Doubleneck wiring woes

[runtfan]

Greetings all,
I am building a 6/12-string doubleneck, and just got the wiring done last night.  I've wired a few guitars with no problems in the past, and am pretty comfortable with a soldering iron.

I'm more or less copying the Epiphone version of the EDS-1275 (which has a separate pup switch for each neck).  I looked around and found a few wiring diagrams, but ended up "doubling" Seymour Duncan's "Two Humbuckers, 1 Volume, 1 Tone, 3-Way Switch" diagram and connecting the hot leads to a third 3-way switch.  I mangled the diagram to show how I did it:

Note - I did NOT connect the green & bare wires from the pups to the pots.  I connected them to the ground on the pup switches, and connected THAT to the pots, so the picture isn't entirely accurate.  And I only had .22mF caps available, not .47mF.  But the tone seems OK.

In all, it works, but there are a few minor problems that I'm hoping someone here can diagnose.
1. Lowering either volume pot affects both necks.
2. When both necks are active, the output (volume) is significantly reduced.  I imagine this is related to #1.
3. On either neck, there is a lot of hum unless both pickups are active.  I figure this may be a grounding issue, but putting my hand on the bridge has no effect.

I wonder if there's a better way for me to wire the guitar...  Please let me know if you need more information.  Thanks in advance!

 

[tfarny]

You need to first off swap the ins and outs on the volume pots - as described here: http://www.stewmac.com/cgi-bin/hazel.cgi?action=SERVE&sku=i-4000&PG=4&s1=Free_info_sheets&item=freeinfo/fi.html And while you do that, make sure both your sets of pots are working off the same lugs - the mirror image thing below is cool but the reversed lugs on the pots confuses me.

Second, that sounds like a nightmare to ground, you must have a real rat's nest in there, and you probably are missing a ground. Consider grounding everything to one common lug - for instance screw a little eyelet into the side of the cavity, throw some solder onto it, and just attach all the grounds there, sending one wire to the jack and another to the bridge. You don't need to 'ground the backs of the pots' - the backs of the pots are just traditionally how it's been done. Check the picuture to see what I mean. Besides looking neater it'll be easier to spot grounding issues. Hope that helps.

 

[runtfan]

You need to first off swap the ins and outs on the volume pots - as described here: http://www.stewmac.com/cgi-bin/hazel.cgi?action=SERVE&sku=i-4000&PG=4&s1=Free_info_sheets&item=freeinfo/fi.html And while you do that, make sure both your sets of pots are working off the same lugs - the mirror image thing below is cool but the reversed lugs on the pots confuses me.

Forgive the hasty photoshopping.  The volume pots are wired the same for both necks, not reversed as in the picture.  But thanks for the info - that's what I was missing!

Second, that sounds like a nightmare to ground, you must have a real rat's nest in there, and you probably are missing a ground. Consider grounding everything to one common lug - for instance screw a little eyelet into the side of the cavity, throw some solder onto it, and just attach all the grounds there, sending one wire to the jack and another to the bridge. You don't need to 'ground the backs of the pots' - the backs of the pots are just traditionally how it's been done. Check the picuture to see what I mean. Besides looking neater it'll be easier to spot grounding issues. Hope that helps.

It sure does.  My problem with one lug I think would be that the pickup wires for the top neck are not long enough to reach the control cavity.  I'll have to check it when I get home tonight.

Thanks again!

 

[mayfly]

a double neck!  cool!

so, does your camera work?

 

[DangerousR6]

You need to first off swap the ins and outs on the volume pots - as described here: http://www.stewmac.com/cgi-bin/hazel.cgi?action=SERVE&sku=i-4000&PG=4&s1=Free_info_sheets&item=freeinfo/fi.html And while you do that, make sure both your sets of pots are working off the same lugs - the mirror image thing below is cool but the reversed lugs on the pots confuses me.

Second, that sounds like a nightmare to ground, you must have a real rat's nest in there, and you probably are missing a ground. Consider grounding everything to one common lug - for instance screw a little eyelet into the side of the cavity, throw some solder onto it, and just attach all the grounds there, sending one wire to the jack and another to the bridge. You don't need to 'ground the backs of the pots' - the backs of the pots are just traditionally how it's been done. Check the picuture to see what I mean. Besides looking neater it'll be easier to spot grounding issues. Hope that helps.

Most definitely a better way to ground, lernt that trick from studying the wiring on one of my Jackson's... :icon_thumright: