Pickup not showing DC resistance but still works?

[Edika]

Hi all, I just got a new (used) pickup, a Gibson 500T. I have one in my Gibson Explorer and really like it, so I got another one.
The first thing I do whenever I get a used pickup is to measure the DC resistance to make sure the pickup works. This is the single wire with the braided cover. I took out the multimeter but got nothing. I thought I was doing something wrong so I put it on the guitar I was thinking of and I got signal and sounded quite good, but a quite bit on the bright side. Which of not want I would expect from this pickup. I tapped both coils and they worked.
I thought I did something wrong with measurement. I tried it several times and I even measured the 500T in my Explorer and I got DC resistance. I opened the Explorer cavity and measured it and still got a measurement.

So it seems I have signal, so the coil wires seem to be ok but I'm guessing the ground is not working as the circuit is not closing. Would that be the case, can a pickup still work and give signal if the ground is not working? And if so, would that explain why it seems to be so bright? It doesn't seem to be more noisy than other pickups?

 

[odibrom]

Hard to tell from this side of the screen. Is it sounding like the other you have? Have checked its sound with clean amp settings or also with drive?... Are you confident to open up the pickup and check it out?

I'm not familiar with this pickup, is it covered?

 

[Edika]

Hard to tell from this side of the screen. Is it sounding like the other you have? Have checked its sound with clean amp settings or also with drive?... Are you confident to open up the pickup and check it out?

I'm not familiar with this pickup, is it covered?

I know it's difficult to troubleshoot through a screen but to answer your questions, it sounded a lot brighter than my other 500T. I had sound with the clean channel and the distorted and tapped both coils and was getting sound.
The pickup is not covered which makes things easier to open up and I have opened up pickups before. I tried to open this one up. One of the coils seems ok to come of but the other seems stuck and I don't want to put too much force before I'm sure that this is the problem. The braided wire has solder on the hole it goes through which makes things more difficult but I was hoping there was more leeway to open it up without desoldering stuff and removing the pickup tape.

I contacted the seller and he never measured the pickup. He said it worked well on his Les Paul before replacing it with a Bareknuckle. If I need to return it I don't want to do any intense surgery on it. The pickup tape Gibson is somewhat smooth and different from other pickups but quite brittle if I need to remove it.

 

[odibrom]

The different tone it has may be related to the rest of the circuit, namely the pots' values and tapper... I'm / we're to assume the rest of the guitars is similar (scale length, strings' gauge and tension and model/brand and age, guitar construction type, bridge...), right?

Is the pickup's volume/punch/attack different (as significantly lower or hotter) than the other?

Can you do a direct connection to jack (bypassing all switches and pots) on both guitars to test side by side both pickups?

 

[Edika]

The different tone it has may be related to the rest of the circuit, namely the pots' values and tapper... I'm / we're to assume the rest of the guitars is similar (scale length, strings' gauge and tension and model/brand and age, guitar construction type, bridge...), right?

Is the pickup's volume/punch/attack different (as significantly lower or hotter) than the other?

Can you do a direct connection to jack (bypassing all switches and pots) on both guitars to test side by side both pickups?

The guitars are really really different lol, so no comparison there. When I put in the pickup, I installed a Black Winter neck pickup too, and the difference in bass response was too much, I felt that the 500T had less signal but it was the difference in bass response. In the past, I had put the Black Winter set in my Explorer (that has the 500T/496R set stock) in the past to see if I like it more and the bass response was similar with the Black Winter bridge being a tighter and with a lot more clarity.
In the current guitar the difference in bass response between the Black Winter bridge and 500T was really big. I'll install the 500T on my Les Paul that is easier to do and see what it sounds like.

 

[odibrom]

Well, in different guitars the pickup response will be different, more so if the core specs are different (scale length, construction type, bridge type, strings condition, gauge and model) but they'll somehow show their colors. Do check the pickup's height (distance to strings) as well, since this little parameter has a lot of effect on how a pickup sounds.

Another thing you can do is to replace the pickup in the guitar that has its brother and see if the guitar sounds the same...

Pots have a huge effect on how a pickup sounds, small value differences do have a big effect, a 450k and as 550k ohm pots are in the same ballpark of the 500k and are generally marked as so, but the 550k will make the pickup sound brighter / more open. Different guitars, different pots... hence my previous suggestion for a direct to jack connection on both to bypass all other electronics...

Can the pickup exist in the market with different magnets? Some brands do that, sell a pickup with either Alnico or Ceramic magnetic bars (thinking Bare Knuckle)... can that be a thing? Nevertheless, it won't answer the lack of DCR value on the multimeter...

... and this is as far as I can go...

Could it have been bad contact with the pickup's leads and the multimeter's sensor needles? Sometimes there's (fingers') grease that won't allow the contact to happen but when the leads are soldered it goes away...

 

[Edika]

Well, in different guitars the pickup response will be different, more so if the core specs are different (scale length, construction type, bridge type, strings condition, gauge and model) but they'll somehow show their colors. Do check the pickup's height (distance to strings) as well, since this little parameter has a lot of effect on how a pickup sounds.

Another thing you can do is to replace the pickup in the guitar that has its brother and see if the guitar sounds the same...

Pots have a huge effect on how a pickup sounds, small value differences do have a big effect, a 450k and as 550k ohm pots are in the same ballpark of the 500k and are generally marked as so, but the 550k will make the pickup sound brighter / more open. Different guitars, different pots... hence my previous suggestion for a direct to jack connection on both to bypass all other electronics...

Can the pickup exist in the market with different magnets? Some brands do that, sell a pickup with either Alnico or Ceramic magnetic bars (thinking Bare Knuckle)... can that be a thing? Nevertheless, it won't answer the lack of DCR value on the multimeter...

... and this is as far as I can go...

Could it have been bad contact with the pickup's leads and the multimeter's sensor needles? Sometimes there's (fingers') grease that won't allow the contact to happen but when the leads are soldered it goes away...

I've tried the measurement several times and I get nothing. I'm getting something when I actually touch the needles somehow which would be my DC resistance lol! I tested the multimeter on other pickups and even on the 500T on my Explorer and it was working ok. I can probably try put the "new" 500T on my Explorer as a reference sound and try to match the height to be sure the response will be the same and see if the sound is different.

The specific pickup comes with a thick ceramic magnet and two thick ceramic flanks. I checked the magnets and they seem correct. If there was DC resistance being measured, it should be 14.5 KOhm. I'll try and do that this evening or tomorrow at some point and see how the two 500T's compare.

Cheers man and thanks for replying. It is a weird situation, where the lack of DC resistance would point to a dead pickup and that is what I was expecting when I put it on the guitar. But there was signal, not excessive noise but sounded quite bright from what I would expect from it. That is why I was thinking that maybe the grounding on the braid is not working and not closing the circuit for DC resistance. But then I was not sure if a pickup can function and produce signal without the grounding.

 

[bostjan]

Blown fuse in your meter? Probes not connected to proper terminals on meter? Meter not set to kohms?

 

[Edika]

Blown fuse in your meter? Probes not connected to proper terminals on meter? Meter not set to kohms?

None of the above as the multimeter gives regular readings on other pickups.

 

[oversteve]

If it works and is somewhat on the bright side compared to others it's possible someone moded it and added a capacitor in series somewhere inside the pickup as a high pass filter. That way it won't give resistance reading but will work fine.

p.s. SD invader neck pickup has similar desing with capacitor

 

[Edika]

If it works and is somewhat on the bright side compared to others it's possible someone moded it and added a capacitor in series somewhere inside the pickup as a high pass filter. That way it won't give resistance reading but will work fine.

p.s. SD invader neck pickup has similar desing with capacitor

That is something I did not even think about. Not sure if the previous owner had it in his guitar from stock or bought it second hand. He surely did not modify it. I'll see how it sounds on the Explorer tomorrow and if it is considerably brighter and not noisier, without giving a reading on the multimeter, then it might be as you say. Checking the coil where the braid wire exits the backplate, it seems like there's either solder or something else holding the magnet in place. I'll be curious to open it up but don't want to pry it loose in fear of damaging the pickup.

 

[oversteve]

That solder blob is holding the braided wire itself, you can try removing the tape around the pickup and look for a capacitor on the side where the braided wire is connected to small wires from the coils

 

[odibrom]

... you can try the disassemble the pickup's baseplate without removing the fabric tape around the bobbins. It is probably glued with the wax bath the pickup took. Don't forget to unscrew it first...

... and by how long this thread is going, we deserve a few photos already, right? ... guitar included because SS.org...

 

[Edika]

... you can try the disassemble the pickup's baseplate without removing the fabric tape around the bobbins. It is probably glued with the wax bath the pickup took. Don't forget to unscrew it first...

... and by how long this thread is going, we deserve a few photos already, right? ... guitar included because SS.org...

I probably need to heat it up a bit to melt the wax. I'll put it in the Explorer first and see how it sounds before performing surgery lol!

 

[odibrom]

I probably need to heat it up a bit to melt the wax. I'll put it in the Explorer first and see how it sounds before performing surgery lol!

On all the pickups I've opened, never needed to heat up the wax, in fact, I advise you not to do so because you might also melt the bobbins' wax and make the pickup microphonic... I'd carefully use a knife for leverage between the baseplate and the bobbins/magnets.

 

[Edika]

So I got impatient, as usual lol, and opened up the tape on the pickup. There are four wires as can be seen. The white ones should be the south of the first coils and the north of the second connected and the coil with the screws seem to have the black wire connected to the baseplate, giving the ground, and the black coil of the slug coil, which would be the south of that coil, is connected to the core of the braided wire. The braided wire being soldered on the baseplate should be connected with the black wire soldered on the baseplate from the screw coil and ground it.



I've only tinkered with 4 wire connected pickups but this seems on in terms of connections. At least I think it does. I'll try and solder in the pickup before I close it up again. The tape Gibson uses is one use as it's been covered with wax too. I have some pickup tape luckily but would want to see if the sound response I'm getting is similar to my other 500T. So I'll replace the one in my Explorer and see.

 

[Edika]

So I put it on my Explorer and it sounds really bright. It's really aggressive though lol. I matched the height of the pickups. It might be giving a bit of a lower signal or it might be due to the reduced bass response. I haven't completely dismantled it to check if there's any capacitor in there but it doesn't seem to be the case unless it's in between the coils, soldered with the two wires there. When I tried the multimeter while it was soldered on, the only reading I could get was the pot. I tried to connect the black wire that goes from one coil to ground and the other black wire that is the hot and still got nothing.

This is really puzzling as there is signal that is quite strong, there is sound coming from both coils indicating they are working, but there's still signal with no DC resistance. I got it quite cheap so I'm not that fussed to keep it but on the other hand it seems it's a bit more trouble than it’s worth. I did take of the tape from the pickup and the one I have looks more like the one you see in Duncancs so in a sense the seller can claim I mangled the pickup, if I return it and can't make it look like it was previously.

Or I can keep it and just try to fix it and use it. I can convert it into a 4 wire conductor cable instead of the braided wire.

 

[Randy]

Forgive me for skipping way ahead but bright with funky multimeter reading to me says one non functioning coil.

 

[Edika]

Forgive me for skipping way ahead but bright with funky multimeter reading to me says one non functioning coil.

Thanks for replying Randy, would that be the case if both coils make noise while connected to the guitar and being tapped?

 

[Randy]

Potentially yes, because both sets of poles/screws are attached to eachother through the magnet anyway. You could, to some extent, be hearing the 'working coil' when you tap on the non-working one.

It's hard to say. My first thing I'd say was your wiring is off but you tested it forward, backward, in and out so I'd assume you'd have caught a flub by now if that were the case. I only mentioned it because I recently did a rewire and the pickups sounded okay-ish volume but shrill and when I hooked the meter to it, it was reading near zero because a bridge on my coil tap made it so one coil was running back into the other one backward.