STK-S4n installed now getting hum

[donaldr]

I remove the Screamin Demon from my MIM Fender Strat, move the STK-7 to the bridge and install a new STK-S4 neck. Incredible match now for rock, pop and blues.
Here's the guitar:


But now I have a problem with hum. It's getting better when I touch the screen so looks like a grounding problem but I cannot find it.
I have a wire from tremolo clamp to the neck tone pot and black/bare wires are also going to the neck tone pot.
Here's the wiring (not as clean as I would like but a tech just passed before me...):

Any idea?

 

[shadowfire90]

Re: STK-S4n installed now getting hum

with grounding there is a few places to check

make sure the input jack is in the right places. sleeve ground , think SG , like a Gibson SG. Sleeve is metal to the base of the jack
tip is plastic at the base

two other ways to look for are
make sure the color code is correct. Hum can occur from series out of phase, its a weird 2 wire telecaster like tone you get out of just about any 4 wire pickup
make sure if a pickup has a coilsplit wires on a pickup if you have the option are soldered together and taped off
only do a single path to and from the string ground , going back for a second lap (lets call it) is bad for the wiring and will cause grounding issues

View attachment 102519

 

[GuitarDoc]

Re: STK-S4n installed now getting hum

make sure the input jack is in the right places.

I'm sure you meant "output jack", as labeled in the diagram.

only do a single path to and from the string ground , going back for a second lap (lets call it) is bad for the wiring and will cause grounding issues

Not quite sure what you're talking about here, but if you are referring to "grounding loops", forget about it. That doesn't happen in guitar wiring. Any ground path is fine, even multiple redundant paths are fine. They are unnecessary but won't hurt anything.

 

[donaldr]

Re: STK-S4n installed now getting hum

As I mentionned, the guitar was working well before I moved the pickups. So basically:
1- Removed the Screamin Demon: unsoldered it from the bridge tone pot, cut the black/bare wires from the top of the neck tone pot (ground)
2- Unsoldered the STK-S7 white wire from the neck tone pot, solder it to the bridge tone pot (didn't touched the black/bare wires on the top of the neck tone pot)
3- Solder the STK-S4 white wire on the neck tone pot and the black/bare on the top of the neck tone pot (ground)

Wire from the bridge clamp is soldered to the top of the neck tone pot.
Output jack black wire soldered to the top of the neck tone pot, red wire to the switch.

 

[donaldr]

Re: STK-S4n installed now getting hum

Could it be a defective pot?

 

[GuitarDoc]

Re: STK-S4n installed now getting hum

Could it be a defective pot?

Possible, but probably not.

Make sure none of your wires are touching anything they're not supposed to. Some of your wires look pretty close. You could also have a cold solder joint.

I would clean everything up in there...resolder every wire/connection. Make sure your iron is powerful enough (at least 40 watts but preferably 60-80 watts) to get the pot hot enough to make the solder flow like water, but for only a few seconds.

 

[donaldr]

Re: STK-S4n installed now getting hum

I have a digital soldering station, it's at 480 degre right now (don't know if F or C), what is the equivalent in watts?
Yep, I think I will resolder the tone pot. I also have to take a look at the volume pot, I can only goes from 10 to 7, lower than that it's unusable (CTS 250k audio pot).

 

[jeremy]

Re: STK-S4n installed now getting hum

that doesnt sound right, audio taper will roll off quickly from 10-7 but it should still make sound at 2. 480 C is super hot (890 F), 480 F (250 F) might not be hot enough.

whats the middle pup? i had a stks4n, stks4m, stk7b setup and loved it

 

[donaldr]

Re: STK-S4n installed now getting hum

Yes Jeremy, rolls quickly from 10-7, after that I still have sound but not a usable sound like on my LP where I can clean up everything until 3-4. Even my LTD Strat with vintage output (5.75k) pickups I can roll it down to at least 5 and get a good clean sound out of a crunch sound at 10. Not the case with the STK-S4-S&, they are really hot and don't clean up well.
Middle pickup is dummy, no plugged.

 

[jeremy]

Re: STK-S4n installed now getting hum

5.7k is pretty low assuming #42 wire but thats beside the point. my set of stacks cleaned up fine and sounded very nice with 250k volume and tone. do the tone pots work correctly?

 

[donaldr]

Re: STK-S4n installed now getting hum

Yep tone pots are working well. Maybe I should try a linear volume pot.
I'm playing with the pickup height right now. Normal that the STK-S4N is almost flush to the pickguard and the STK-S7 close to the string (maximum I can get with the tubing/screw) to balance volume wise? I really like that combination and the middle position (neck + bridge) is really good, ala Telecaster I presume (as I never got a Tele).

 

[Mincer]

Re: STK-S4n installed now getting hum

Those heights don't sound like the pickups are wired correctly. Have you tested them with a meter?

 

[jeremy]

Re: STK-S4n installed now getting hum

my pups werent far off those settings. the stks4n was set pretty low and the stks7 was set pretty high. the vintage hot stack isnt that much hotter than the stks4b, its less toppy though.

 

[donaldr]

Re: STK-S4n installed now getting hum

my pups werent far off those settings. the stks4n was set pretty low and the stks7 was set pretty high. the vintage hot stack isnt that much hotter than the stks4b, its less toppy though.

Ok, good to know that I'm not that far. Thanks.
I will definitely try a linear 250k volume pot next week while I'm on vacations. Going from 10 to 7 to almost nothing is not what I want.

 

[donaldr]

Re: STK-S4n installed now getting hum

Those heights don't sound like the pickups are wired correctly. Have you tested them with a meter?

Nope. Pretty basic wiring. Each pickup to its own tone pot, to 3-way switch, to output jack. My LTD ST-213 is almost like this too: neck pretty low and bridge pretty high. Maybe it's just me not used to pickups in Strats

 

[donaldr]

Re: STK-S4n installed now getting hum

I measured from top of pickup to top of string (E=.050): 19/64 for STK-S4n and 15/64 for STK-S7b, so only 1/16 between both. Now they are at equal (perceived) volume.
I will cut the STK-S7 tubing a little when I moved them to my LTD ST-213 to test having the bridge closer to the strings.
I have to admit a STK-S7b is really a balanced match to a STK-S4n.

 

[jeremy]

Re: STK-S4n installed now getting hum

glad you like the set, i really did too. not sure about the hum though, my set was quiet

 

[GuitarDoc]

Re: STK-S4n installed now getting hum

I have a digital soldering station, it's at 480 degre right now (don't know if F or C), what is the equivalent in watts?
Yep, I think I will resolder the tone pot. I also have to take a look at the volume pot, I can only goes from 10 to 7, lower than that it's unusable (CTS 250k audio pot).

480 would be "F". not "C".
There is no equivalent in watts. Watts is a power rating and has nothing to do with temperature. A 5 watt iron can get as hot as a 100 watt iron, but it can't maintain that heat while soldering. It will cool down significantly and give you cold solder joints because the solder and metal are sucking the heat out of it before it can regenerate the heat (enough heat to keep the metal hot enough to make the solder flow onto it like water). A high wattage iron can maintain a constant temp better, even when soldering to the back of a pot with lots of ground wires.

 

[donaldr]

Re: STK-S4n installed now getting hum

480 would be "F". not "C".
There is no equivalent in watts. Watts is a power rating and has nothing to do with temperature. A 5 watt iron can get as hot as a 100 watt iron, but it can't maintain that heat while soldering. It will cool down significantly and give you cold solder joints because the solder and metal are sucking the heat out of it before it can regenerate the heat (enough heat to keep the metal hot enough to make the solder flow onto it like water). A high wattage iron can maintain a constant temp better, even when soldering to the back of a pot with lots of ground wires.

My soldering station temperature is controlled digitally and stays pretty stable when soldering.
Getting back to hum, I removed the pickguard last week, to see if anything touching, replacing and no hum since. Maybe 2 wires were touching.

 

[jeremy]

Re: STK-S4n installed now getting hum

glad its fixed!