Wiring & Bridge help needed

[Aussiephoenix]

Hey guys,

since Im not quite a soldering-Iron-hero, I'd like to hear your input about 2 problems I'm having after recently having replaced the preamp on one of my basses with a new OBP3.

I'm having 2 problems:

1) the Blend pot isnt working properly... at each of the extremes, I have the full output of one of the pups, but in the center position, they seem to cancel out, having 0% output.
Did I wire it wrong? I tried to follow the scheme that came with the preamp... Or maybe the center detent pot I used isnt what I needed...

2) if I raise the trebble and mids, I get a fair bit of static in the sound... now, usually with say, a jazz bass passive harness, you've got the earth points joined on the back of one of the pots, but following the diagram, this doesnt happen. instead all the earth wires converge at the jack entrance (the spot without connectors for the jack). so, I have all the pots earth wired to that, and I have one other wire coming from the bridge, which I've connected to that as well.
Something else I should have done? or didnt do? (the pot cavity's grafite spray shielded, came like that.)


Additionally, and this has nothing to do with the preamp...

I changed over the gotoh-type bridge for a Schaller 2000 bridge as I've a fondness for those bridges, so used the existing holes (and added 2 more as the new bridge has 5 screws instead of 3.)
when I restringed and tuned the bass, I tried to set the intonation at the 12th fret and I've got a bit of a problem...

the Low B string saddle is full back, and it intonates perfectly as is, at the 12th fret. the other saddles progressively go forward to intonate perfectly too... the last 2 saddles, the D & G, are fully extended and they are still sharp at the 12th...
doesnt seem right... there wasnt that much of a difference in saddle position on the Gotoh bridge... something's off here...

thanks in advance for your help.

Edited December 4, 2007 by Aussiephoenix

[BOD2]

Not sure if I can help here but I'll give it a try.

Firstly I'm assuming you've got a good wiring diagram. There's one [url="http://www.aguilaramp.com/pdf/support_wiring_obp3.pdf"]here[/url] if you don't.

The OBP-3 is quite tricky to wire up as there are so many wires involved. Also, when I did mine, at least one of the wires was a different colour to that suggested in the diagram. Process of elimination eventually sorted that out.

Yes all of the earths go to the barrel of the jack socket. That's the part that protrudes out of the jack socket - the shell (sleeve) of the socket if you like. There should be two sprung contacts inside the socket. One (the ring) takes the black wire from the battery connector and the other (the tip) takes a green wire from the preamp.

I found I couldn't physically connect all of the earths to that point so I soldered a metal washer onto a short piece of wire, connected the end of the wire to the earth point of the socket, then connected all the earths to the washer. Then - very importantly, wrapped insulating tape around the finished washer so that no bare wires could touch anything else. Note that the earths from the pickups should also come to this earthing point - they're not shown on the wiring diagram.

Check and double-check the wiring of the blend pot. The "hot" wires from the pickups connect one each to the centre pins of the blend pot. Then there are two short "jumper wires" connecting the diagonally opposite pins from each layer in the pot. Finally, one wire goes to the master volume pot. The pots are shown from the rear in the diagram (the shafts pointing away from you).

Make sure there are no short "whiskers" of wire touching anything they shouldn't as this would short out the circuit and change its behaviour.

If you can see nothing wrong, try sending an email to Aguilar and describe the problem. They might be able to help.


As for the bridge. Hold the old bridge above the new one so that the mounting holes line up. Does the back edge of the new bridge fall roughly in the same place as the old one ? Have the bridge pieces got the same amount of travel ? If they don't then it might be necessary to remount the bridge using different holes.

Hope this helps.