Esh Hero mystery switch

[RattleSnack]

I recently aquired older Esh Hero IV (1996.), a very nice passive bass with Schaller pickups and hardware. It plays great and weights just 3,3kg (7,3lbs) so it could stay with me for a longer time.
But, controls are puzzling. It has master volume, tone and rotary switch. Switch has 4 positions, and they sound to me like: both pickups parallel, neck, bridge, both in series.
Since those pickups are, like DiMarzios, humbuckers, could neck and bridge positions be internaly series? And last position?
Here are some photos!

 

[line6man]

Draw it in schematic form. It's too difficult to make out what the switch is doing, from a picture, alone.

 

[Josh Thatguy]

Esh-bass.com has diagrams based upon pickup configurations, which would probably apply IF your bass still has stock pickups and wiring.
For my Stingers, the 4-position rotary switch is 1. piezo only; 2. Piezo/EMG MMTW blend; 3. EMG MMTW only; 4. Direct out/no tone or volume control, for running straight into a recording console or DI unadultered.

The Esh website is out of date, but the diagrams are there somewhere, and show different pickup configurations.
Cheers!

EDIT--- I just re-read your post and saw that yours is *passive*, so ineould venture that the 4-position switch does exactly what you've already thought of. While moving to different positions in the switch, tap each pickup very lightly with a key or metal cable-end while the bass is amplified, and you'll hear which ones are activated.

 

[Axstar]

There are resistors and caps (look like Wimas?) on the rotary switch. The resistor might be there to cut down on the 'click' as you switch through settings, but the caps will be doing something else.

Edit: The brown and white wires are the series link between each coil within the pickups. The pickups must be like Schaller's JBX (Dimarzio Model J clones) but with slugs instead of hex-screw pole pieces. I cannot understand why the green and yellow wires appear to be ganged together to terminals on the switch as these represent the start of one coil and the end of another in Schaller's setup.

 

[Stuart Hmm]

I think I've got a pretty good idea about your bass: years ago, I came across a Stinger bass with two Schaller JBX's. It had 4 controls: volume, tone & 2 4-position switches: one did what Josh Thatguy said, but the other one got me interested: its 4 positions were: bridge, both in parallel, bridge pup + passive midboost, both in series. Of course, the kid who worked there had no clue about electronics, raising the hood of a brand new bass in store was out of the question, and the next time I went to that store to check it with the owner, the bass was already sold. I really liked the bridge + midboost sound, since I could use that on my bass, but have no idea how is that achieved. I'd really appreciate a schematic of that !

 

[40Hz]

Looks like in addition to playing switching games with the pickups it's also switching in different tone capacitors. The one you can see in the photo is an 0.22. I'd guess the other is an 0.47

What might be happening is: neck only with the 0.47, both with the 0.47, both with the 0.22, bridge only with the 0.22. That would give you some pretty broad tonal variations with just one switch and two pots for controls.

 

[mech]

What I'm seeing for the caps and resistor, and this is a SWAG, the unknown to me cap at the side is a high roll off since one end is grounded. The .22uF cap at the top appears to be paralleled with the 3.3K, 1%, resistor and may be used as a high pass with some lows shunted by the resistor. If the signal were run through the paralleled cap and resistor it would act as a high pass/low cut and seem to be a mid "boost" although there would be no boost since there are no active components to add gain. This goes along with what @Stuart Hmm said. The 3.3K would set the level of the lows that bypassed the cap so there would still be some bottom end.

 

[RattleSnack]

Thanks everyone for your reply!

At the moment, bass is going for a fret dressing/setup, but I will draw a schematics when I can. As far as I know, wiring and pickups are original. I contacted Esh, but they can't help me - it is not the same Esh that made instruments in 90', so no support for me.

 

[Stuart Hmm]

Here's what old Esh site said about wiring: "... midboost achieved by switching signals from the neck pickup to the complete signal". Your comments ?

 

[RattleSnack]

Hmm (pun intended), maybe this is how they describe series connection?
Still waiting for my bass, luthier is taking his time.

 

[Stuart Hmm]

No, this was specifically about the bridge pup + midboost position. I managed to find some notes I took from their site after I played that Stinger bass, way back in previous century. I'm still curious how it's done.

 

[Axstar]

Hate to be that guy, but in a passive bass nothing can be boosted. My total guess is that the pickups are selected in series in one setting. The switch seems to utilise the series link for both pickups, so that might also have a part to play. If the pickups conform to Schaller's wiring colour scheme then the brown and white wires will be the link between and E-A and D-G coils in each pickup.