I have problem with my Ibanez S450 (hsh, 5way switch) picking noise. I've decided to try to fight it, but I'm not sure if rewiring can really help; electronics seems to be rather well shielded (electronics and pickup chambers covered with conductive paint, chamber's cover with aluminium screen, all wires shielded). The only improvement I can think of, is to separate signal/screen grounds and reroute wires to utlize actual star grounding (at the moment there is main ground point on the volume knob, but some signal wires are grounded somewhere else).
Back to my point - what do I miss after reading articles/browsing forum - is a simple test that would tell if rewiring can actually improve anything. I've came to an idea just to solder one of pickups directly to the input jack and provide ground for all the screens - this sould actually eliminate all the possible ground loops within signal path and isolate problem to pickup itself; if it hums as before - rewiring probably wont help.
As for "my" hum - it seems to be 50Hz/100Hz, its level follows volume knob setting, also it reacts to tone control just as a pickup signal. With single coil is most visible, a bit less with humbuckers, h+s and s+h configs seem to be most quiet...
Your test scenario is the proper way to find out quickly if a full re-wiring job will help, or not. One pickup, no controls, one jack - what could be more simple than that? Your assumption is correct - if there's still hum, then it's not the wiring that's the problem, it's the pickup itself (or all the pickups, themselves).
The fact that you get less noise with certain combinations only means that they're combined together (by the switch) in the proper way - they (at least one of 'em, or possibly all three of 'em) could still be bad in the sense of not rejecting outside interference. Can you take a photo of the guitar's innards, and post it for us, please?
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Can you take a photo of the guitar's innards, and post it for us, please?
I'll do it, but first I have to borrow better camera . I have to repeat my yesterday's test, as it seems I've wired only half of my humbucker.
I've prepared wiring diagram, there is no official one available anywhere.
It seems HB's have earth at the screen, white is midpoint and red is hot. Could anyone confirm this is common HB wiring?
Ah - grounds on the diagram do not exactly match my setup (actually pickups are grounded at the 5way switch, etc) - but still there seems to be no obvoius ground loop (but additional weak ground provided by conductive paint).
As for noise - it's level is can be altered by changing orientation of guitar in the space - but I'm not sure if this actually tells anything about the problem.
I'm wondering what should be the level of noise in well shielded guitar with good hb pickups? Any simple way to measure it? (I'm still looking for oscilloscope...).
I've made some experiments, but I didn't get any wiser than before. So far it seems to me, that both humbuckers do not cancel out noise as much as I'd like them to do, or hum that gets into the signal is induced somewhere else.
I'm wondering, how could I measure if hum level at the pickup output is within reasonable range. Actually - not even really sure what value is used to measure "humbucking" abilities of pickup. Probably - noise level related to output level (single sustaining string? peak at the attack? "typical" non-humbucking pickup), or maybe just the level of noise induced by well known source?
I've tried to use (crappy) soundcard, to find out whats going on, but even with it's input shorted it gives strong hum on the low end by itself - so only visible effect of increasing volume on the guitar (what "enables" hum) is rising left part of spectrum a bit (with no obvious peak appearing). Doesn't seem to be usable as measurement tool... I thought I'll build opamp based buffer with known gain - then it would be easier to measure anything.
As for guitar shielding - wiring one of humbuckers directly to output jack didn't change anything - so it seems wiring is not the problem.
Below there are some (unfortunately lo-fi...) photos of guitar wiring.
Do you have any information on the two lever switches that you are showing?
That is single switch - OTAX VLX91, used in most Ibanez guitars - 4 sections, 5 positions. On the wiring diagram drawn as two halves (view on the front and the back of switch). Lever additionally drawn by hand, is set to the bridge position, and small dotted lines show how connections are set up then (common pins are at the lower side of switch, the actuator for each section shorts common one with corresponding pin above).
I own basically the same guitar. Mine is a 470S model, but looks to have the same pickups and wiring as yours. I would describe mine as being pretty quiet, certainly quieter than my "Strat" (which is awaiting a shielding job), or either of my Tele-types.
I don't know of any testing of hum that you could use, except by comparison to other guitars plugged into the same amp in the same room. But before you tear the guitar apart, you may want to do some comparison testing, particularly if you have or can borrow a single-coil equipped guitar for that purpose.
Anyway, FWIW, my Ibanez, while not "silent" in the SC position(s), doesn't present a noise problem in comparison to my other guitars, it's one of the quietest that I have. My suspicion in your case would focus first on the environment, electrically speaking, where you play, based on your statement that the noise varies as you move around.
And, as always, a quality guitar cord is a good starting point.