Author Topic: help- bad background hum returns.. (Read 8606 times)

sambo · « **on:** February 08, 2006, 09:59:10 PM »

well when my mate initially fitted my p-90 without the tap there was a nasty background hum which we managed to fix somehow (cant remember how exactly). then when i got the push/pull pot he unsoldered everything and fitted the tap.... at first everything was fine with a tad of background hum which was to be expected.... played it today though and theres nasty background hum which increases as i turn the volume on my guitar up. also the hum is twice as bad when the pot is pulled out....

another thing... the way its been wired, everything works except the actualy normal tone control doesnt do anything as in when you turn it nothing changes...

final little thing which may or may not be connected, theres a little separate, higher pitched and quieter fuzzing noise in the background unless my fingers are touching the pickup or bridge/tailpiece whatever...
my first thought= grounding problem... this could be the same problem for the bad background hum as well..

i have three theories:

1.) the wires that make the normal tone control work arent connected and cause hum
2.) a grounding wire has come loose
3.) its been wired wrongly in some way....

what does everyone think?

PhilKing · « **Reply #1 on:** February 09, 2006, 01:13:32 AM »

it sounds like you have disconnected the gound somewhere. The tone should work in all the switch positions. I have attached a diagram. The only difference is that the switch is on the volume pot. The wiring is the same either way.

sambo · « **Reply #2 on:** February 09, 2006, 08:07:50 AM »

thank you so much phil!!! thats perfect... did you do that yourself? if you did thanks even more for taking the time to do so lol.

PhilKing · « **Reply #3 on:** February 09, 2006, 11:24:32 AM »

I modified a diagram I got on the web. Guitar Electronics is a good place to look if you need standard (and some not so standard) diagrams. THey had one for a HB with coil tap, so I changed to match your P-90.

sambo · « **Reply #4 on:** February 09, 2006, 05:07:49 PM »

ahhh cheers mate... thing is now... to get all that done... im gonna have to take my guitar to my mates for a THIRD time to get it all done.... !!!

one thing doesnt quite add up though- ive got four wires from my pickup and the diagram only shows three (well a a fourth one is cut short).

on mine the green is the wire for the tap, black and a silver screen wire go to ground, and white is to hot. which is which in the diagram?

Tim · « **Reply #5 on:** February 09, 2006, 10:21:32 PM »

Like I said, ignore that short wire, it goes nowhere.To all intents and purposes you've got a start-black, finish-white and green for your tap.

sambo · « **Reply #6 on:** February 09, 2006, 10:28:07 PM »

ok cheers tim... yer i know to ignore the short red wire on my pup but in that diagram phil posted theres a fourth wire thats cut short....- so basically it doesnt add up- my pickup has 4 wires and a cut short one, the diagram has 3 wires and a cut-short one- a wire is missing the diagram...?

sambo · « **Reply #7 on:** February 09, 2006, 10:34:35 PM »

ok im really sorry guys... this has got stupid now... im so frustrated!!!!!

even with the diagram i cant make sense of things....ive searched on the web... im simply out of my depth even with detailed explanations... and on top of that i cant get a good picture of the wiring to post on here because i have cr@p cameras which make everything dark and almost invisible! ARGH!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

im completely stuck and feel like breaking something... have no cash to get it done at a shop and wouldnt anyway because its a rip off and i cant do it myself and i dont know anyone who can.... for god sake

:x :!:

PhilKing · « **Reply #8 on:** February 10, 2006, 01:03:07 PM »

Hi, there are 4 wires + screen in the diagram. The screen is the silver (it is labelled 'bare or shield'). If you swap the green for red, you should be fine.

The wires in the diagram are red - tap (so use green), white - hot, black and screen - ground, and green - not used (yours is red).

I updated the diagram for you.

sambo · « **Reply #9 on:** February 10, 2006, 04:01:37 PM »

thanks phil... for now im gonna have to get it done at a shop though

i have no soldering iron and it'll be the third time that ill have bothered my mate to try and help me if i ask him again ...

but next time i get a pickup that diagram will definately come in handy- im gonna try and wire them myself in future to avoid these stupid prices that shops charge... i think the main reason why i didnt really understand was the fact that we removed all the wirings in the first place without taking note to remember where they were supposed to go.... that meant that when we tried to fit the new pickup we were completely lost and didnt know which wire was which....

anyway like i said that diagram will make my life a whole lot easier- thanks mate. :D

sambo · « **Reply #10 on:** February 10, 2006, 08:33:50 PM »

dude just looked closer at that diagram and i think i actually understand it!!! problem now is my dads already taken my guitar to the shop

ah well.... perfect for next time... thanks again dude for the excellent help..

sambo · « **Reply #11 on:** February 11, 2006, 08:27:10 PM »

this is stupid... the shop (according to that diagram and explanation from you which i trust more than stupid Machinehead Music) fitted my pickup wrongly..... where the two rows of three are... the green (tap) wire is in the middle not on the outside/inside like you said it should be and in fact the outside of the three tags has no wire there at all!!!!????

well heres a really bad paint drawing of what theyve done...

the thick black wire on the left is the pickup wire out of which come the green (tap) wire, the white (hot) wire and the ground wires (black and silver) in a piece of rubber casing which is the thick grey line. the white wire goes to one of the outside tags on the volume pot, the ground wires in the casing go to ground on the volume pot and the green wire goes to the middle two tags on the tone pot. off the volume pot theres also the wire to the bridge. also, soldered to the same point as the pickup ground wires is a wire that goes to a capacitor and then to the input jack- the capacitor seems to be connected to the outside tag on the bottom of the tone pot by a small red wire (which is the red line on the diagram). the blue line is a wire going from the same tag as the white wire to the central tag at the bottom of the tone pot. the third black wire goes from the central tag on the volume pot to the input jack. the final wire is a small silver one that goes from the two outside tags on the tone pot to the bottom of the tone pot!?!?!?!

dunno if that makes any sense to anyone its pretty hard to explain... anyway its easy to see that its very different from phils explanation.!!!

PhilKing · « **Reply #12 on:** February 12, 2006, 02:07:09 PM »

They have wired it wrong. The white and green should go to the switch. I have corrected the wiring. Go to them and show them this and get them to fix it for free! They should be able to work out the wiring if they are serious tech's (i had no diagram with mine - I just checked the DC resistance to figure it out).

I used dark green and dark grey for the change. Orange is a new wire.

sambo · « **Reply #13 on:** February 12, 2006, 02:11:20 PM »

ARGHHH!!!! ok thanks phil...

so the orange wire is a new wire that goes to the middle two tags on the switch to the volume pot... does it go to a tag on the volume pot or just soldered on top?

and the grey one from the bottom/outside tags on the switch - is that meant to be the white/hot wire??? sorry its a poorly done diagram by me- the white wire was supposed to be the one represented by two thin black lines which goes to the volume pot, the grey one was the ground wires in some casing....

PhilKing · « **Reply #14 on:** February 12, 2006, 02:28:37 PM »

Sorry, fixed it again!