YAMAHA TRB6 QUESTION

I have recently purchased a used Yamaha TRB 6 BASS ( only says TRB on headstock )
It has Yamaha active pick ups.
It also has a five knob configuration for adjustments all below the bridge area of the Bass.
There are 2 larger knobs, one I know is the volume.
Directly underneath are three smaller knobs.
I can't find an owners manual on this anywhere, and I am not EXACTLY sure what each knob does.
Can you offer any help?
Thanks!!!!!
Dick

 

Thanks to all for all of the quick responses.
The two upper knobs ( full size ) are definately volume & pick up selector.
The three smaller ones are from right to left while playing the bass:
1 - has three positins , but is a non - click position knob. You just feel center.
2- has three click positions
3 - has three positins , but is a non - click position knob. You just feel center.
There is no toggle, so that must mean no piezo I gather.
On the headstock it only says YAMAHA in smaller letters that run horizonatally across the very top.
The TRB-6 runs up the headstock between the string winders.
There is no P or PII.
I think it is one nice bass.
I jammed on it for about 5 hours today with some folks who really push the jam, and it feels a bit wide once you get up around the 9th fret, but it is amazing how quick one adapts to the neck.
In short order you learn to appreciate the six strings and the neck width is not an issue.
It is one VERY solid sounding instrument.
By the way the neck is two truss rod & 6 bolt- bolt on.
Glossy purple, wood grained finish - maple neck, rosewood fingerboard, gold ( brass ) metal.
On the BACK it has a set of directions for adjusting the on-board electronics,that is on the black cover over the electronics and knobs. High mid - low which I think I will leave alone as the instrument sound great, and I have no clue about the adjustments.
I have NOT been able to locate any serial # and it is not visible anywhere.
With that description can anyone give me an approximate date of manufacture, or if there is a serial # wwhere is it, and can I date it by that?
Thank again for the help.