"Hum" when volume is turned down on my Gretsch?

[John Cartwright]

First of all, Hi!  It's been a looong while since I last posted, but life is strange sometimes, and we have to roll with it.  Anyway, I'm glad to be doing more with guitars again, which brings me to my query.

I recently acquired a Gretsch G2622T Streamliner in a trade, and set about upgrading the electronics installing Gretsch HS Filtertron pickups. All has gone well, pretty much, but I've encountered a problem I've never dealt with before and have found little information online that would help me solve the problem.  I'm hoping someone can assist. 

I purchased all new components except for the switch, which include four 500k CTS mini pots, push-back Fender style wire, and Switchgraft jack.  I also fashioned platforms to mount the pickups that can be removed if need be.  I used this schematic and followed it carefully with the exception of the omission of the treble bleed.  

All solder connections are solid, clean and shiny, and the circuit was tested for functionality prior to installation.  I’ve tested the continuity of the ground throughout the guitar with a multimeter and all looks good.  The controls function and pickups respond as they should.  However, when I roll off the individual volume controls from 9-0 I get a terrible hum.  When the neck pickup alone is engaged and the volume is down it hums badly even at 0, as is true with the bridge volume when it is selected.  However, when both pickups are engaged and one pickup is on 10 and the other from 0-9, it’s fine!  But if a roll back the volume of the pickup formally on 10 in combination with the other from 0-9, then it hums badly.  The hum does not occur with the master volume.

I’ve noticed that the schematic calls for wiring the pickup volumes differently than the master, basically reversing the connections to the far left and center lugs.  This is different than the master and pretty much any guitar by Fender or Gibson that I’ve encountered. Could this be the trouble? The problem occurs plugged into three different amps both directly and through pedals and the hum is consistent no matter where I stand in the room. I just can’t seem to find the same scenario being described and remedied anywhere. I'm hoping someone here can help.

Many thanks!

[Mike Kolb]

If you don't get much 'action' on the issue here, John.... there's a great FB group that deals exclusively with electric guitar wiring issues.  It's a closed group but well-worth joining.  Good luck and let us know how it turns-out?

https://www.facebook.com/groups/333254887172028/

[John Cartwright]

Well, I'm not a FB user, Mike, but certainly appreciate your link.  I'll keep it in mind though.  I know this forum is a bit more focused on the more physical elements of repair and creation, but with such knowledge here I thought I'd give it a go.  Neck resets, re-frets, bracings, bridge fabrication I can get my head around, but electronics baffle me sometimes.  I love electric guitars, but sometimes when I see that soldering iron I think "oh boy, here we go!"- Ha!  Thanks again :-)

[Walter W Wright]

lots of guys over on TGP with a good grip on the electronics side of things (i like to think that i'm one of them!)

you're on the right track with the "reversed wiring" thing, that's called independent wiring and has a lot of drawbacks including tonal loss when turning down and leftover hum even on "0". that's why gibson doesn't do it that way.

the only point of that wiring scheme is to let you turn off one volume and still hear the other pickup, but if you have a selector switch then even that point is moot.

that said you shouldn't be getting loud hum when turning down, only a little residual leftover hum on "0". my first guess is still that the grounds aren't all connected; are you sure the third lugs on all the volumes are grounded to the casings? even then, the symptom there is usually that the volume doesn't turn all the way off.

it might be worth trying the neck and bridge volumes wired "normal" (pickup on 1st lug, output from middle lug) just to see what happens.

also, look for something "dumb" like the jack wired backwards or the switch lugs not wired right; that the problem happens on both pickups suggests it's downstream, somewhere in the common parts of the signal path. that would mean switch, master volume, master tone, or the jack.

[Len Biglin]

if you rewire the individual vol pots so that the pickup goes to the hot end and the output is from the middle , like the master , you should fix the problem . but the volumes will them interact a bit (like a Les Paul) If that doesn't fix it you may have your jack wires transposed .Also make sure your strings are grounded through the bridge or tailpiece .

[John Cartwright]

Fellas, thank you for your input!  I'll pull the guts back out and switch the wires on the volume pots as soon as a get a chance, and I'll double check the grounding/continuity and jack again too.  You are right, that anyone can slip up and reverse something now and then.  

I thought it odd that the volume pots for the two pickups were reversed like that, but I thought "hey, it's on the official Gretsch site, what could go wrong?"  I also saw the same on the TV Jones site.  Don't know, maybe it works for some folks but not so much for others. I did also look up "independent wiring" and found a lot of folks that are far from impressed.

Oh, I forgot to mention, the hum I was hearing was nowhere to be heard with a Strat, a Strat that thinks it's a Tele, a LP and a custom guitar I built some years back through the same rig, and all of which I wired myself.  Just for reference.

I'll report back soon as I go forward.  Thanks!!!

[Russell Vance]

Hi John,

Do yourself a favor and Google Ann Arbor Guitars, go to the "videos" tab on the main page and spend a couple of days getting your head around guitar electronics (including video tutorials on independent v master wiring).  David Collins is the main suspect and while he is much too busy  for forum work these days (as are a lot of us) his contribution to the guitar knowledge base and repair base along with his accomplices at A2 is outstanding.   His ability to cut through the BS and voodoo/folklore with live demonstrations of outcomes and findings is a breath of fresh air.

We use his knowledge on a daily basis and my customers regularly benefit from his teachings. 

Rusty.    

[Walter W Wright]

+1

i haven't seen all of them (not the "independent wiring" one at least) but those vids where david C demos the actual effects both graphically and audibly through his switching boxes are just fantastic.

you'll never bother with expensive magic caps in a guitar again

[Len Biglin]

John the idea behind the wiring of the pots is that when you have both pickups on , you can turn one of them down and the other one stays loud . So you are turning down the input to the pot not the output . The shortcoming of this system is that the jack remains at high impedance (flat out)  even when both of the pickup vols are turned down , meaning the output will attract noise . However the way the master vol is wired will lower the output impedance as you wind it down (less noise) . You can switch the wires in and out of your pickup vols. or use shielded wire (as in Les Paul) from the vols to the master and then jack . I'd do both , but just try swapping the 2 wires on pickup vol's 1st , that will fix it but when both pups are on the vol's will interact . This is the major diff .with Gibson v Epiphone Les Pauls , the gibson pots interact but are quiet , epi don't interact but ARE noisy if turned down .

[John Cartwright]

Thank you, this is all great information.  See above to Russelll's response for an update.  Thanks!

[Russell Vance]

Yep Walter, 

The David C capacitor test is a fun thing:  I'm thinking of selling tone enhancing,  hand bent,  genuine metal melted down from original PAF pickup cans "paperclip capacitor replacements" for $20 a throw on EBAY.   That'll be my retirement plan.

Rusty. 

[John Cartwright]

Yes, very well organized, concise yet detailed displays of these things in Collins' videos.  Thanks guys!

Though I must say I do like a little unicorn horn dust sprinkled on my caps for a livelier tonal response.  ;-). 

...but seriously, really good stuff you all are putting forth. Thanks!

[John Cartwright]

Update:  Well first let me thank all of you for your suggestions; I found them very helpful.  The David Collins videos were fantastic - really put a lot of things into plain English. ...I definitely need that! 

What I determined from further experimentation was that changing to a Gibson style wiring of the pots did not reduce the hum in this case.  In desperation for an answer I reached into the f hole with my finger and started pushing wires around and when I did the entire signal would cut out - absolutely no sound - then back to noise when released.The hum was coming from something touching something, but I could not figure out what. I decided to play it safe and order some Gibson style shielded single conductor wire and some more shrink tubing along with new pots just in case.  (That stiff Fender style wiring was stressing the lugs on the pots when in motion, it appeared.) I wired it all from scratch and I used the Gibson style dependent wiring, and the guitar functions properly and is now really quiet!  I never could figure out what was at the heart of it all, but at least I got where I needed to go in the end. I will say that the traditional wire used in Fender guitars is not the most easily wielded choice for a hollow body guitar - lesson learned there.  This might have been a player in the game.

Again, thank you all for your help and I do feel like I have a better understanding of things, though I will continue my journey into demystifying the electrical realm.  Thanks! 

Loving the Filtertron pickups in the Gretsch, by the way. Quadraphenia (The Who) and Love (The Cult) all the way!