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Rega P3 24 Phono plug knackered?

Getting a lot of hum. Tried everything except unscrewing the sleeves which was mentioned I think earlier today on another thread about a P10. Thanks for taking the time to look appreciate it.
 
McKMini said:
Getting a lot of hum. Tried everything except unscrewing the sleeves which was mentioned I think earlier today on another thread about a P10. Thanks for taking the time to look appreciate it.
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Suggest getting hold of a digital multimeter with which to test continuity between headshell tags (cartridge disconnected) and RCA plugs.

In the meantime, it doesn't hurt to ensure that the tonearm cable is kept clear of power cables. Also, the deck itself shouldn't be positioned too close to other components with mains transformers within, nor near any wall wart type transformers. If you use a separate phono stage, it also helps to make sure that this is well away from its own wall wart, as well as clear of other mains powered devices, including the P3.
 
Both screens look very poorly soldered, with the left one cracked - shocking if this is on a commercially made product. I'd resolder them as a matter of course before going any further and I suspect you hum will go. A multimeter continuity check may not show this type of fault up as you will disturb the connections applying the probes!
 
McKMini said:
It tests fine for continuity with the blue wire so I guess the problem lies elsewhere! Thanks all.
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I neglected to mention that you can also test the integrity of the tonearm ground paths by placing your probes across tonearm metal end stub and RCA Lch -ve ring, as well as between either of the metal screw heads located below the VTF dial (arm carrier) and RCA Lch -ve ring.

The reason for testing both points on the arm is that both the arm tube and arm pillar metal are connected to Lch -ve at the cable harness terminals. Specifically, the arm tube via a wire running from a metal tag that acts a shim between end stub and tube, and the arm pillar via a metal strip that folds over the side of the plug (as per photo below) and is wedged between plastic plug and metal cylinder within upon insertion.

Should an aftermarket end stub and counterweight have been fitted at some point, the arm tube ground tag may have been dislocated. Same goes for the cable harness plug ground strip (and/or internal ground wire connection to same) should there have been a rewire, or this has been otherwise disturbed.

[image credit: struth of TAoS]
04e84b610b726a49e3048c0c74d250a0.jpg
 
Interestingly the bare metal end of the arm tested positive but the screws below the dial didn’t?
 
McKMini said:
Interestingly the bare metal end of the arm tested positive but the screws below the dial didn’t?
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The screws aren't the best place to test for arm pillar ground continuity, only IIANM the external part of the arm pillar isn't conductive on RB301 on.
 
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