Author Topic: Multimeter shows pots resistance instead of pickup resistance when conn to jack  (Read 618 times)

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Offline Rango

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Hi guys. So i rewired my guitar for 50s wiring and i connected guitar cable to output jack and measured it with multi-meter to see if pickups are working.

The multimeter is showing pots resistance of 500k at volume of 10 but it should show pickup resistance instead. When i switch to neck and then bridge pickup it always tops out at 500k which tells me it's measuring pots resistance. When i roll volume pots the resistance is obviously changing but the resistance is between 50 -500k omhs and pickups are 8.14k omhs and 14.40k omhs.

I have measured the pickups resistance before installation and they were working at 8.14k ohm neck and 14.4k ohm bridge so i know they were working before install so i know they're working.

Did i ground pickups somehow or what have i connected wrong that it's not measuring pickups resistance when playing with pots volume?

I don't have an amp yet so i can't connect to it and test it but multi-meter, the tool of troubleshooting is showing pots value instead of pickups value when connected to output jack so I'm assuming something is not right here?

What did i do wrong in electronic wiring? Any help in troubleshooting this would be greatly appreciated.

Ref: https://www.seymourduncan.com/blog/tips-and-tricks/lespaulwiring
« Last Edit: October 22, 2019, 02:14:45 am by Rango »
 

Offline bob91343

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I can't see enough detail to help.  But check that the grounds are connected properly.  If the pickup is connected to the pot and the pot rotated, the ohmmeter should see the resistance change.

Otherwise you have a miswiring error.
 

Offline floobydust

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I think the pickups are not wired right - each one (bridge, neck) has two wires? (red,white) and you soldered them to the same spot? One should go to ground i.e. white, and the red goes to the pot's wiper.

I would find 14AWG house wiring as too thick for a ground buss wire, it just needs so much heat to solder without cooking the pots. You can attach other grounds soldered to the wire between the pots, it's less heat.
Best not to have a loop or circle in the pots' grounding wire, try a letter "C" instead.
 

Offline Cubdriver

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Do your pickups have white and red wires only?  It looks like you have both connected to the lower terminal on each of the volume pots - they're shorted.  One of them needs to go to that lower pot terminal, and the other to the grounded side of the pot.

-Pat
If it jams, force it.  If it breaks, you needed a new one anyway...
 

Offline Cubdriver

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I *think* this is how you have it:




And this is how it SHOULD be wired:




-Pat
If it jams, force it.  If it breaks, you needed a new one anyway...
 

Offline Rango

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Thank you guys. So i fixed the white cable. That cable was coil splitter and suppose to be loose on side tapped off with electrical tape, as i'm not coil splitting. As the green cable in diagram which i don't have. If you guys click on picture it shows bigger, but i think you know that. I can make bigger pictures if needed.

The current state is as follows but i now i'm getting O.L (no connection) so now i think i've probably grounded something. I've also disconnected the last leg of copper ground wire on back of the pots so now is C letter, not lopping hopefully.

I think i'm having an issue with wiring of switch to jack. That's not going well i think and the grounding of the all negatives.

Here is electrical wiring in my guitar (NOT SAME COLOR OF WIRES AS IN DIAGRAM as brand of pickups is different. Oh and i don't have green cable either). It's 4 wires instead of 5. green and white suppose to be not in use anyway so we'll treat green wire like it's not existing in my setup. The goal is to wire as with Thorbak diagram but without green cable. In my case only white wire is handing lose as i have no 5th green wire. That's why i showed here 1st picture of wiring for my pickup but that's modern wiring so not going with that diagram.

white cable = coil tap -- currently soldered off and tapped off with electrical tape loose.
red cable = (+) signal -- soldered to bottom or left volume pot (that's 50s wiring like in thorbak diagram)
black = (- ) ground - soldered to back of volume pot  - this is grounded
Bare/Copper = pickup shield ground -- soldered to back of volume pot - this is grounded

1st picture is MY pickups in the guitar wiring with kwikplug connector which has 4 wires. I just want to show how those pickups are wired with 4 wires instead of 5.
Disregard the caps placement in 1st picture as that's Modern style wiring and i'm going for 50s style wiring shown in 2nd picture. Hope i'm not confusing you guys, if so completely disregard 1st picture. Goal is 2nd diagram wiring.

2nd picture is 50s wiring what i'm trying to achieve but without green wire, as that diagram is 5 wire connector. Again white and green are not used at all so they're just hanging loose.
« Last Edit: October 22, 2019, 07:06:01 am by Rango »
 

Offline alsetalokin4017

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Is that GFS-WIRING.JPG diagram correct? I see the two tone pots grounds and Vol1 ground aren't shown connected to the rest of the system ground so it's hard for me to see how they could be doing anything, unless the pots are mounted on a metal plate with the rest of the controls.

I think you should start over from the beginning.

Let me first see if I understand your pickups. Your pickups are using just the Red and Black wires as the signal and ground, and you are not using the white tap wire at all, right? And you have a bare wire to the pickup shield which will also be grounded. All the pot cases, and the jack ring, will share the common ground.   Is my description correct?

Unfortunately neither diagram shows the 3-way Toggle Switch in a manner that simple country EEs can interpret easily.   ??? 



« Last Edit: October 22, 2019, 02:30:00 pm by alsetalokin4017 »
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Offline Rango

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Is that GFS-WIRING.JPG diagram correct? I see the two tone pots grounds and Vol1 ground aren't shown connected to the rest of the system ground so it's hard for me to see how they could be doing anything, unless the pots are mounted on a metal plate with the rest of the controls.

I think you should start over from the beginning.

Let me first see if I understand your pickups. Your pickups are using just the Red and Black wires as the signal and ground, and you are not using the white tap wire at all, right? And you have a bare wire to the pickup shield which will also be grounded. All the pot cases, and the jack ring, will share the common ground.   Is my description correct?

Unfortunately neither diagram shows the 3-way Toggle Switch in a manner that simple country EEs can interpret easily.   ???

I think what you said is spot on unless i am interpreting something incorrectly.

1st pic: This is how jack should be wired too.  2nd pic: Here is how switch should be wired.

This also is 50s wiring so everything here is correct but disregard that "vol kit" connection. That is not needed there and does not connect.

Also both volume lug grounds are soldered onto back of the pots so each lug is grounded to itself and also that copper wire is also grounding them all to each other. C shaped wire.   

I would say the most accurate 50s wiring diagram is that Thorbak but as you said it's not clearly showing the switch wiring so that 2nd pic below shows how switch is wired to pots. Is that helpful?

Three questions

Can i run ground all the way from switch to ground on jack and do i need another cable then to hit one of the pots as well or it can be just ran to the jack only?

There is also some bare copper wire which is mounted somewhere to the body of the guitar i think, similar how car ground is grounded. Am i suppose also ground this wire. I really don't know where and how this cable is connected if at all to anything. This was installed by guitar maker and i don't know if its actually grounded to body of guitar. What should i do with that wire. Connect or don't?

Can i test this circuit somehow with multi meter, continuity maybe?, and if so which one?




« Last Edit: October 22, 2019, 05:12:13 pm by Rango »
 

Offline alsetalokin4017

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Er.... OK... the second question is the easiest one. This mystery wire that disappears into the body of the guitar goes to the bridge mounting studs and the tailpiece, so that all the exposed metal of the guitar, including the strings, is grounded. This wire will be soldered to the rest of the ground wiring in the pot bay.

The switch diagram doesn't tell us which terminal of the switch is which, and might not correspond to your exact switch.  I've seen many different physical models of 3-way switches and unless you have a picture diagram that shows your exact switch it is going to be hard to figure out from the pictures. Here's a reference just to show how complicated it can get.

https://guitarelectronics.com/guitar-wiring-resources/pickup-switch-terminal-connections/

So once again I recommend starting over from scratch. It might be easiest to assemble the pots, tone caps and switch outside the bay, then stuff them in and connect the pickups and grounds and jack wiring.
The easiest person to fool is yourself. -- Richard Feynman
 

Offline alsetalokin4017

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First question: all the grounds should be connected together, and use the shortest wiring possible for your layout. Two wires come from the jack: one is "positive" and goes to the switch, the other is "ground" or negative and connects to the rest of the ground system.  Technically there are two good methods: "Star" where all grounds come out of a single point, which requires more wire, or "daisy chain" where all grounds are connected in a line, like your "C" for the pot bodies but extended to all the rest of the grounds. Practically, in guitars, you find these  two systems mixed together.

Third question: Do you mean the mystery wire circuit? yes, check for continuity between the free end of the wire and the guitar's bridge mounting studs and tailpiece studs.  Do you mean the rest of the circuit? Also yes but what exactly do you want to check?

« Last Edit: October 22, 2019, 06:29:56 pm by alsetalokin4017 »
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Offline Rango

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Third question: Do you mean the mystery wire circuit? yes, check for continuity between the free end of the wire and the guitar's bridge mounting studs and tailpiece studs.  Do you mean the rest of the circuit? Also yes but what exactly do you want to check?

Thank you. I appreciate your help. Yes the mystery wire. The problem with this wire is it goes inside somewhere of guitar and i dont' know where is the other end. It's deep inside cavity somewhere where i don't have access to. The other end is NOT seen in ANY other guitar cavities. It's not possible to touch the other end. I have no trust if this wire is actually grounded. It could be but it could also not be at all. If i don't need to ground this wire i would rather not use it as it don't trust it to be honest, hence my question if it NEEDS to be grounded to the rest of the circuit? Maybe this wire is the problem in this circuit?

What if that wire is lose and not connected to anything, meaning other end is not grounded anywhere. If i don't connect this wire will this still work with other grounds or it will NOT work?

The switch brand is switchcraft. This is the diagram for it. The bottom two connections are connected as that's + positive lead where top is negative ground lead. Right leg is neck pickup. Left is bridge pickup.

I've used this video for help but i didn't use shielded cable like he did. Doing the wiring outside i don't think would work as you can't fit those pots threw guitar cavity, however the pots where done outside just like he did.

I'm just NOT understanding where this circuit is failing. Currently it shows O.L which means no connection so not sure what to measure, where with multimeter. If i knew i would do some testing but i'm clueless as to where to start measuring.






« Last Edit: October 22, 2019, 06:48:41 pm by Rango »
 

Offline alsetalokin4017

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Let us please start with the mystery wire. As I said, this wire is supposed to connect through the guitar's body to the bridge mounting studs and tailpiece, to ground these parts to the rest of the circuit. I can show you videos of guitar makers installing this wire, but it would be simpler for you just to check.  Check for continuity between the free end of this wire and the bridge and/or tailpiece.
The easiest person to fool is yourself. -- Richard Feynman
 

Offline alsetalokin4017

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OK, with that particular Switchcraft switch, referring to that diagram, the two terminals on the bottom should be connected together and then to the Tip (+) of the Jack. The top left and top right switch terminals should be connected to the center terminals of the two volume pots respectively. The center top terminal of the switch connects to ground.

I think.

In that diagram the red and green lines show the connections made inside the switch when in the various positions, these are NOT wires you are supposed to add!


« Last Edit: October 22, 2019, 07:51:49 pm by alsetalokin4017 »
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Offline alsetalokin4017

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Quote
I'm just NOT understanding where this circuit is failing. Currently it shows O.L which means no connection so not sure what to measure, where with multimeter. If i knew i would do some testing but i'm clueless as to where to start measuring.

This is why I think you should start over from scratch, doing one part of the circuit at a time, checking with multimeter to make sure it's right, before going on. At the present time I can't even tell if what you actually have assembled corresponds to any of the circuit diagrams. So I don't know what to tell you to check!
First thing would be a good visual inspection to make sure you have it physically connected up right. Strong lighting, move stuff out of the way if necessary, take pictures, closeups, etc. Use a magnifying glass if you have to!

The easiest person to fool is yourself. -- Richard Feynman
 
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Offline alsetalokin4017

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Here's a video showing the Bridge ground wire installation.
skip to about 2:35
The easiest person to fool is yourself. -- Richard Feynman
 

Offline Rango

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Thank you so much. Ok i have done complete rewire. I think problem was on switch i had positive soldered onto negative and negative soldered onto positive. Anyhow i can now measure pickups at jack of the guitar. Also one of the grounds copper wire had poor connection or cold solder. I also fixed that.

However there is something odd here. When pots are at max volume 10 it registers 8.4k in neck and 14.4k in bridge, however when i turn pots down to middle it will actually show weird value like 40k ohms, and even something like 132k ohms. The middle when both pickups are on it reads at max volumes of both pots 5.0k ohms.

I'm pretty sure that's not normal unless 50s wiring and .022pf cap is doing this. I don't know what to make of that. I will post pics shortly. I'm tired troubleshooting this. I've been at it for 2 full days lol

Also i've done continuity on that ground wire and you ware correct it's connected to bottom log of tailpiece. For now i've tape it off with electrical tape as i'm not trusting it yet.
« Last Edit: October 23, 2019, 01:49:18 am by Rango »
 

Offline alsetalokin4017

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Thank you so much. Ok i have done complete rewire. I think problem was on switch i had positive soldered onto negative and negative soldered onto positive. Anyhow i can now measure pickups at jack of the guitar. Also one of the grounds copper wire had poor connection or cold solder. I also fixed that.

However there is something odd here. When pots are at max volume 10 it registers 8.4k in neck and 14.4k in bridge, however when i turn pots down to middle it will actually show weird value like 40k ohms, and even something like 132k ohms. The middle when both pickups are on it reads at max volumes of both pots 5.0k ohms.
Actually that sounds pretty normal. In the middle you are getting a combination of the pickup and the pot resistance, the proportion of one going up and the other going down as you turn the knob. Your values are similar to what I just measured on my Ibanez.
Quote

I'm pretty sure that's not normal unless 50s wiring and .022pf cap is doing this. I don't know what to make of that. I will post pics shortly. I'm tired troubleshooting this. I've been at it for 2 full days lol
It's normal. I think you have got it hooked up like you want it now. 
Quote
Also i've done continuity on that ground wire and you ware correct it's connected to bottom log of tailpiece. For now i've tape it off with electrical tape as i'm not trusting it yet.

I trust it. Just go ahead and solder it onto one of the pot bodies or another convenient ground point. This assures that the tailpiece, bridge, strings and headstock tuners are all grounded (connected by the strings themselves.)

Now string it up and see if it all works!
« Last Edit: October 23, 2019, 04:37:02 am by alsetalokin4017 »
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Offline alsetalokin4017

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Ah... you don't have a guitar amp yet do you. Guitars can sound funny/weird/broken when amped through other kinds of amps, due to the weird impedance mismatch. So you really won't be able to tell how it sounds and if it is 100 percent working until you can try it with an actual guitar amplifier.
The easiest person to fool is yourself. -- Richard Feynman
 

Offline Rango

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Ah... you don't have a guitar amp yet do you. Guitars can sound funny/weird/broken when amped through other kinds of amps, due to the weird impedance mismatch. So you really won't be able to tell how it sounds and if it is 100 percent working until you can try it with an actual guitar amplifier.

Many many thanks to you and all that helped me. I will ground that wire too. Didn't know you need to ground the outside of it too. Will do.

Luther will need to install the nut and do full setup, as i took old plastic one out as guitar would not stay in tune. Got the Tusq nut, locking grover tuners and rolling bridge as well. That should do it.

If the old nut would not be cut on weird angle i would do it myself but i don't want make things worst by filing. I'm thinking of Boss Katana 50 as it's fairly cheap but may try Amplitube 4 with audio interface first as those i have already.
 

Offline alsetalokin4017

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Yep, changing out the plastic nut, (and saddle on acoustic guitars) is probably the single most cost-effective thing you can do to a guitar to make it sound better and be more playable. I put buffalo bone nuts and compensated saddles on acoustics and it is amazing how much better they sound than with the old plastic bits. If you are a real note-bender, the rolling bridge, and the Tusq nut will help for sure.  Personally I think locking tuners are a step too far, like belt plus suspenders, but yes, good high-ratio Grovers are da kine.

Just one more thing to check: the Tone controls should not affect the resistance readings at the Jack at all. The tone capacitors function by sending high frequencies to ground, removing them from the signal, and the tone pots control how much. Capacitors don't pass DC current, and the multimeter is using DC current to measure resistances, so the caps look like open circuits no matter where the tone pots are adjusted. Neat!
« Last Edit: October 23, 2019, 05:17:33 am by alsetalokin4017 »
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Offline Rango

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Yep, changing out the plastic nut, (and saddle on acoustic guitars) is probably the single most cost-effective thing you can do to a guitar to make it sound better and be more playable. I put buffalo bone nuts and compensated saddles on acoustics and it is amazing how much better they sound than with the old plastic bits. If you are a real note-bender, the rolling bridge, and the Tusq nut will help for sure.  Personally I think locking tuners are a step too far, like belt plus suspenders, but yes, good high-ratio Grovers are da kine.

Just one more thing to check: the Tone controls should not affect the resistance readings at the Jack at all. The tone capacitors function by sending high frequencies to ground, removing them from the signal, and the tone pots control how much. Capacitors don't pass DC current, and the multimeter is using DC current to measure resistances, so the caps look like open circuits no matter where the tone pots are adjusted. Neat!


Thanks for that tip. Yes i noticed that. I played with tone knobs and it didn't do anything to resistance reading at all. I forgot to mention that as i was more concerned with what volume pots are doing. lol.

BTW do to this forum i bought Uni-T multimeter. I love that think and it was $40.
 


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