Diagnosis of Electrical Issue in Recording Electric Guitar

Aiwin

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Nov 29, 2011
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I've concluded that my electric Ibanez RX 160 has an electrical problem. I would like to know if you all agree with this, or if you have suggestions for tests I haven't tried.

The problem: when I run the guitar directly into my Presonus Firebox there is a persistent, loud hissing and crackling regardless of whether I'm playing or not, and regardless of the positions of the pickup switch, volume or tone knobs, all of which have been cleaned with contact cleaner recently, more than once.

This could be a problem with my PC or my Firebox, so here are the tests I've tried:

- playing any one of several other electric and electric/acoustic guitars, run directly through either Firebox inputs (I've tried both), results in no hissing or crackling.
- recording with a condenser mic through either Firebox input results in no hissing or crackling
- playing the Ibanez through a regular guitar amp results in no hissing or crackling
- playing the Ibanez through my Line 6 Pod, with the signal routed from my pod into the Firebox, results in no hissing or crackling!

I've used the same cords for these tests. My best guess as to why the last option (routing through Pod to Firebox) results in no excess noise is that the Pod is somehow cleaning the signal up before it gets to my Firebox. This guess supposes that the Firebox is somehow "more sensitive" than the guitar amp or the Pod are - if that guess is true, then it makes sense to me.

Does anyone see a problem with my thinking, here? Is there a more definitive test I can do? I've looked at the pickup and at the electronics through the back of the body, and I don't find any loose wires or broken solder, though a good deal of the wiring in back is exposed, which is the only possible source I can think of for the hissing/crackling. I'm clearly no electrician but I think the wires in the back should be fully sheathed, more or less.
 

everlost

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sounds like you might have a ground loop. but i cannot think of why only one instument would give you trouble, unless the instrument is at fault.

the exposed wireing may very well be part of your trouble. however, you should have one wire (it could be bare anyway) that connects each pickup, switch, nobe, and plug to the bridge.

edit: i found a schematic on the ibanez site that says i am wrong. depending on your pickup configuration, you could have more or less wires grounded.
 

Aiwin

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I really appreciate the thoughtful replies.

I've taken a photo that might help. Hopefully this shows correctly. If I knew anything about electronics (I'm a beginner!), I feel like the exposed wire here would lead me to an immediate conclusion that this is obviously the source of the problem.

I've looked at the wiring diagam and while I don't understand it fully, it looks like the open wiring that extends from the green sheath (see image) might connect to one pickup, or muliple pickups. This wiring looks like it could easily be the culprit. What do you all think?

 

everlost

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From what I can see, the bare wire is the ground. Each pick up would have the same kind of cable.

Assuming that is your lower pickup, all the bare wires should be soldered together in the volume control. plus a few more. The yellow wire, the one that looks like it has a fabric insulation, looks out of place. A repair, or mod? It's not the kind of wire I would expect in guitar wireing. Or any place other than your homes walls.

Each wire should go somewhere, no free ends.
 

Aiwin

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That's a good point - I don't see a yellow wire anyplace on the wiring diagram, now that I think of it. I'm not the original owner so this could have been eithr a repair or a custom modification, but I wouldn't know. Thanks for pointing this out. If the yellow wire is the culprit then I think I might just leave this alone... it plays fine through regular amps, and I have better electric guitars to use for recording purposes anyway.

I just wanted to get to the bottom of the problem and, ultimately, reassure myself that the noise wasn't resulting from a problem with my recording equipment, which doesn't seem to be the case at all. Gladly!
 

everlost

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That guitar defiantly was modified, your selector switch is missing a wire, and one pickup looks reversed, and another might have been replaced, guessing by wire colors. Another thing to consider is the condition of the filtering capacitors. But you will need a cap checker, or a DMM with a farad setting to learn anything.

Never thought I would be troubleshooting a guitar on a computer forum...
 
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