Wiring posts allowed??

[old_picker]

Got a problem with the wiring in a guitar I am finishing up.
Not really wood related but is a critical part of finishing an electric instrument.

Is this an appropriate topic for the musical instruments forum?

I bet some of you posters have good electronics unlike my remedial wire it and see if she goes approach.

[Iain]

Oh c'mon, don't keep us electronic junkies in suspense, this is barbaric, torture, what's the problem??????
Oh the agony..............

[old_picker]

Ok here goes.
p90 Megahum
Just wired her up and the hum is real loud I mean like something wrong with the circuit loud.
I have wired up two tele projects with vintage single coils and they are both real quiet. Nothing like the noise this lil mother is putting out. I expected a bit of hum but this is ridiculous. As p90's are pretty hefty I figured the hum would be negligible.Pretty standard wiring which I got off guitar electronics website. Tone on both p/ups and a master volume. Sorta guessed the earths. That side of it works perfect. The caps on the tone controls are .022's the pots dimarzio 500k. Pickups are Seymour duncan vintage p90's. Standard epiphone SG style sideways toggle switch.

http://www.aargent.com.au/postings/posting_pix/bh_wiring_p90.jpg

As you can see the control route is shielded. the p/up cavities are not.
The bridge p/up has no surround & fits snug into its rout with no room for foil. I could do the neck cavity and see if that does something but it dont sound like that is the problem. There is a fair amount of pickup [externaly braided sheilding] wire loose in the cavity [green lines] everything else is pretty neat and tied off


http://www.aargent.com.au/postings/posting_pix/P90.jpg

[Malibu]

Two things that I can see might be a cause, but it's hard to tell...

1) all the caps I've seen/used have been .047's, but that shouldn't contribute to the noise.
2)You might try earthing the other end of the volume pot. It's possible it's picking up stray hum from somewhere.
Hope it helps

An afterthought.. You earthed the bridge as well?

[rhoads56]

Add an earth wire to the bridge posts and it will stop humming.

[watson]

G'day,
Are all the hot wires shielded and the shield attached to ground??
I only ask, as your diagram doesn't indicate that.

And if its a "how do you suck eggs" post from me..I'm sorry (but put the hole in the blunt end of the egg)...smirk
Regards,
noel

[Iain]

How do you earth an egg???????????:D

[watson]

Under your foot usually

Regards,
Noel

[watson]

I should have said "eggsactly" (smirk)

[Iain]

I suppose you think that is some sort of a yolk:rolleyes:

[old_picker]

Actually further investigation reveals the volume contol is not working. It is acting more like a presence control.

The wires from the pickups to the switch are shielded but from there they are not.

Oh and no need to apologise for giving basic and to you ovious info. As i said trouble shooting basic wiring is a mystery to me.

Earth the other end of the volume pot? do you mean earth the third tag that is not connected to anything?

I never bothered earthing the bridge in the teles I built and they are very quiet with the shielding i used. Teles are usually pigs to keep quiet. I didnt bother with a chanel to earth the bridge. Besides when I touch the pickup poles with a licked finger it dosn't make much difference at all.

I got a feelin that when the volume is working properly it might come right.

By the way the guitar sounds like smokin' in hell. It's gonna be a hard one to send on its way when the time comes.

[watson]

Tee Hee!
Hope the old picker gets his hum fixed , as its usually the simplest thing that will fix it.
Whoops incoming!

[watson]

G'day Old Picker,
Good info there......if it where me, I'd shield from the controls out to the jack as well to be sure, but if the volume's acting like a presence control I'd also check the capacitor to the volume pot wiring, particularily the earthy side of the volume control
Regards,
Noel

[watson]

Just went back and checked your wiring diagram....if that's exactly as is wired, try wiring the bottom terminal of the volume control to the case or the sheild. It would appear if that's as wired, then the volume control doesn't have an earth reference and it would hum like hell.
Regards,
Noel

[old_picker]

Just went back and checked your wiring diagram....if that's exactly as is wired, try wiring the bottom terminal of the volume control to the case or the sheild. It would appear if that's as wired, then the volume control doesn't have an earth reference and it would hum like hell.
Regards,
Noel

mmmm
There is no cap on the volume pot and not in the source schematic either.
I use a .047 on the tele's between the vol & tone.
the volume pot isnt earthed.

As you and earlier poster said it should be earthed as shown on source schematic.

By the way to those calling for the "earth the bridge" solution I avoid that If possible. I saw one guy do a double back flip over his amp that busted him and his guitar up bad....he had his hands on a mike that was live [240 volts] and the other on his bridge - yes - bang - 240 volts followed the path of least resistance...The funny part about it was the audience thought it was part of the show and wanted us all to do it. What we did do was walk off and cancel the show. I bet plenty of you have had a nip from a live mike before.

I am gonna take the advice of shielding the hot wires, earth that vol pot and hopefully it will wotk normally. Will post back results and pics of the guitar when I get it right

[watson]

Too true,
Sorry about the hurried post of the capacitor to the volume control, I was in a real rush, and meant the tones, but finally got the message right when I had a good look at the diagram.
Hope it all works out..would love to see the results.
Regards,
Noel

[Malibu]

....he had his hands on a mike that was live [240 volts] and the other on his bridge - yes - bang - 240 volts followed the path of least resistance...

I haven't done anything with mic's so I'm not real sure about them apart from the theory of operation, but how could a mic become live to 240V?

Back to the post... Try the SD website, there's plenty of schematics there that might help
http://www.seymourduncan.com/support/schematics.shtml
:)

[kiwigeo]

Ihow could a mic become live to 240V?



Really green Roadie plugged it into a wall socket :D

[Paul B]

http://www.guitarnuts.com/index.php

Great info on wiring and sheilding, reducing hum etc.

[Malibu]

A good site Paul, one I'd forgotten about..
I had a long read on the shock hazard with mic's etc and what they say makes sense in that it all boils down to faulty equipment/wiring/supply. There's so many 'earths' in home audio and stage PA's that it's pretty easy to have one become loose through a connection or faulty solder joint.
Unfortunately all you stage muso's can't control the outlet where you plug in, you've got to trust the electrician (or the otherwise dodgy bloke) that put the outlets in.
There's a lively discussion here on the pro's and con's of DIY home wiring, with the rules and regulations discussed, which runs through a similar vein. Check it out if you're interested...
http://www.woodworkforums.ubeaut.com.au/showthread.php?t=41628

[JupiterCreek]

Hi

Your Tele does have an earthed bridge, unless you've cut the wire. If you look at the brass plate on the bridge pickup you'll see the wire goes from the coil to the baseplate. The pickup mounting screws go through the bridge and the brass plate, so there's your earth.

Is one of your P90's reverse wound / reverse polarity? If so it should be hum free in the middle position. Just the neck and bridge pickup on their own will have a smidge of hum but once you start playing that'll drown out any hum.

[old_picker]

Neither tele has an earthed bridge. I built both and didnt put a earth strap from the bridge on either. Both of them were very quite

The p9o's do sound quieter with both p/ups on. Currently I am redoing the hot lines with shielded [braid] wire and using more of a star grounding with the earths. IE all earths running to a commom point in the cavity and then to the jack.

Updated wiring pic
http://www.aargent.com.au/postings/posting_pix/bh_wiring_p90.jpg

Any further comments gratedully received.

[JupiterCreek]

Your Tele doesn't need a separate earth strap, it's built in, unless you've cut the wire link.

I recently built a Tele style tenor guitar for someone in Canada... customs decided to undo the bridge screws so he had to reassemble it with some help from me. To cut a long story short he kept on about the hum and popping noises, so emails went back and forth checking that the black wire on the Tele bridge pickup having the little solder link to the brass plate, the earths all being good, all the normal stuff. He mentioned at one point that when he put his hand on his mike the humming from the guitar stopped. I suggested he check the earths on his powerpoints... his electrician came to look and is coming back to rewire the house... none of the power outlets in his house have earths of any kind!

Back to your diagram.... are the tone pots working? I usually run the caps from the centre lug of the tone pot to earth, with the outside lug of the tone pot wired to the opposite outside lug of the volume pot. I have to confess to never having wired anything with one volume and 2 tone pots except Strats, for which I use Fender's Jimmy Vaughn setup. I've attached that diagram and anothe one for wiring two P90's. I know they're not exactly what you want but hopefully they'll be of some help.

[old_picker]

I guess that says it all about earthing a bridge.

I have just finished rewiring the p90 project and will check it out for hums tomorrow.

I sheilded the pickup cavities, ran coax on all the hot leads and grounded everything to a central point in the control cavity. Then it goes to the earth of the output jack.

That's the way I did the teles and it worked fine with no bridge to earth wire.

Will post back with the results and hopefully some pics.

[JupiterCreek]

Hi again

While you were posting I'd edited my post... sorry.

Re the Tele earth, I've attached a pic that shows that little link wire on Tele bridge pickups. It's actually a great idea provided you also have a fairly standard neck pickup.

Anyway... fingers crossed your wiring's fixed and hum free. Everyone should have at least one guitar with P90's.

[contrebasse]

none of the power outlets in his house have earths of any kind!

reminds me when I was sent to Hanoi in the 90's to troubleshoot a $250000 computer video editing installation in the local tv station purchased by an english NGO to make an HIV-awareness soap opera.

Nothing worked properly. Then when I was 'round the back of the machines my bum happened to touch the wall while I was plugging in video leads. Got a spark :eek: Then I tested the chassis of the vidotape deck ($85,000 digital betacam) and found it 240v live. No earths anywhere! When I asked why not I was told simply that it costs 30% more to wire earths and no-one in vietnam can afford it.

nonetheless, when I had the electrician run a wire from the power board to a piece of rusty reo outside in the garden, everything worked ...

[old_picker]

Well I done all the extra work on the hawk junior's wiring and it never made a scrap of difference. So I strung a piece of wire from the bridge and hooked it round the jack chassis and it shutup.

So now I gotta cut a hole from under the bridge to the control cavity BBRRR!!!:(:(:(

here she is and you can see what I am up against with getting that hole through.
You can see the earth hanging off the schaller roller bridge.

http://www.aargent.com.au/postings/posting_pix/hawk_jnr.jpg

[rhoads56]

Well I done all the extra work on the hawk junior's wiring and it never made a scrap of difference.

... and very very rarely will...


So I strung a piece of wire from the bridge and hooked it round the jack chassis and it shutup.

... sometimes its best to not second guess years of guitar manufacturing. Bridge grounds are there for a reason... they work! :)



So now I gotta cut a hole from under the bridge to the control cavity BBRRR!!!:(:(:(

here she is and you can see what I am up against with getting that hole through.


Buy a long drill bit. Simple!

Guitar looks good, lets see more of it.

[JupiterCreek]

I bought a set of "aircraft" drills on eBay.... they range from 1/16" to 1/4", they're 12" long, and the whole set was about US$20 or so.... absolute bargain!

But in your case I'de be drilling from under the bridge to the back pickup cavity. I just drill the hole anywhere under the bridge, then use a Dremel to cut a groove from there to one of the screw holes. Bare 1/2" of the wire, poke it in the screw hole, then tuck the wire into the groove. The wire doesn't need to be anything special. Light hookup wire is plenty heavy enough.

[old_picker]

I have a 1/4 x 12" bit which I did exactly as you said.
It's always scary for me cutting a hole like that. I used a piece of sticky copper foil under the bridge screws and the lighting wire I used had plenty strands so I just fanned it out over the foil and one of the screw holes. Tightened it down and checked the bridge to the jack chassis with the multimeter for resistance. I got a 0.