Fried preamp?

[PhilT]

Is there any way of telling whether a pre-amp is working using, for example, a multi-meter?

Reason I ask is I have an OPB1 that I installed and it worked, then took it out, then tried to reinstall it and couldn't get it to work. I checked batteries and wiring, and it all looked ok, but can't get a sound out of it. Bass works passive, so I thought I may have fried the preamp while soldering, but I'm looking for a way of double checking it.

[Bass VI]

Without a schematic a multimeter will tell you very little, you may be able to measure 9 volts,etc. here or there but you won't know if you should have voltage there. Check your solder joints, 9 times in 10 when I have a problem like this, it's a bad solder joint or worse, I've soldered something to the wrong spot. Look carefully at the existing wiring in the guitar, did you knock a wire loose there, I know that sounds obvious but it happens. The down-side is even if you can check it, if it is fried, there's probably nothing you can do about it, most preamps ( onboard ) can't really be fixed at the circut board level. Check the connections, I'll bet that's it, also check the solder traces on  the circut board, sometimes they "peel up" if they get too much heat. You can use the meter to check continuity and power, but if it was working when you removed it and you didn't crack the circut board taking it out, I'm still thinking connection.

Good Luck,

Scott ( BassVI )

[drbassman]

Glad you answered this one Scott.  I'm clueless about electronics!

[Dave W]

[PhilT]

Thanks Scott. I'm paying the price for a bout of dreadful indecision. I started out with a Spector Rebop - liked the bass but not the tone, so changed the stock preamp for the Aguilar. Still didn't really get on with it, so I thought, put the original preamp back and sell Rebop and Aguilar separately. But, having - I thought - carefully documented the original wiring before removing the preamp, I couldn't get it to work. So I put the Aguilar back and that didn't work either. Then I wired it up passive and found the EMG HZs sound pretty good that way. So I may well end up keeping the Rebop passive, which is probably heresy for Spector fans, and I have this preamp which may or may not still work, and I really hoped there was a way of checking its health without reinstalling it (again!).

It probably was my soldering - I wasn't in a very good mood to be doing that sort of thing, and it was really too late at night.

Thanks for the sympathy, Dave. Actually I agree with your sentiments 110%. No more active basses for me.

[Dave W]

I'll admit to having two basses with active preamps. Just couldn't resist poking a little fun.

[drbassman]

I've only had one active bass (Fender Jag) and it sounded great to be honest, but I always worried about the battery crapping out.

[Bass VI]

All,
I'll admit to owning a few active basses ( including two Ovation Magnums 18v Yikes!!! ) and they do have some dubious advantages, but as of the last five or six years, they spend most if not all of their time in the case or on the wall as "art". Hmmm, five or six years......that's probably about the time I started repairing other peoples basses for a living....coincedence? I think not!  Seriously Phil, if you suspect your wiring/soldering that's probably it, I do it ( although not as often as I used too ) and it can be really frustrating, I've chased bad grounds and tiny wires that didn't look broken ( but were ) until I wanted to throw the thing across the parking lot. Usually a little "time out" helps  . In regard to checking your pre without reinstalling it, you should be able to wire up the "ins" and "outs", solder a couple of leads where the pickups would go and wire a 1/4" jack to the output, hook it up to an amp ( don't forget the battery ) and touch the "pickup" wires together, you should get a pop or hum or something to indicate signal. If you want to get tricky, adjust the tone controls and see if that changes the "tone" of the hum. That should let you know that it's at the least passing signal.
Once again, Hope that helps and Good Luck,

Scott ( BassVI )