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| potentiameter snafu http://w-ww.luthiersforum.com/forum/viewtopic.php?f=10123&t=35121 |
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| Author: | Starn [ Thu Jan 26, 2012 8:31 am ] |
| Post subject: | potentiameter snafu |
Greetings from Brazil, I am newbe to this forum. I am from USA but married a Brazilan and moved here 22 years ago. I been working on all kinds of stringed instruments since I was old enough to build cigar box guitar (1964) . I cut my teeth in 84 when I bought out a burnt down music store and spent two years restoring all the booty. I have built or repaired a couple of hundred axes since then and am working full time as luthier here at home. I recently refinished and customized a Jem clone with HSH pickups and 5way switch...pickups are used from USA but work fine(Ebay deal) and switch is new as well as jack...the problem is this...I can´t get the volume pot to work till its up to like 7 !!! I have tried 6 different pots 500k a/b and 250k a/b and nothing solves this problem?? I hook up the switch directly to jack and great volume from all pickups out of amp...I must have checked all solders and grounds a dozen times....I have called all my local luthier friends ( I taught them English) and they say bring the guitar to them to look at it....I been fixing guitars when they were in diapers so that is last resort. Any pro-luthiers ever have this kind of problem? Only thing I suspect is pickups since they are used...but they work and impedence values within limits and no noise....I am stumped but gotta figure this out...anybody have any ideas..passive pickups with gotoh pots should work live a breeze...Murphy must be playing tricks on me. thanks for any help . I talked to my electronics Gur and he told me that the vlores for the bigger pots and mini pots are now inverted by the factories. Big A is now mini B, big B is now mini A....not that it makes any diff in my case...he gave me some ideas to trouble shoot the circuit and I will also measure the pickup magnets (guass) to see if that could be prlb...doubt they cold loose that much magnatism!! but with Murphy anything could happen.ciao,Dennis |
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| Author: | VirgilGuitar [ Thu Jan 26, 2012 9:54 am ] |
| Post subject: | Re: potentiameter snafu |
Sounds like you are using active pickups and are placing them in a passive environment. |
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| Author: | MikeH [ Thu Jan 26, 2012 2:02 pm ] |
| Post subject: | Re: potentiameter snafu |
Do you know what brand/model the pickups are? And is the issue present on all pickups? Sounds to me like a wrong taper pot. At least that is one possibility. Could also just be bum pots. Were all of the pots you tried from the same batch? I've had similar problems with amp builds, and it was generally due to a bad spot on the pot. Although from 7 to 0 would be quite a bad spot... |
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| Author: | theguitarwhisperer [ Thu Jan 26, 2012 8:19 pm ] |
| Post subject: | Re: potentiameter snafu |
Is the problem low output, or is the output strong once it's there? If the output is good, then +1 that the problem is most likely the taper of the pots. They should be specified as audio taper. |
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| Author: | Starn [ Fri Jan 27, 2012 11:19 am ] |
| Post subject: | Re: potentiameter snafu |
thaks to all for the great feedback. Three different sets of pots, first set mini pots Chinese cheapos..tested and works, second set large chinese cheapos..tested and works, third set Gotoh Jap one large and one mini..tested and works.. I don´t know if the pickups are for active or passive since just bought them cheap off Ebay...but I had built a guitar with active pickups running passive and I didn´t have any problems with volume...just not much punch due to low impedice of something around 4 for humbuckers.... how to tell if pickups are passive or active is good question since they don´t have any marking or fab sticker.....how does one tell?? any kind of test I can do... I will try another pickup that I know is passive and then changed them all if needs be...but there goes my profits out the shop....everything here cost 3X the price because of high import taxes and regular taxes...people in USA don´t understand how it is to be taxed to the max...wait for the elections !!!! |
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| Author: | theguitarwhisperer [ Fri Jan 27, 2012 5:34 pm ] |
| Post subject: | Re: potentiameter snafu |
The best way to tell whether they are active or passive is by the brand name and model. Active pickups will have some kind of power supply lead. Some guitars have active EQ paired with passive pickups. In that case the pickups will not have a battery lead but the potentiometers will. |
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| Author: | MikeH [ Mon Jan 30, 2012 12:18 pm ] |
| Post subject: | Re: potentiameter snafu |
Starn wrote: I hook up the switch directly to jack and great volume from all pickups out of amp... If this is the case then I think your pickup selection is fine. In my experience, active pickups will generally not work, or sound really, really awful without a power supply. I would say the issue lies in you pot selection, either taper or value, or in your wiring/grounding scheme. Eliminate variables: You said it works fine when wired directly to the jack. Then try adding just one volume control, then another, then tone, etc. The culprit will emerge. I've had to figure out what value pot to use before without any information to tell me what it should be. I usually start with a 1M pot and solder resistors is parallel until I find the value that has the approptiate range. Then I consider what the taper should be. Then I buy the correct pot. |
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| Author: | theguitarwhisperer [ Tue Jan 31, 2012 6:16 pm ] |
| Post subject: | Re: potentiameter snafu |
If they are passive humbuckers, 500K audio taper is the industry standard for most guitars, including high end instruments. If you get a good quality audio taper potentiometer, like CTS, then you should be fine. I should add that if you are a lefty, you need reverse audio taper and wire them the opposite of most standard wiring diagrams. |
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| Author: | Starn [ Tue Feb 07, 2012 6:47 pm ] |
| Post subject: | Re: potentiameter snafu |
Thanks you all for the great feedback/input. I finally went to a freindly luthier who has been active the last 20 years working with repairs (300 per month) and he saw the problem in two minutes!! I painted the area for the jack with conductive shielding paint and the positive to the output jack was shorting on the paint....I over did the shielding and underdid the isolation on the jack. I sanded out the paint and isolated the connections on another output jack that wouldn´t touch the body...gee, did I feel dumb...do I feel dumb, old age must be getting to me...so if anybody has this kind of problem with pots and pickups then I hope my errors will show some light to otheres...one for the books on how to make problems which seem unsolvable when not seen in correct perspective. thanks to all.ciao |
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| Author: | RogerC108 [ Wed Feb 08, 2012 8:51 am ] |
| Post subject: | Re: potentiameter snafu |
Good to hear that you got things sorted out. That's not something I would've ever thought of, so thanks for sharing this with us. |
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| Author: | Chameleon [ Wed Feb 08, 2012 11:32 am ] |
| Post subject: | Re: potentiameter snafu |
I've had that one before. You should feel empowered now. I always feel like a stronger man once I find out how to fix a problem like this. You now have one more trick under your belt. |
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