Turntable Right Channel Dropping Out; Grounding Cartridge Body Brings It Back

@elliottbnewcombjr Thank you for responding. You may be on to something. I have tightened the tags (as I think they call them) and I did have a time soldering the new tonearm wires on. It seems some soldering flux wicked itself into the spring-loaded ‘pads’ the cartridge pins contact. The result is that one of the pins on right channel keeps sticking. Befote the stylus brush trick, I was removing the headshell and tapping the tonearm relentlessly before re-inserting the headshell. It usually did the trick for that session, but the issue always came back.
 

I have cleaned the ‘pad’ housing repeatedly with alcohol, and blown it out with air at 150 psi; but I’’m afraid to use anything stronger for fear of damaging the plastic. (My industrial grade contact cleaner warns against using it on plastic, as does the CRC brand contact cleaner available at the local Lowe’s Home Improvement.) I considered contact lubricant, but when I saw mineral oil as an ingredient, again I held off. Thought graphite dust used to lubricate locks might help, but I believe that stuff is very conductive and hard to keep from blowing everywhere. My latest purchase is brake cleaner containing carbon tetracloride— it doesn’t say anything about being a danger to plastics, and I know it cleans the heck out of gummed up typewriter keys. But, again, I’m a little leery of trying it as I fear it might be too strong. 
 

@lewm Thank you for responding. I do have another cartridge, an older Stanton 500 Mark II, but it is mounted in a different headshell. I am loath to uninstall either cartridge as it takes me so long to get the things aligned. I only recently learned that the overhang specified by the manufacturer was provably incorrect. I don’t have a protractor that allows me to confidently set the cartridge at both null points without moving the protractor itself for each null point. I’m considering the purchase of a SMARTracter made by Acoustical Systems, but is twice the price of the new cartridge. I can check my results with the oscilloscope and the test record. But it always seems to take me at least two tries and three hours I’m exhausted and don’t want to go near the turntable for a couple of days. 
 

But now that I’ve finally gotten them both dialed in, I could try swapping the Stanton cartridge in its headshell into the turntable that currently hosts The Vessel cartridge. I can testify that I’ve run The Vessel cartridge in the turntable that currently hosts the Stanton cartridge and it didn’t give me a single hiccup. Again, the troublesome turntable has balanced interconnect modification. The turntable with the original unbalanced interconnect hasn’t given me any problems. But then again, the turntable that received the balanced interconnect modification gave me fits with another Stanton 500 Mark II cartridge: there was a persistent 60 cycle (or 120 cycle) hum, which is why it was set aside to await a the new Vessel cartridge. And, if my records are correct, that is the cartridge I’m now using successfully; because my ‘good’ Stanton cartridge failed under testing. 
 

Yet, as you might glean from my account, there have been so many changes, I may have lost track of them all. It might help to ‘clean slate’ the whole project by removing both the balanced cables and ground switch so that both tables are as similar as possible and take it from there. I was fascinated by the concept of a balanced connection for any cartridge using four (4) pins, but in practical terms I haven’t realized any sonic benefit, and I’m not currently needing the extra length in any case. 

@richardbrand Thank you for responding. (I chuckled at your reply to Elliott Necomb above.) Yes, it certainly seems your electrical diagnosis is correct. The same thought has occurred to me. I’m going to have to remove The Vessel cartridge to verify, but I believe the top of the cartridge is plastic. The stylus insert’s exterior is plastic. The only metal part is under the black plastic on top and behind the red stylus plastic in front. The cartridge mounts with bolts and nuts, so there is no metal-to-metal contact at that point. 
 

So . . . I’m wondering if the metal portion is acting more as a shield than as a conductor; and that, as a shield, it needs a connection to ground. I would need to provide that connection, at least to the cartridge. 
 

The tonearm has a 5th black wire that provides the ground into the tube. That is to say, the wire is connected to ground at the same terminus as the grounding wire on the interconnect— the wire that runs back to the screw on the case of the phono stage. [Edit: The switch may interpose here, bringing 100 Ohm lift in and out of circuit, not sure, need to check, see more below.] At the ELAC phono stage I can choose betwen either a screw labeled ‘signal’ and one labeled ‘chassis’.  The other end of the black wire , as I said, disappears into the rear of the arm tube at the bearing end and does not appear at the connector at the cartridge end of the tube. My Ohm meter tells me the connection from the wire in the plinth to the front portion of the tube is good. I don’t think the front portion of the tube is electrically connected to the tonearm tower or bearing, see below. 
 
The shielding of the tonearm wires inside the plinth (if the term applies) is interesting. A short length (2-3”) of bare ‘woven’ shielding (the kind that resembles so-called Chinese handcuffs, in which tugging at the ends shrinks the cross-section, in the ‘handcuffs’ tightening down on each finger inserted into the ends) which is soldered to the same ground wire potential as the aforementioned ‘black wire’ above, and, at the other end, is secured to the tonearm tower. This coonection scheme, in my opinion allows the ‘shield’ to serve as both a shield and a conductor. Somewhere in there (I would have to open it up again), there is a 100 Ohm resistor that ‘lifts’ the signal ground from the chassis ground.  
 

I think I might need to investigate this aspect of the grounding. The purpose of the switch I added on my first go-round with this turntable was to allow me to switch from chassis to signal ground at the turntable and give myself the same choice at the turntable as I had at the phono stage. 
 

Finally, you are right about some cartridges using one of the pins for grounding. The ‘ground strap’ for the left channel (-) signal (blue wire) on the Stanton cartridge is exposed and labeled ‘GND’. The same (necessary) connection may be required by The Vessel, but the connection is hidden within the body. I guess I could break out my Ohm meter to investigate. 

@elliottbnewcombjr I like your heat sinking forceps. Very Andy for this type of work, in my opinion. 

@richardbrand 

that’s paying attention to the true meaning of things!

Or, is it the true nature of things?

@oldrooney 

https://www.amazon.com/MLTOOLS-Helping-Third-Soldering-Station/dp/B01961086E