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Carvin B50 Active Electronics issue

bound'n'blocked

bound'n'blocked

Jan 25, 2010
2,939
4,911
Grayson, KY
#1
I just finished a Carvin B50 kit with the active electronics. Just to note, this was my first attempt at soldering ANYTHING.

Here is the problem. The bass works fine in passive mode. Volume knobs work as they should, passive tone knob works fine. Put the knob down to go into active mode and nothing. The batteries are brand new. I pulled up the little tabs in the battery compartments. All the solder joints look fine.

I wouldnt think the preamp is dead to start out. Sounds like it would be something related to power since the passive option works ok.

Any ideas?

BnB
 
#3
Roy Vogt said:
I'd check the battery connections onto the circuit card.
Click to expand...

+1. also check you didn't accidentally ground something to the shielding tape in the cavity, loose wire or one of the contacts from the pots. If you plug it in at a low volume and remove things one at a time chances are you'll find it. But like Roy said check your battery and all your wires one by one first.

Good luck!
 
#5
Roy--
I think the connections to the board from the battery compartments are good. I did re solder one of the wires but no change.

aproud1--
I don't think anything but the two ground wires are soldered to the shielding tape (one from the bridge and one from the jack.)

Toptube--
No worky with cover on or off.

I took it to rehearsal tonight and noticed I had to tap the end of the cord in the jack to get it to work in passive mode.could it be something in the jack not making a connection?

I can't imagine how good it must sound active...it's brutal sounding passive.

BnB
 
#7
Look for wires or parts touching the shield tape. You may not have soldered them there but trust me it happens. If part of a pot or your jack unintentionally touches a ground point(like your shield) all of your signal will go there. your shielding tape could barely be touching something it shouldn't and shorting your electronics to ground.

I only know because it has happened to me... many... too many times.
 
#9
Leave everything wired properly but make sure none of your connections are touching the shielding tape unless it's supposed to. Chances are your jack or the 1/4" plug when it's in your jack or the solder points of one of your pots is touching ground.

Let us know what you figure out and again good luck.
 
#10
UPDATE:
I had a show Friday night, and even with the issues with the bass I wanted to use it anyway. The sound guys are all good friends and we were just hanging out during the day. I took my bass up and plugged in and got a horrible buzz. I tried my head, their head, with my sansamp, without it, switched out every cable, lifted the ground and still had the buzz, which I hadnt had befor with the bass. So I finally tore into the bass and made sure nothing was touching the shielding tape in there. I took the ground from the bridge that was soldered to the shield (as someone had told me to do) and the ground wire from the jack(also soldered to the shield) and tied them together. NO HUM!

But, now I still have the no active problem, and I have to twist the cord end in the jack to get it to make contact and then make any sound. I think the active problem might be in the jack, or the preamp is screwed in some way.

BnB
 
#11
Not sure if you know this but...if you line the cavity with copper tape, you should solder the copper tape everywhere they meet with another copper tape. This will tie them "electrically" together. Just laying the copper tape over or next eachother, will not make it conductive to eachother. So in your case, the jack ground and the bridge ground (although both being soldered to copper tape) had no continuity with eachother...if that makes sense.

Can we get a photo of your cavity with the preamp in it? Lately, Carvin has been using a "fancy" stereo output jack that I had problems with on one of my basses. I replaced mine with a Switchcraft jack and been trouble free since. To be fair, I have 2 other Carvins with this "fancy" jack that's been working fine.
 
#13
Funkinthetrunk said:
Lately, Carvin has been using a "fancy" stereo output jack that I had problems with on one of my basses. I replaced mine with a Switchcraft jack and been trouble free since. To be fair, I have 2 other Carvins with this "fancy" jack that's been working fine.
Click to expand...

Good call...

I finally got the chance to drop it off at a local shop. Repair guy replaced the jack and now it works great! He made the comment that that was the poorest jack he had seen. Places where it should have made contact weren't. I left my other bass that is also having issues with the pre and told him to check the jack first!

Thanks for the help with this guys....I love how helpful people are on this site!

:bassist:

BnB
 
#14
bound'n'blocked said:
Good call...

I finally got the chance to drop it off at a local shop. Repair guy replaced the jack and now it works great! He made the comment that that was the poorest jack he had seen. Places where it should have made contact weren't. I left my other bass that is also having issues with the pre and told him to check the jack first!

Thanks for the help with this guys....I love how helpful people are on this site!

:bassist:

BnB
Click to expand...

Cool...I was wonderin' what became of this issue...
 
#15
bound'n'blocked said:
Good call...

I finally got the chance to drop it off at a local shop. Repair guy replaced the jack and now it works great! He made the comment that that was the poorest jack he had seen. Places where it should have made contact weren't. I left my other bass that is also having issues with the pre and told him to check the jack first!
Click to expand...

Excellent. Amazing the difference a $3 part can make. Glad it's all sorted out.
 

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