up having to drill it out. (Got a spare.)
One of the two ground wires that was attached to the output terminal block is still visibly attached to a bolt that holds the upper part of the tonearm to the lower support shaft. However, the second ground wire which runs from the output, through the pivot assembly, toward the input terminal, is now unattached. Because I destroyed the input terminal block, I cannot determine how that wire was attached. My assumption is that that ground wire’s purpose is to ground the cartridge; and it was previously attached to one of the two (-) ground cartridge connectors. If so, my plan would be connect the dangling black, ground wire to one of the two negative soldering terminals on the input terminal block.
Does that sound correct?
Thanks,
One of the two ground wires that was attached to the output terminal block is still visibly attached to a bolt that holds the upper part of the tonearm to the lower support shaft. However, the second ground wire which runs from the output, through the pivot assembly, toward the input terminal, is now unattached. Because I destroyed the input terminal block, I cannot determine how that wire was attached. My assumption is that that ground wire’s purpose is to ground the cartridge; and it was previously attached to one of the two (-) ground cartridge connectors. If so, my plan would be connect the dangling black, ground wire to one of the two negative soldering terminals on the input terminal block.
Does that sound correct?
Thanks,
Probably not..
The cartridge grounds on the block should be blue and green if the standard color scheme is in use. Might there be another internal connection to make sure the something else was properly grounded?
In any event you would not want a shared cartridge and arm ground at a point in the arm where they cannot be separated if needed.
The cartridge grounds on the block should be blue and green if the standard color scheme is in use. Might there be another internal connection to make sure the something else was properly grounded?
In any event you would not want a shared cartridge and arm ground at a point in the arm where they cannot be separated if needed.
Think I wasn't clear. The DIN block contains five posts and six wires: red, white blue, green, 2-black joined. The four signal wires plus one of the black wires run all the way to the input terminal block area. The remaining black wire is attached to the vertical post under the pivot mechanism. Also, the loose black wire is the same length as the other four and there is no visible connection in the input area.
If I understand you correctly it's probably connected to the arm tube at the block (SME connector) somehow? By input terminal block I assume you mean the SME connector at the business end of the tone arm. (Head shell connector) At the other end I assume you mean the 5 pin din connector that the cable to the pre-amp plugs into.
Right!
Apologize for not knowing the proper term for front end connector. Seems certain that the loose ground wire was connected to or around the SME connector and needs to be reconnected. I don't want to experiment if it can be avoided. I can find no technical documentation on these Grace tonearms. My first thought was that the ground wire was soldered to the inside of the tonearm tube. But there is no physical evidence of that inside the tube, and, since the tonearm assembly is already grounded at the vertical mounting assembly, a second ground would be superfluous and possibly risky. All I can figure is that the cart is grounded via the green or blue to the DIN, through the interconnect, and on to the preamp ground.
Thanks for commenting.
It's not unusual to have several ground connections in order to avoid the issue with bearing assemblies which may or may not provide good grounding continuity.
It might have fit into a groove on the connector.
You might want to try asking at www.vinylengine.com - need to be a member to post and search library and database.
It might have fit into a groove on the connector.
You might want to try asking at www.vinylengine.com - need to be a member to post and search library and database.
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