Yamaha AES820D6 - just can't understand the electronics

aja

My friend has the Yamaha AES820D6 baritone guitar with dual humbuckers.

http://www.yamaha.com/yamahavgn/CDA/ContentDetail/ModelSeriesDetail.html?CNTID=2517&CTID=

It has the following controls (as we understand it):

A three way pickup selector (top right)
A three position tone control knob (bottom left)
Bridge pickup volume (bottom middle)
Neck pickup volume (bottom right)

We read somewhere that the volume controls are (somehow) used to split the coils into single coil mode. This was also confirmed by the previous owner of the guitar, although he never elaborated on the exact method.

Now for the tricky part:

When the neck pickup is selected, only the neck pickup volume knob affects the sound. This is logical, right? The bridge volume knob does nothing and the tone knob functions as it should (although it is difficult to determine exactly what the three positions do, seems like "bass boost/mid scoop/treble boost").

However, when the pickup selector is set to either bridge only or bridge and neck pickups combined, the volume knobs appear to be wired in series and both need to be dialed in for any sound to be heard. Even when the bridge pickup is selected alone, the neck pickup volume needs to be dialed in or absolutely no sound is heard.

What is going on here?
And how exactly are the coils supposed to be split? (apparently the volume is set to anything below 1/2 to activate single coil mode)

aaarrggh... ???

MikeM

Dependant vol control. It's typical of dual vol pot guitars.

You can make it independant by swapping two of the lugs on each pot, but that's a bit of a hassle.

I have no idea how the coils are split. Are they not push pull pots? Perhaps give us a photo of it's guts ?

AlanRatcliffe

MikeM wrote Dependant vol control. It's typical of dual vol pot guitars.

Yup. Not a serious mod to sort out (IMO) - 5 minutes with a hot soldering iron. The two controls end up independent and less interactive.

I can't say for sure without looking inside or seeing a schematic, but I think your three way rotary tone switch is the coil tap. It is possible to tap with a pot (in fact it's very cool, you get to vary the balance of the pickup between humbucker and single-coil and anywhere in between), but to tie it in to the volume control would be very unusual, needing a very special (and thus very expensive) taper pot. Operation would be very weird however you arranged it. Anyway the service manual lists the pots as two bog-standard B500K pots.

So I'd put money on the three way tone control (not listed as a "tone" in the manual, btw, but as a 2-pole, 3-way switch) being the coil tap. The three positions will be humbucking, half-humbucking (via a capacitor, just the low frequencies are humbucking) and single-coil. To figure out which is which, plug in, turn up (not too much - this can be loud!), flip the selector to one or the other pickup and tap the polepieces of that pickup with a screwdriver while you flip the switch. Humbucking, both coils will sound the same. Single coil, one coil will be off. Half-humbucking, one coil will sound very bassy, with the tone rolled off. The switch will work on both pickups at the same time.

MikeM

Always gotta be that one step better hey Alan... ?

Nice intelligent reply, I gotta try and make mine more like that ?

Bob-Dubery

As far as I can tell the AES820D6 is an AES820 with a long scale neck.

You can get a manual. including wiring diagram, for the AES820 at
http://www.yamaha.com/yamahavgn/CDA/ContentDetail/ModelSeriesDetail.html?CNTID=2516&CTID=223450

AlanRatcliffe

MikeM wrote Nice intelligent reply, I gotta try and make mine more like that ?

Well, more verbose at least. ? I had to think about it a bit as I don't know the guitar, but figuring it out on the info given is a big part of the fun for me. Putting it into type is practice and helps me explain things better the next time I do so.

I see from the manual at the link Bob posted I was correct (assuming the two guitars share the same circuit). Interestingly though, Yamaha use two different caps for the half-humbucking, which I've never thought of doing. Goody - more to experiment with.

aja

Thanks guys! Will report back when we test all the new info!

Karma to everyone! ?