Stop Me Before I Kill More Pots!

[fngrpepr]

I'm on my maiden voyage trying to wire up a single coil pickup to 1 vol, 1 tone. I'm following this schematic:

So far, I've learned that soldering irons are hot and you shouldn't touch the tip with bare hands, and also that you shouldn't have to hold the iron tip to the pot for 30+ seconds to get the solder to melt (oops, old iron with corroded tip which I've replaced with a new iron). I'm pretty sure I killed the pots first time around since when I had it wired up the tone pot didn't do anything and I was getting strange background noises. Also, I had really made a mess of things with lumps of solder.

I decided to start over with new pots and some newfound soldering 101 knowledge. This time, it seemed things went better. However, when I plug 'er in, I found that the tone control still didn't seem to do anything, and further, when I turn the tone knob all the way down the guitar volume goes to 0. Any suggestions on what could be my problem?

[killemall8]

Dont know dude. that is a correct diagram... Either your leaving out a ground, or your cap isnt working.

[psw]

Hey there...the diagram looks ok but is missing the ground to bridge connection that can result in some noise...

But...killing post...a hazard...

Most make the mistake of trying to solder to the plain pot shell without any prp at all. These htings are machined and often have a residue of lube from making them or a coating or oxidization on it that resists soldering...

Simple solution...before soldering...get a file and file to a bit of shiny bare metal on the edge of the pot (away from the contacts is best and don't get filings inside them .

Then immediately, use rosin corred solder to "tin them" at that point...so make a nice solder bead where the filing is, you should find that it flows pretty well, it will take a bit more heat than ordinary wires.

Now...strip the wire and "tin" them to...get a nice solder coating for the join on the bare wire. Again, these wires need to be clean, so it's good to strip the wire, give it a bit of a twist of the strands and "tin" them immediately with just enough heat and time to get the job done...

If using bare stiff wire, again, a bit of sand paper will get the corrosion off...copper oxidises pretty fast...the solder will protect it ready for the join...

Only then...do you join the wire to the join...effectively all you have to do with these "tinned joins" is melt the tinned solder together...so you don't need to heat up the parts so much again, as the solder at the joins themselves that you have already prepared...the result is that they should just easily flow together and you will get a perfect join every time.

If you skip this "good practice" you may be successful, but you may find that the insulated wires melt, the joins are suspect or over heated and the whole thing gets frustrating!

This procedure applies to anything...circuit boards corrode/oxidize (look dull)...so a gentle swipe or two with some wet and dry light paper will bring them up to ready...old wires, better to cut off the daggy end and re-strip a little than just rejoin (shielded cable especially needs this as if it is corroded you might use more heat and burn through the insulation causing a short...clean wires attended to immediately is the key.

Hope that helps anyone with these kinds of soldering questions...if unfamiliar with soldering, there is a bit of skill in it...so practice on a few wires or something is the key...but it is not really "that hard" especially if you follow these kinds of techniques and don't treat the stuff as if glue!

Oh...yeah, looking after the tip is important...again, prepare, clean and re-tin the tip always at the end and frequently in use...this will protect it with a layer of solder.

Also, you do not need a big iron to do these things, even pots...small is definitely better. I now use a soldering station with soldering pencil and small tip...a bit of a cheat as it is thermostatically controlled and very light...but I have used bargain basement little irons with just as much success...it's just trickier to tell how hot it really is. One way is to have some test wires or pots about and test on them first, just before your join. A wet sponge can cool the tip down with a little "hiss" or indicate to the experienced how hot it is...you may well have to turn these things off for a bit from time to time and re-heat...without a thermostat it will just get hotter and hotter!

[Geo]

I don't think you're killing your pots. It just sounds like one of the connections on the tone pot is not good. It sounds like the tone pot is acting as a volume control. Pots do break of course, but usually only after lots of use. Your pots are probably fine--just double-check your circuit against the diagram, and follow PSW's tips on soldering. Luckily you have a very simple circuit, so it shouldn't take too long to find the problem.

[Paul Marossy]

I don't think you're killing your pots. It just sounds like one of the connections on the tone pot is not good. It sounds like the tone pot is acting as a volume control.

Yep, that's exactly my thoughts on it, too.

[Mender]

From the result you are describing, it may be that the capacitor lead that is soldered to the middle leg of the pot is shorting out against the body of the pot. You should have a short insulated sleeve on that lead so it cannot touch the pot body.

[Paul Marossy]

From the result you are describing, it may be that the capacitor lead that is soldered to the middle leg of the pot is shorting out against the body of the pot. You should have a short insulated sleeve on that lead so it cannot touch the pot body.

I thought of that, too. That would definitely make it act like a second volume control while doing nothing as a tone control.

[fngrpepr]

Thanks for all the tips and suggestions. I took another look at it tonight, and realized that the capacitor leg connected to the tone pot tab was also brushing against the back of the pot-- just as had been suggested above. I repaired this, and the tone control now appears to be working.

However, one thing I'm noticing is that there is a distortion type sound in the background whenever I play, maybe at about 10-20% of the note volume. It disappears when not playing, and doesn't appear affected by whether I'm touching the strings or not. Any suggestions on cause of that?

[ShadesOfGrey]

Thanks for all the tips and suggestions. I took another look at it tonight, and realized that the capacitor leg connected to the tone pot tab was also brushing against the back of the pot-- just as had been suggested above. I repaired this, and the tone control now appears to be working.

However, one thing I'm noticing is that there is a distortion type sound in the background whenever I play, maybe at about 10-20% of the note volume. It disappears when not playing, and doesn't appear affected by whether I'm touching the strings or not. Any suggestions on cause of that?

Do you maybe have a high output pickup or the height is maybe very near the strings?

What do you use to plug your guitar in? I have noticed that for example computers and a few multi-fx dont like high output signals.

Dont think it's that, but it could happen.

Or maybe theres some microphonics in the pickup?

[Paul Marossy]

Yeah, if you have the pole pieces of the pickup too close to the strings, you can get "stratitis". Read this page and see if it applies at all - http://www.riograndepickups.com/faq.htm

[fngrpepr]

I went over this more this afternoon, and I don't think the issue is pickup being too close to strings. If I take the pickup out and hold it above the strings so I can move it closer or further away, I notice that regardless of how close it is, whenever there is sound, there is this kind of harmonic distortion sound in the background. I've tried wiggling wires around and pushing on the soldered connection but no dice. Any further ideas?

[psw]

You have given no details about the pickup...

It sounds perhaps like a poorly potted or cheap pickup...the windings in the coil can vibrate at higher volumes or resonate creating it's own signals perhaps.

Have you heard this pickup in a guitar working before?

Other culprits can be the way the thing is mounted so that it could be vibrating...there are ways of dampening things down but it's hard to know what you are dealing with. If mounting on an acoustic for instance, the top will vibrate and so too the pickup mounted on it and can cause such problems...

I'm not sure of the value of the pots either, but if you have a high value (rather than say 250K ohms that say a fender would use typically) then you will be getting increased treble where this kind of thing hides...just a few thoughts...

"Strat-itis" particularly affects real fender style pickups with the magnets as the poles...but any single coil can produce these things if adjusted too close. The magnets pull on the strings in a narrow area that could be a harmonic and so dampen vibration modes at certain frets...plus, it can in fact pull the strings out of tune.

post some more details, even pics, maybe that will give some clues...

[Mender]

To check whether it is the pickups or the rest of the electronics that is causing the distortion, connect a jack socket directly to the pickup leads, and plug into your amplifier. If that cures it, then you have to add each electrical item one at a time until you find what is generating the distortion.

If, however, it doesn't cure the problem, then either the pickup is "poorly", or the amplifier has a problem. Can you try the guitar on a different amp, or a different guitar on your amp?

[fngrpepr]

Thanks for the suggestions guys. I'm making progress. I verified the amp and cord, went back and resoldered 2 of the connections, and the 'distortion' problem appears to be gone. I also just lined the electronics cavity with conductive tape I got from Stew mac, and also attached the bridge to ground, which I verified did appear to reduce hum. (I'm using a kent armstrong single coil and 250k control pots and a .05mf capacitor).

Now my only issue is when I plug in the cord, the sound will cut in and out if I wiggle the cord. I think the issue is a stray ground wire shorting the signal somewhere. So I have to go over everything this week and try to track that down.

I think my biggest mistake through this was in connecting the shielded cables. I should have stripped the shielded portion further back so I had more room to work with when soldering the ground vs the hot signal; one of the issues I was having was that the shield was shorting against the hot signal since they were too close together. Next time I'll know better and give myself more room to work with.

[Paul Marossy]

I verified the amp and cord, went back and resoldered 2 of the connections, and the 'distortion' problem appears to be gone. I also just lined the electronics cavity with conductive tape I got from Stew mac, and also attached the bridge to ground, which I verified did appear to reduce hum. (I'm using a kent armstrong single coil and 250k control pots and a .05mf capacitor).

Sounds like a case of a cold solder joint. Interesting that it can have that effect. I will store that one in long term memory.

I think my biggest mistake through this was in connecting the shielded cables. I should have stripped the shielded portion further back so I had more room to work with when soldering the ground vs the hot signal; one of the issues I was having was that the shield was shorting against the hot signal since they were too close together. Next time I'll know better and give myself more room to work with.

Yeah, that makes life much easier. Live and learn, eh?

[KeithHowell]

Sounds like a case of a cold solder joint. Interesting that it can have that effect. I will store that one in long term memory.

Cold solder joints and especially those that have bit of flux still in them can act like a semi-conducter and give a diode effect. Causing untold problems most often noise but can demodulate radio stations. Often the reason you get this in effects pedals or badly built amplifiers.

When I worked in the telecoms industry the analogue equipment was very prone to bad soldering especially the older tube/valve stuff.

Keith

[Paul Marossy]

Cold solder joints and especially those that have bit of flux still in them can act like a semi-conducter and give a diode effect.

Interesting. I've never heard of this in the eight years I have been on various guitar related forums.

[KeithHowell]

Interesting. I've never heard of this in the eight years I have been on various guitar related forums.

In the old days of crystal radio sets this effect was used to form the diode in the receiver. The "crystal" was a lump of something, can't remember the details now, with some impurities mixed into it. You scratched on the lump with a piece of wire,called a cats whisker, until you found a spot which gave you reception.

When valves/tubes were invented diodes became available and the need for the crystal and cats whisker fell away.

This is not first hand knowledge, I'm not that old, but we learnt a bit about the history of radio in Radio 101 at Technikon.

Keith