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Post by JohnH on Dec 10, 2005 15:44:46 GMT -5
Here is a wierd thing that has me scratching my head.
On my 3 SC Strat copy, the settings involving the neck have started to behave strangley - working but not sounding right. This is on my guitar with multiple series/parallel combos - see the ToneMonster2.
Investigating with a multimeter to check resistances (and never for a moment doubting my wiring design! - it was fine last week!) - I traced the problem to the neck pup itself. I pulled it right out of he guitar.
The resistance between hot and ground has become infinite, on all the settings of both my analogue and my digital meters. But I still get a sound signal from it, tapping with a screwdriver. It is as if the coil is broken, but some capacitive or inductive coupling between the parts keeps it able to make some signal although not quite as loud as normal.
Interestingly, the series settings were working OK, but the parallel ones were sounding almost the same as whatever other pups were in circuit, which makes sense with a neck pup with infinite resistance.
I opened up the pup - two ceramic bar magnets wedged into the plastic cover, with the 6 pole pieces sandwiched between. And here I am stuck, the thing is solidly jammed in, and I have no chance to get to the coil on the other side of the magnets and poles.
My questions are - Do we normally expect to be able to remove the covers from basic SC pups? - if so I might persist in trying
Any other theories or comments?
On the other hand, this may be my perfect excuse to fit a new set of vintage sounding alnicos...
John
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Post by UnklMickey on Dec 13, 2005 10:46:56 GMT -5
....The resistance between hot and ground has become infinite... ... It is as if the coil is broken, but some capacitive or inductive coupling between the parts keeps it able to make some signal although not quite as loud as normal. Interestingly, the series settings were working OK, but the parallel ones were sounding almost the same as whatever other pups were in circuit, which makes sense with a neck pup with infinite resistance. My questions are - Do we normally expect to be able to remove the covers from basic SC pups? - if so I might persist in trying On the other hand, this may be my perfect excuse to fit a new set of vintage sounding alnicos... John, i think if nothing else, this is a truly interesting case for diagnostic development. judging by the symptoms (BTW you're a great patient to supply all those details) it sounds like there is a break in the coil winding, but not right at the end. (probably badly kinked during the winding process and barely hanging on by a thread. not sure why it finally failed completely.) the overlap of the windings of the coil is whats providing some capacitance. running this and a normal coil in series, i would expect that the load on them would be moderately high resistance ~250k so although being a bit light on bass, it should sound kinda like a normal series pair. but when you put them parallel, the good pickup loads the bad one strongly (5~10k dc resistance, impedance somewhat higher than that). so most of the bad coil's signal is dropped across the capacitance. that's my THEORY anyway. no doubt the covers should come off the pups. maybe it is wax potted. a bit of gentle heat might help persuade her out of that dress. (let's hope it's not one of those epoxy chastity belt deals.) start looking for that vintage set, 'cause unless you plan on using a partial winding, or are going to try to rewind it yourself (good excuse to buy a winder?), you will probably need to replace at least this one. but an autopsy is definitely in order. unk
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Post by JohnH on Dec 13, 2005 14:34:16 GMT -5
Unk - thanks, and that is exactly right. I did eventually get into it, with a few squirts of WD40, and unwrapped the coil. That coil wire is SOOO fine - smaller than a hair. The connections to the coil were OK, and I checked that by scraping the enamel off a section of wire 1/4" from where the external wires were joined, to prove a connection using a multimeter. Still no overall connection end to end, so the break must be deep. I peeled off a few more turns, but it looked like I was heading for a tangled mess.
New GFS vintage alnicos are on their way....
John
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