Strat pickup volume problem -- advice please

[Colin Brown]

I recently switched out a 250k volume pot on a strat. The problem is that the customer has voiced a complaint that since he got the guitar back he has noticed that he gets very little volume from both the low E and D strings on the neck and middle pickups ONLY. The bridge pickup is a JB jr. and that picks up the signal and sounds terrific through an amp. Acoustically the guitar sounds just fine which is what makes me think that the problem lies somewhere within the electronics.

This guitar has two tone knobs and only the one master volume knob. I am far from an electronics expert but have a basic understanding. That being said, is it possible that somewhere there is a bad ground connection that is causing these two strings to find their way to earth faster than finding the output jack? I was under the impression that treble, not bass, generally "bleeds" off first.

I see some suspicion in the fact that the two problem pickups are the only ones that have tone controls, but I am also hesitant to find a problem in the tone controls due to the fact that only two strings seem to have volume issues.

The guy is bringing the guitar back tomorrow and my plan of attack is to check all connections visually and then with a meter.

Any advice regarding this issue would be very much appreciated!

Colin

[Tom Krebs]

Are the pole pieces too close to the strings? That can create a problem. Roll the bass side down a notch. Some Strat pickups work best at a slight angle - treble side higher. I don't think the wiring harness would create such a problem.

[Colin Brown]

Pickups are set to factory specs: 1/8" bass side, 3/32" treble

[Tom Krebs]

It would be the first thing I would check. Next would be the strings. Factory spec is just a starting point. Listen to the pickup as you move it up and down. Some of those magnets can affect the string vibration and create minor tonal havoc.

[Colin Brown]

Right on. I was pretty sure I did a bit of moving the pickups around the first time I worked on it. But it seems as though I may have done something wrong so I suppose I might as well start with the most obvious.

Thanks for the pointers Tom

[Len Biglin]

Hi Colin, I'm an electronics tech and a luthier , electrically speaking if the pickup is working on some strings ok , then it's connected. The tone pots will only roll off the higher end of any string . So it comes down to the interplay between string and pickups , I was thinking perhaps he has replaced all the strings except E&D but then the JBjr is OK ! As Tom says you can get some wierd problems if pickups are too close to strings , I guess you need to see the guitar , check if the strings are running directly over the poles , and the relative height of the poles .Is the guy playing through a pocket size amp? Do the strings sound equal acoustically/no amp ?My feeling is that the guy is imagining it .Len

[Russell Vance]

I'm with Len on this one - I have not come across anything like this problem with Strats and as they are relatively immune to slight string spacing variations it's unlikely that the spacing is a problem. Change the strings for a new set regardless of anything else.

String pull due to the bass side magnets exerting pull on the heavier ferrous mass of the thicker strings is a definite problem and you would be well advised to set it up as per the factory specifications (not to make it sound good but to demonstrate to the customer that this is what Fender advises). Having the pickup poles too close to the bass strings causes a disonance (a warbling tone) on all pickup selections.

And, one thing - the JB Junior can be used with either a 500k or 250k pot - if the original pot you changed out was a 500k and you put in a 250k you would get a significant drop in output and the tone would become mellower in the bridge and bridge/middle selection - this would account for him saying things sound weaker (but not in the middle/neck and neck position). I'd put in a 500k pot on spec anyway as it makes the instrument cut more with a tougher attack.

Short of that tell him to have his ears checked. Rusty.

[Colin Brown]

Thanks for the input guys.

Is there any way that thepole pieces can come loose from the magnets? I'm really just kind of shooting in the dark here, because I did hear the guitar after I changed out the pot and the E and D strings were both signifigantly quieter on both of the stock pickups neck and middle positions - so I incorrectly assumed that it was like that when I got it because I really didn't do anything signifigant to the guitar.

Rusty - The reason I changed the pot in the first place was because he had a coil splitting push pull pot and it wasn't comfortable for his playing technique. Since you responded to my post I have checked the push pull pot that was in the guitar and it is a 250k.

I suppose I'll change the strings, mess with the pickup heights, and if that doesn't solve it tell him to think about investing in some new pickups?

And if he doesn't go for that I guess I'll just have to tell him that I'll take the guitar off his hands free of charge.

[Russell Vance]

Umm, OK, I assume from what you said that the pickups are of the ceramic bar type (a flat magnet under the "slug"pole pieces) and not the traditional Strat with the magnetized pole pieces.
If it has the magnetized pole pieces without the bar magnet on the bottom of the pickup you could certainly start checking whether the pole pieces under the weak strings had lost their magnetic strength (which can happen for a number of reasons, shock or heat or a stray magnetic AC field will do it - but its difficult to see how two pickups could have lost their magnetism in two poles exactly the same). If it has a ceramic bar magnet and slug pole pieces the likelyhood of it being a magnetic disparity is low.,

Additionally, you could check the pickup pole height stagger (if these pickups have the staggered height pole pieces as on traditional Strat pickups) - these pole heights can be changed. But, this left field stuff - I'd change out the pickups with a known good pair and try to isolate the problem that way. But, firstly, change the strings to a new set if it hasn't already been done. I'm running out of places to go with this problem - but would really like to see it through, any additional help of thoughts? Rusty.

[Colin Brown]

Rusty,

I am not entirely familiar with strats, but I do believe that it has traditional strat pickups, which would contradict the question that I asked about loose pole pieces. Regardless, I didn't pay too close attention to the pickups when I did potentiometer work the first time because, honestly, I wasn't doing anything to the pickups, aside from the humbucker.

Also, I was under the impression that traditional strat pickups had pole pieces that weren't adjustable?

In regard to changing out the pickups, I will have to talk to the customer to see if that is something he wants to do, seeing as I don't have any interchangable pickups on hand - this is a part time repair shop I am running after going to school for luthiery and so I am still in the beginning stage of the learning process.

I do genuinly appreciate the advice.

Colin

[Russell Vance]

Ah, yep, the pole pieces are adjustable with a press and pin - they are an interference fit in the plastic bobbin and simply pressed in. You can adjust them if the string to string balance needs tweaking (such as going to a wound third from a thick plain) but it's unusual to do so, and a delicate operation anyway.

Now, if the Strat has a 'swimming pool' (large rectangular route for the pickups as opposed to the conformal three slots routing on traditional ones) cutout you may wish to reverse one of the pickups in question - ie; put it in rotated 180 degrees and see if the weak strings move with the pickup orientation, this may assist in determining where the problem lies.
These problems are the type that make you tear your hair out, regardless of your level of training....I keep a draw full of 'known good' electronics and pickups to change out after the logical and deductive troubleshooting has run out of road!
Good Luck on this one, Rusty

[Colin Brown]

Rusty,

So I've got the strat here at the shop and I've changed the strings and messed with the pickup height. The problem is still there. So, I disconnected the 5-way selector and hooked the neck pickup directly through the volume pot and restrung it back up, results: Low E string is near dead and the D string is also dull sounding, the rest of the strings are fine. I then did the same with the middle pickup and had near identical results. Following that experiment I then changed out the pot with a 'known good" pot and the results were the same. I also checked the DC resistance of both the neck and middle pickups, and they measured 5.8K. To me this says that the pickups are no good, or at least a couple of the pole pieces are demagnetized.

I find it strange that both pickups are behaving in the exact same way... The biggest concern I have is that it's something I have done, and I haven't done anything except change out a pot -and I'm sticking to my guns on that one. The guy said that he has had a lot of trouble with this guitar from the get-go and this is the third time he has had electronic work done. I'm going to suggest that he put new pickups in the thing.

I have no idea how they could have become demagnetized but it really does appear to be what has happened in this instance. Are demagnetized pickups something you come across very often? Just in doing some research on the internet it seems to be a pretty rare occurance.

Thanks again, Colin

[Ron Frazier]

I am not a electric guitar fan and I have learned my lesson in working with the wireing.

I have haad sodder joints thwt look good but are called cold sodder joints. It comes from blowing on the hot sodder to make it cool faster.

NEnt the pickup needs to be at the neck farther away from the string and the bridge can be closer.

Is it a real FENDER or one made in a foregn port. Pickups are very cheep!! We buy those pickups for 2 or 3 dollars and a real Fender is like $90. 00--to $150.00 . If you put in the better ones get rid of the wiring that is too small to carey the signel.

Ron