Help Wirring Bass Guitar on board preamp

[ilcaccillo]

Hi,
I'm repairing at the moment an Oakland & Co Bass. I'm having a lot of difficulties in trying to wire the active preamp circuit.
There's not much info around on these bass guitars, and no schematics.
The Active Bass preamp circuit uses 2 IC's, the TL064 and a TL061.
It seems a similar layout to a MEC bass preamp, although the MEC uses TL064 and TL062, couldn't find a schematic on the MEC unfortunately.

Someone in the past messed around with the wiring of the active circuit and some wires were cut also.

I did a reverse engineering on the circuit and drawn a schematic of it (attached) , with the color of all the wires that come out of the board.
I would like to ask if someone could help me out of point me in the right direction of where to connected the wires.
The active part has a DPTP 3 way switch and a Dual gand 56K Pot.
The passive part has an 250K volume pot and an 500K Tone pot. The passive circuit is wired and working (picture of the current layout attached).









I just don't really know where to connect the wires coming out of the preamp board and how to integrate this circuit into the passive circuitry already in place.

I know how to read schematics, and I'm able to build fx pedals and other audio electronic projects although I'm still learning and I don't know electronically how an amplifier, buffer or active tone circuit works. That's why I'm asking for your help.

The wires coming out of the preamp board have this colors:

Yellow
Green
White
Blue/Black
Grey
Black (ground connection to VOL Pot case)
Brown
Yellow Stripped (ground connection to Tone Pot case)
Orange stripped
Orange
Violet
Blue Stripped
Blue
Red (+Voltage from the Batteries)
PAD??? (pad on the pcb , it seems a wire was cut from here)

Some of them should connect to the 3 way DPDT switch (the switch that turns the active circuit on or of)
Others to the Dual gang pot
and the rest to the others part of the circuit like the pickup selector switch, volume pot, tone pot, output jack

The 3 Way DPDT Switch has already a Jumper soldered between 3 pins, picture attached.



It would be great if someone could have a look into the schematic and give some tips and direction

Thank you so much

Edited January 29, 2015 by ilcaccillo

[ilcaccillo]

I redrawn the schematic with Eagle and replaced the hand drawn one in the Above post.

Here are also some pics of the PCB top and bottom:


PCB TOP and BOTTOM pics:

Edited January 30, 2015 by ilcaccillo

[ilcaccillo]

[ilcaccillo]

It seems that IC2 is the input Buffer.
IC1B is most likelly and summing output unity gain inverting stage

IC1A, IC1C, IC1D seem to form a State Variable Filter

I re-drawn the schematic with a new layout, using the previous PAD??? as the input.

I re-traced the board also 2 times, looking for mistakes of my original tracing.
I found an important mistake there was a resistor missing, it's 2K Resistor and connects IC1B Pin6 to R12 and C5.
IC1D and IC1C were wrongly placed in the first schematic, they are swapped now.
And the C8 capacitor is 22nf and not 22uF.

I fixed all these mistakes in the schematic, it makes much more sense now, it's much clearer and easy to follow.

[ilcaccillo]

theres an Alembic Pramp that uses a similar State variable Filter topology to the one used on this Oakland bass preamp.
here it is the Alembic schematic:

[3below]

It might be worthwhile to look at the IC manufacturer reference designs for the TL064 and TL061 that will be somewhere on the internet. I would be surprised if the pre-amp designs deviate far from the reference designs. They might provide useful pointers or confirmation of what you have deduced so far.