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Where to look for a problem with new wiring producing no sound

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  • RobRed
    replied
    Thanks, Terry. I will apply your recommendation when I get to that point. I don't think putting pictures up will help. The schematics are straightforward and certainly not part of the problem, and the wiring is tight enough that it would be really hard to tell looking at the photos I took what's what or to hope to find a problem from looking at the photos. Thanks, again. Rob

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  • RobRed
    replied
    Thanks, Mick. That is the basis of the whole problem, as I have outlined it in my detailed response to Dave H. I can't test anything on this other than the pups, the bridge block, and the output jack, unless I disassemble the guitar, and that was the basis for my putting the question up. Basically, I couldn't figure out how to assess the problem and reassemble the guitar without potentially recreating the damage and having to go through the whole thing all over again, and I just didn't want to go through that. I have decided, since this is a nothing special knock-off guitar, to open the wiring cavity right through to the back of the instrument and enlarge it. Then there will be less likelihood of damage on reassembling it once I've corrected the wiring, and if there is a problem, I may be able to deal with it without taking the guitar apart yet again, just by working through the open back of the cavity. Thanks for your suggestion. I will apply that when I do disassemble the guitar and try to figure out what went wrong. Rob

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  • RobRed
    replied
    Originally posted by Dave H View Post
    I'd try a few simple measurements before cutting a hole in the back.
    You can also do simple measurements to check the control plate wiring before final assembly.

    Do you have a digital multimeter? A cheap one will be good enough.
    Connect a cord to the guitar and check for continuity (< 1 ohm) between the sleeve of the jack and the guitar's bridge and control plate. Then connect the meter between the jack tip and sleeve, turn the vol pot fully CW and measure the resistance in each position of the PU switch. For a stock Tele it should measure something like 6k in the bridge and neck positions and 3k in the middle position (I'm not sure what your fourth position does). Now turn the vol to zero and it should measure low resistance (< a few ohms) for all PU selections.
    I thank all who have responded but am responding to you because you didn't like my idea of cutting into the back of the guitar. I'll put it this way. I am very confident of my soldering and followed the schematic flawlessly. I have done ridiculously more complex projects than this and had no problem whatsoever, and I checked everything carefully before I put this guitar together. The main problem as I assembled it was that it required a somewhat uncomfortable push to make the wiring fit in the existing cavity, and I must wonder if, with the four-way switch that came with the wiring kit I got, it is just a bit too large to fit in the existing cavity with the wiring, and pushing it into place either pulled a connection loose or resulted in a ground to the conductive paint I coated the cavity with at a point in the wiring where a ground connection is, let's say, inconvenient.

    This is not a collectible instrument that I will be diminishing the value of by cutting into it. It is a knock-off hollow-bodied Tele by a brand that turned out to be much junkier than the reviews suggested (which is exactly why I rewired the thing in the first place). It will be a bit of a nuisance to do the work, but I am a woodworker, and I have done similar work on guitars before. One of my complex projects was to take an Ibanez solid-body that I found cheap at a flea market, put some much better pickups on it, insulate the cavities, and rewire it to have four pots and 6 mini switches. The fourth pot is a tone control I built that uses a rotary selector switch to choose among 6 capacitors. It's huge. The mini switches allow me to select among the two single coils in neck and mid positions and either pole of the bridge humbucker and then have them running in parallel or series and in and out of phase. You have to know I was compelled to enlarge the wiring cavity dramatically to fit all that stuff in there, but it worked fine. I got a sheet of cover plate material and made plates for front and back that look like they could have been original to the instrument. And again, as complicated as that project was, it works fine. I am very careful with electronic work.

    I have a good quality multi-meter by Fluke, but the problem is, I already know without question that something is not right, and the only way I can really determine what it is is to disassemble the instrument. That is not a small or insignificant trick. It means removing a perfectly good, brand new set of strings that will not go back on this guitar and may be wasted (with the bend in the end of the strings from having been wound on the tuners, they get caught up on the back of the pick guard coming through the instrument and will not push through). It means the nuisance of disconnecting the neck pup from the pick guard. Neither of those is a life altering event, but the potential of having to do them repeatedly turns me off.
    Then I could determine what got fouled up when I forced the electronics into the tiny, narrow cavity, and fix whatever it is, and just mess it up again and potentially go through the whole thing repeatedly, by having something fouled up when I again try to make things fit where they really don't quite fit.

    If I open up the cavity from the back, it will offer two major benefits that will put this to rest. First, it will make it so things fit better and I don't have to worry about damaging the wiring or creating a short by trying to make it fit together. It will be deeper, so the switch should not come close to reaching the back of the cavity, and I can make it wider, too, to leave more room for the wires. Second, if in spite of that I put it together and still have a problem, I'll be able to do exhaustive analysis and find and potentially repair the problem without taking the instrument apart yet again. It is a junk guitar that I hope to make work better than it was designed to work, and it won't bother me at all to have access to the electronics through the back of the instrument, even though it was not an intended part of the design. It's not the dire error I would make if I cut open the back of a true Tele.

    Thanks, again. Rob

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  • big_teee
    replied
    Like Dave H said.
    I start with a guitar cord plugged into jack and start checking ohms continuity from the jack to pots and switch, with a multimeter.
    Like said, some pictures will help on advice on how to proceed.
    GL,
    T

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  • Dave H
    replied
    I'd try a few simple measurements before cutting a hole in the back.
    You can also do simple measurements to check the control plate wiring before final assembly.

    Do you have a digital multimeter? A cheap one will be good enough.
    Connect a cord to the guitar and check for continuity (< 1 ohm) between the sleeve of the jack and the guitar's bridge and control plate. Then connect the meter between the jack tip and sleeve, turn the vol pot fully CW and measure the resistance in each position of the PU switch. For a stock Tele it should measure something like 6k in the bridge and neck positions and 3k in the middle position (I'm not sure what your fourth position does). Now turn the vol to zero and it should measure low resistance (< a few ohms) for all PU selections.

    Leave a comment:


  • Mick Bailey
    replied
    There's an old technique called the 'disruption test'. Basically. plug the guitar in and use an uninsulated metal probe to check through the main connection points in your guitar. Begin with the hot terminal of the output socket. Loud buzz? move to where that connects. Then back from there through pots and switches. Turn your pots right up. Everywhere you would expect to get a signal, you should hear a buzz through your amp when you touch that point.

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  • RobRed
    replied
    Originally posted by eschertron View Post
    "no sound" can result from a simple wiring mistake at any number of points in the wiring harness. With all the wiring new, then all the wiring becomes suspect. A lot of ground to cover.
    If you can, post pictures that show the entire cavity, and annotate which wires/colors go to which pickups. Four-way switch? Please post what it's supposed to do and how it is supposed to wired up. Maybe help can come that way.

    If there is a ground connection missing, that could kill the sound. But again, lots of choices. If the grounds are not optimal (but present), you'll get a little extra noise in your signal.

    Just thinking out loud. No sound? No crackling when the pots are turned? No hiss, no hum? Start with the jack wiring.
    Thanks for your prompt reply. Boy, did this get me thinking about a lot of stuff. It is really too much for me to include in detail in this context, so I will try to keep somewhat brief and focused.

    I will follow your last recommendation, to start with the output jack. In fact, just before I went to bed last night, I looked that topic up online and came to find that one of the resources I had used mislabeled which terminal was which, so I went to bed hoping all I would have to do is pull out the outlet and switch the wires. Unfortunately, I found another discussion this morning that said, if the lead and ground are switched on the output, you should still get sound, but it will just be muddy, noisy, and ugly. For now, I am going to hope that individual was mistaken, because to have to sort this out otherwise will represent a huge inconvenient mess.

    Part of the problem is that all the wiring is done on the back of the pick guard. There is a cavity for the wiring to fit into, but you can't view it in the cavity. It's just a narrow hole in the front of the body of the guitar for the wiring to fit into. If switching lead and ground on the jack doesn't fix the problem, it will be a mess. I will have to remove the strings and then remove the neck pup from the pick guard, before I can flip it over to assess the problem. Then to test whatever I think might have fixed it, I will have to remount the pickup, then the pick guard, and finally the strings. That is absurd. In fact, if it is not the jack, I can only wonder if damage was done to my correctly done wiring by having to jam it down into the narrow cavity sight unseen. In the end, I've come to the conclusion, that if rewiring the jack doesn't fix the problem, I am going to open the body up from the back to enlarge the wiring cavity and allow testing and examination of the contents without having to take the guitar apart like that. It will be a job, but it will be far less of a nuisance than trying to figure it out as it is. I would then just have to enlarge the cavity, open it up to the back of the guitar, paint the newly exposed surfaces with electrical paint, and create a cover plate for the new opening in the back of the instrument. That would allow me to test my work until it was functional in a sane manner.

    Thanks, again. Rob

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  • eschertron
    replied
    "no sound" can result from a simple wiring mistake at any number of points in the wiring harness. With all the wiring new, then all the wiring becomes suspect. A lot of ground to cover.
    If you can, post pictures that show the entire cavity, and annotate which wires/colors go to which pickups. Four-way switch? Please post what it's supposed to do and how it is supposed to wired up. Maybe help can come that way.

    If there is a ground connection missing, that could kill the sound. But again, lots of choices. If the grounds are not optimal (but present), you'll get a little extra noise in your signal.

    Just thinking out loud. No sound? No crackling when the pots are turned? No hiss, no hum? Start with the jack wiring.

    Leave a comment:


  • Where to look for a problem with new wiring producing no sound

    Hello:

    I just rewired a knock-off hollow-body Tele. It had gotten wonderful reviews online, but when I got it home, it was just terrible. I have to wonder whether the manufacturer and family and friends were responsible for the wonderful reviews. I plugged it in and got the worst hum I've ever heard from a guitar in my life. The fret ends were so sharp, I could have cut the skin of my left hand playing the thing. I could not produce any musical sound worth listening to on it.

    My response was to decide to rewire it and upgrade it. I got new pickups. I got a wiring kit with a four-way switch. I got heavy brass bridge saddles. I got tools to dress the frets, which were just awful. Anyway, I am confident of my soldering technique, followed the schematic carefully, cautiously checked all connections by gently tugging on them, and all appeared fine, but when I got it all put together and plugged it in, there was no sound through any of the 4 pickup selectors.

    The instructions said that if neither a metal control plate or some kind of shielding plate was being used, the tone pot needed to be grounded to the volume pot. With the horrendous hum when the guitar was new, I painted all of the cavities with conducting paint and used the plastic finger guard, to which the neck pickup is mounted, with a foil shield pasted on the underside, in direct contact with a considerable area of the conducting paint. I was unsure, even though I thought it likely, whether this was what they meant by a shielding plate, so I did ground the tone pot to the volume pot. Is there potential that that is why I am getting no sound, or is that just a redundancy that shouldn't cause an adverse effect? I think I have a half a memory that too many ground connections can cause trouble, and that would certainly be an easy thing to fix if it is the likely cause. If that does not seem a likely explanation, though, how on earth do I sort this out, when everything looked just as it was supposed to be?

    Rob
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