simon3142 Posted August 1, 2012 Share Posted August 1, 2012 I wonder if anyone can help with a hum problem on an early 60s SG special with P90 pickups. I am not sure if this is the best place for this question, if there is a better place I would be happy to move. The problem is recent and I first noticed it after swapping the bridge. It was an uncompensated wrap around bridge that just slides into the mounting posts. I tried out a cheap “pattern” compensated bridge but I didn't like the result and swapped the original back immediately. There was no unscrewing or disconnections involved so I don't see how this could be related unless the wiring got shaken up although I didn't touch it. The guitar has two types of hum 1) a low level mains hum which goes away with the pickup selector in the central position – as expected. 2) A much louder buzzy hum which is stays even with the pickup selector central. This is the one that is bothering me. The hum goes away if I touch the strings or any earthed part of the wiring such as the back of a pot or screening braid. It gets louder if I touch the insulation on the "live" wire from a pickup. The hum is affected by the volume controls in an odd way. It reaches a peak at about ¾ volume and then its becomes more buzzy or treble as though the volume is partially acting as a tone control. The wiring is original apart from an earth wire to the socket which fell off and I connected it to the earth on the switch long before this problem started. There is no problem with another guitar (strat) using the same same cable and amp. Link to comment Share on other sites More sharing options...
retrorod Posted August 2, 2012 Share Posted August 2, 2012 You should have a ground wire from the controls to the treble-side anchor post insert. Perhaps it got 'loosened' somewhere in your bridge replacement process. A cheap 'continuity tester' multimeter would help in finding the broken ground. Hope you get it! Link to comment Share on other sites More sharing options...
simon3142 Posted August 2, 2012 Author Share Posted August 2, 2012 You should have a ground wire from the controls to the treble-side anchor post insert. Perhaps it got 'loosened' somewhere in your bridge replacement process. A cheap 'continuity tester' multimeter would help in finding the broken ground. Hope you get it! Thanks for replying I did find what I assume is the ground wire from the post hidden under the pickup leads - hard to spot without good light. There is continuity between the bridge and ground in the cavity and touching ground anywhere in the cavity stops the hum and I have tried using a crocodile lead to connect the bridge to ground in the cavity with out effect. The resistance between the bridge and ground in the cavity is around 0.5 ohms - hard to tell exactly as the meter is no very accurate, but it is slightly higher than shorting the probe directly. I am not sure if that is a problem but I suspect not as touching ground in the cavity works. It has turned into a real puzzle and for the time being I think I am defeated. :-) I did repost this query on the repairs forum which I think might have been a better place. Link to comment Share on other sites More sharing options...
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