ASAT wiring and 60 cycle hum

[anteriorl5]

Wired my ASAT body last night, plugged it in and had a nasty hum. Clearly a bad ground, I ripped out the grounding plate in the bottom of the control cavity and soldered the grounds to the volume pot. That helped, and the guitar is quiet with both pickups on but too much noise neck and bridge. Is there extensive shielding from the factory? Do i need to line the cavities with copper? Even twist all the grounds together before soldering to the volume pot? Run a jumper between the pots? Your help would be appreciated.

[guitar_ed]

I always jumper the pots. I thought it was SOP.

edg

[Craig]

Wired my ASAT body last night, plugged it in and had a nasty hum. Clearly a bad ground, I ripped out the grounding plate in the bottom of the control cavity and soldered the grounds to the volume pot. That helped, and the guitar is quiet with both pickups on but too much noise neck and bridge. Is there extensive shielding from the factory? Do i need to line the cavities with copper? Even twist all the grounds together before soldering to the volume pot? Run a jumper between the pots? Your help would be appreciated.

See this in our Gallery: Album: ASAT Wiring Schematic (all years).

And, don't forget tthe ground to the bridge.

Hope this helps.

[anteriorl5]

Tore it all apart, rewired it using the G&L schematic, even tried a different jack. Same hum. Just not grounding properly or picking up an unusual amount of EMF. Shielding next step I suppose. 4-way switch - may try a 3-way to simplify.

[Craig]

Tore it all apart, rewired it using the G&L schematic, even tried a different jack. Same hum. Just not grounding properly or picking up an unusual amount of EMF. Shielding next step I suppose. 4-way switch - may try a 3-way to simplify.

Perhaps this post will help you toubleshoot your hum: Shielding Test?.

Hope this helps.

[anteriorl5]

1st position, neck pickup I get hum. No noise touching the neck pickup. Dead quiet in the 2nd position, 3rd position I get a pronounced buzz and a static noise when I touch the pole pieces of the neck pickup. 4th position same static touching the neck pickup and loud buzz. So when the neck pickup is off, I get a loud hum/buzz. Hum is cancelled in 2nd position. do i have a bad neck pickup ground at the coil/baseplate? The solder connection looks good there. I'm using the SC-2/asat 4-way wiring diagram from this site. Wondering why the ground wire from the neck pickup (green wire) goes to the switch and not to ground.

[Tooslowhand]

Was it quiet before you rewired it? Probably just me, but I am not familiar with a 4 position configuration on the ASAT. All of mine have a three position switch. Maybe it is for parallel-series of the two pickups. If there are plates or parts of the pickups that need to be grounded and you connect them to other than ground due to the switch wiring you can get bad hum, or no output. An example is the metal cover on a standard Telecaster neck pickup. It is connected to the return wire of the pickup and needs to be grounded. If you want to wire a series-parallel configuration with this pickup the cover needs to be disconnected from the pickup return wire and grounded separately, as the neck return gets connected to the bridge hot in a series humbucking configuration.

Also, if you have other single coil guitars are they quiet or noisy because it could be something in your house? I had my old Fender amp serviced and when I got it back every single coil guitar I tried to play through it caused a lot of hum, that went away in the middle position. The tech was very reputable and swore the amp was dead quiet after he worked on it. I took it to a studio and sure enough, no noise at all. I could never figure it out and just left a great old amp with a cover on it. A year later I changed all the CFL recessed lights in my house to LED. For no particular reason at some point I tried the amp again. Dead quiet.

[anteriorl5]

Since it's an "Oak Grigsby" switch, I'm going to rewire it exactly as Stew Mac has it drawn out. Seems there are 4 or 5 different ways to wire these switches. Different cap configurations, etc. I'll keep after it until I get it right. This guitar has never been together, but I am comparing it to my other guitars through a '62 Deluxe that is quiet.
5/31: Studying the two drawings, I see that the Grigsby diagram has the neck hot going to switch, and the SC-2/ASAT diagram has the hot going to the volume pot, as I've got it wired. Back to the soldering station...
5/31: Have checked everything: New jack, tried different pickup, tried separate grounds on the baseplates of pickups, etc. Now dead quiet neck and middle position, bridge pickup noisy alone and series with neck. Just makes no sense unless the switch itself is bad.
6/2: Cut the nut today and it sounds great and dead quiet. Love the vibrato. First G&L with vibrato as my 2000 S-500 was a custom order hardtail.

[anteriorl5]

Ditched that 4-way and wired it up to a 3-way I had from a Telecaster. It is now dead quiet in all 3 positions and sounds fantastic. Love the MFDs. They are quite a bit different from the smaller S-500 pups in a very good way.