A/P,P/A Electronics

[alvin986]

Hi...here's the thing...i made my Yamaha BB615(active) to passive.
All works well,but now when it's time to sell it i can't get the electronics to work(Active).
Problem : I wired everything right (white wire to in-s,black wire to in-g and red wire in bat on the input of the PCB,and on the output i soldiered white wire to out-s and black wire to out-g) on the out side of the PCB i have wire going from the PCB straight to the Volume pot and in side goes from Pickup select pot.When I put the battery in i get sound for a second or so and then nothing (degrading slowly from 100 % to 0 %).Anyone know why?
I can't find the picture of the preamp on the web,and on the PCB says Yamaha QCB7550.

 

[luknfur]

Hi...here's the thing...i made my Yamaha BB615(active) to passive.
All works well,but now when it's time to sell it i can't get the electronics to work(Active).
Problem : I wired everything right (white wire to in-s,black wire to in-g and red wire in bat on the input of the PCB,and on the output i soldiered white wire to out-s and black wire to out-g) on the out side of the PCB i have wire going from the PCB straight to the Volume pot and in side goes from Pickup select pot.When I put the battery in i get sound for a second or so and then nothing (degrading slowly from 100 % to 0 %).Anyone know why?
I can't find the picture of the preamp on the web,and on the PCB says Yamaha QCB7550.

FWIW:

My guess is it's not's wired right cause it's the most common outcome of such a scenario. A detailed diagram should have been made before the pre was removed and stored in safe keeping. Don't know the preamp but I do know that battery hot doesn't go to the PCB in for any pre I can recall working with. Sound source (pickup) goes to pre in through whatever chain that entails. Battery hot goes to PCB power supply - typically red also.

 

[alvin986]

Hi
I didn't put it anywhere,it was in my bass and i wrote which wire is connected where.On the PCB i have BAT,in-s,in-g for input and out-s and out-g for output.That's all.I have bat HOT goes directly to the preamp and GND wire goes to the output jack.That's how it was...I suspect on the Capacitor, i'll buy a new one today and change it,let You know the progress.

 

[luknfur]

Hi
I didn't put it anywhere,it was in my bass and i wrote which wire is connected where.On the PCB i have BAT,in-s,in-g for input and out-s and out-g for output.That's all.I have bat HOT goes directly to the preamp and GND wire goes to the output jack.That's how it was...I suspect on the Capacitor, i'll buy a new one today and change it,let You know the progress.

Sounds like you did what you were supposed to do - which is more than I can say of myself in earlier days. Control bay is the ideal place for the diagram but most guys cram them full of electronics.

If the pre worked fine when it was pulled it should work fine now. I still say odds are there's a wiring issue of some sort. Not impossible but highly unlikely anything's gone south in the pre since it was pulled. Much more likely it would have taken a hit and damaged while sitting in a drawer.

This thread may be useful

http://www.talkbass.com/forum/showthread.php?t=276127

 

[alvin986]

Well...I've done anything i could think of and still nothing...Bought a new capacitor,nothing either...checked the wiring...bass works fine on passive(even better if i can say),i just remembered 1 thing...a couple a weeks ago i unscrewed my bridge.Could it be that the GND doesn't have a solid contact?

 

[luknfur]

Well...I've done anything i could think of and still nothing...Bought a new capacitor,nothing either...checked the wiring...bass works fine on passive(even better if i can say),i just remembered 1 thing...a couple a weeks ago i unscrewed my bridge.Could it be that the GND doesn't have a solid contact?

The cap was a shot in the dark. The bridge thought doesn't flow cause ground is to the jack not the bridge. The pre would function without a bridge ground at all (EMG tells you to NOT connect the bridge ground) but may introduce noise if not used.

There's a link to a Bass mod guide in that trouble shooting guide that suggests possible alternatives to your situation.

Also the trouble shooting guide tells you how to check your bridge ground.