camiam
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Post by camiam on Sept 2, 2006 19:23:36 GMT -5
Hi everyone. I'm new to the boards, but have been lurking for a bit. I recently attempted to perform QTB on a '98 MIJ squier. After using aluminum foil to shield the guard and cavity, and following the directions on re-wiring (using a 1uf, 250V cap to isolate strings, all radioshack had), the guitar hum is unchanged, and identical to my brother's stock MIM Strat. There is no change in hum when i touch any metal anywhere on the guitar, with the exception of the metal 5-way switch. The hum changes in volume depending on the position and angle of my guitar with respect to the amplifier. I don't know what's the deal, but I am loath to disassemble the guitar yet again without a really good idea of what's going on. The guitar had almost identical wiring to the picture here, with one difference, which is here, I left the wires like this b/c there was no mention of changing them, and all pickups and tone controls work as-is. Is this the cause of my noise? I would be much appreciative of any advice.
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Post by sumgai on Sept 2, 2006 22:00:13 GMT -5
cammy, Hi, and to the boards! Well, OK, welcome to finally coming out of the closet! Your 1mfd, 250volt jobbie.... did that happen to be an electrolytic, by any chance? Such things don't work very well in this application, sorry to say. And 1mfd is overkill, whereas 0.2, 0.22, or 0.33 mfd can all be found, and will work just fine. The real "killer" here is the voltage rating. The 400 volts specified in the article is due to many tube amplifiers using much more than 250 volts. Your unit would fail under severe conditions, and may not provide adequate protection. Otherwise, suspect one or more bad solder joints. Start with the joint at the spring claw, even if you didn't mess with it at all. Sometimes things go bump in the night, doncha know! HTH sumgai
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camiam
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Post by camiam on Sept 2, 2006 22:40:02 GMT -5
Nope, it's a metal-film capacitor. I admit to being ignorant to the meaning of different voltages, but I play with solid state stuff anyway (alliteration is awesome!).
I did, infact, resolder the grounding wire, but it's not to the claw screw, it's to the large metal plate the claw screws pull on, should I solder directly to the screw? And, is there anyway to systematically diagnose which solder joint would be poorly done short of opening 'er up and examining every one?
I hesitate at taking the scratchgaurd off again because it's only an 8-holer and one of the screw holes has already stripped-refilled-and stripped again.
Thanks for the help!
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Post by sumgai on Sept 2, 2006 23:23:08 GMT -5
cammy, Well, scratch that idea. The wire should never go to a screw in the first place, it belongs on the claw. Imagine trying to turn the screw to adjust the spring tension, and the ground wire gets wrapped around it about 20 times. Nope. Visual inspection is the name of the game here. If you've soldered more than, say, a hundred joints, then you probably know what to look for in a bad joint. If not, just ask. The only thing I'd say is a system is to start at one end, move towards the other end joint by joint, and don't skip around. If you have to branch off, do that, then come right back to where you "forked", and follow the next/other/remaining branch. That's easy to fix. Grab some Elmer's Wood Glue, or Elmer's Carpenter's Glue, and a toothpick. Dab some glue down the hole, insert the toothpick, and break it off! Keep inserting sections of the toothpick until the hole is full. Give it overnight to dry out, then re-open the hole with a small drill bit, to act as a pilot hole for the screw. Good as new! Da nada! ;D sumgai
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Post by sumgai on Sept 2, 2006 23:27:14 GMT -5
cammy, Just realized, I haven't answered your final question..... Nope. The two wires you indicated are reversible, no problem. Meaning, the original drawing was done for clarity (fewer crossed wires), but your version is just as good, and you left it alone for all the right reasons. HTH sumgai
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camiam
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Post by camiam on Sept 3, 2006 19:57:39 GMT -5
Alright, I've re-soldered the grounding wire, and am now rechecking all of the soldered connections. Am I correct in stating:
Good joint:
*Shiny finish
*Well spread solder
*Doesn't crack when wiggled slightly
Bad Joint:
*Dull grey finish, possibly with specks in it
*Solder may be "balled" or "bunched" up
*Gross nasty rosin everywhere
*Possibility of cracking when wiggled slightly
Which brings me to another question, what's better for desoldering inside a guitar, a desoldering pump or braid? I have a length of braid now, but sometimes I wonder if a pump would be easier?
Another question that I think may be important is: Why does the hum get louder when I touch the switch, but not any other metal on the outside? Is this indicative of a short? If so, how should I fix it, the aluminum foil I used is already glued onto the pick-guard pretty snugly.
Thank you so much for all of your help! ;D
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Post by sumgai on Sept 3, 2006 20:51:14 GMT -5
cam, Your analysis of good and bad solder joints is right on! Go to the head of the class. That really is a personal preference, but I've used both for so long that if someone took one of them away from my bench, and said I couldn't ever have it again, I'd be just as happy with the remaining item. For me, they both work well. Some things to think about. A pump can be jerky, whereas a braid is steady. OTOH, a braid can be oversized for the workarea. I've seen it transfer heat to a nearby joint, then leave behind a "solder bridge". I've seen that done time and again, in small work. (Back when I had visual acuity that a fellow could be proud of! Both have their uses. But FWIW, the pro's use a vacuum-equipped soldering station, where the action is right at the tip of the iron, and is on at all times - no sudden jerk, and no throwing out used wick afterwards. Very indicative of the switch's body being shorted to the output signal. I'd hazard a guess that the output wire is bare in one spot, and that spot is touching the switch body. Either that, or you have the mother of all solder bridges in there somewhere! If the switch is directly contacting the aluminum foil, then that foil is also at "hot", and not at ground. Perhaps it is what's actually touching the bare wire somewhere. But know this, the foil is not at ground potential (if the switch is actually touching it). That means that your shielding job is not up to snuff. I'd recommend that you take it back apart, and use an ohmmeter to check things out. What you should be getting, and what you're actually getting, are two entirely different things. And that ain't good, IMO. HTH sumgai
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camiam
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Post by camiam on Sept 3, 2006 23:12:37 GMT -5
I apologize for all the questions , but I want to make sure I'm doing this correctly. Alright. This makes sense, but how would I tell what's happening and then fix it? Not up to snuff period? Or only if the switch touches it does the shielding fail? I've got one of these ohm-a-thingies, I think. What am I supposed to be looking for? I'm sorry for all the questions, I feel so dumb . I just don't want to go through all this time and effort re-wiring this beast and have the same amount of hum as if I didn't do anything. And I've isolated it to the guitar. Tested with 3 different cables, 5 different house outlets, and 2 different houses. On the bright side, I've managed to greatly improve my soldering, and I've only burnt myself once! ;D ;D
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Post by sumgai on Sept 4, 2006 3:15:29 GMT -5
cammy, Any solder job you can walk away from with all your fingers still attached is a good solder job! ;D Not from the outside, I can promise you that. Visual inspection is the first thing, once the guitar is laying open on the operating table. You'll also need your ohmmeter to take readings that can be more definitive. Not period. If the shielding is touching your switch, and you don't get any reduction in hum, then the shielding is not connected to ground. And that was the whole purpose of shielding the first place, wasn't it? But the bright spot in the dark scenario may be that the switch is not touching anything at all (which is a minor no-no, not a major screw-up. Since we're not trying to get an exact measurement on a coil, nor on a control (pot), the answer is simple...... a reading of zero or nearly zero means that you have a connection between the two points where your test leads are touching the circuit. If your meter says "OL", it means that you have an open circuit - no continuity. In this case, put one of the test leads on the switch body, and the other on the shielding. You'd like to see zero ohms, but a few ohms is OK, too. If it's higher than say, 25 or 30 ohms, it'll likely be on the order of greater than 1 meg, and very like it will read "OL". That's a bad thing, and you need to correct it. Since you say that touching every other metal part does reduce the hum, you needn't make any tests anywhere else. HTH! sumgai
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camiam
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Post by camiam on Sept 4, 2006 16:47:43 GMT -5
In this case, put one of the test leads on the switch body, and the other on the shielding. You'd like to see zero ohms, but a few ohms is OK, too. If it's higher than say, 25 or 30 ohms, it'll likely be on the order of greater than 1 meg, and very like it will read "OL". That's a bad thing, and you need to correct it. Okay, one lead on body, one lead on pickguard shielding (or anywhere on the guitar, for that matter). Reading: Infinite Ohms. So it's bad. This means the switch is not grounded, I presume. How does one fix this? The output wire (wire to output jack, correct?) doesn't come anywhere near the switch I checked every other joint with the ohmmeter, and they were all good. Am I to assume I'm supposed to get an infinite reading across the capacitor? Touching any other metal has no discernable impact on hum. One more observation: If I point the pickguard straight up toward the flourescent lights, the hum sounds like I didn't do anything. If I point the guard straight at the amp (perpendicular to lights) The hum drops by quite a bit, but still far from "very quiet" of even cheap humbuckers.
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Post by ccoleman on Sept 4, 2006 18:12:45 GMT -5
I would try touching a normal insulated wire (stripped ends) from the metal of the switch casing, to the star ground point, and see if the hum goes away.
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camiam
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Post by camiam on Sept 4, 2006 21:36:40 GMT -5
Just tested out your idea ccoleman. The only problem is my switch has a plastic housing. But when the wire is ran from the switch body itself (the part you put the little plastic knobby on) to the star ground, the buzz from the switch does vanish.
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Post by ccoleman on Sept 5, 2006 11:37:04 GMT -5
ok so at this point I would try making that wiring (switch housing to star ground) permanent enough so that you can try to play some notes, switch pickup positions, and see if your guitar works like it should. and if yes, solder that ground wire permanently in place (if there is nowhere on the switch body to do so, get one of those rings that contact onto the metal of the threaded switch shaft, install that on the switch and solder onto that), and you are done. Congrats !
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