Noisy Europa 5 with loose wire

[rickstevenson]

Just tossing this out there… how is your instrument cable?   I have a 3’ Monster cable that I use when I hunker down in the basement.  Recently it exhibits nasty noises if it is turned in certain directions (no more dancing and playing until I get a new cord).

Thanks.  I did try a couple of different cables but the noise was the same.  I also tried a couple of different amps just in case it was a weird interaction.

[rickstevenson]

Well, it's not actually fixed.  What's happening now is that every time the bass is plugged in, it makes intermittent bursts of the same sort of noises (hiss, crackle, wind in the trees) for a few minutes and then it (mostly?) stops.  If I unplug it for a brief period and plug it back in again it does the same thing again.


Another thing I have noticed is that the sound effects are affected by most of the controls - volume turns the noise up and down, the filter pot and tone switches vary the tone of the noise.  Pan makes no difference.


I'll be away from the bass for the next couple of weeks but any helpful suggestions would be appreciated!


Thanks,
Rick.

[JimmyJ]

Sorry to hear it's still acting up.  The fact that all the controls seem to be working correctly despite the noise points to the final stages of the circuit.  But I'm not familiar enough with this preamp circuit to know what that means. 

The next thing I would probably do is plug the bass in with the back panel off and poke around in there with a plastic or wooden piece (just not metal) to see if I could find a spot which makes the noise happen.  Check closely around that pair of switches (under your mystery wire) which have so many components hanging off of them to be sure no un-insulated wires are coming into contacting the switch cases or the shielding paint.  (Doubtful because Alembic takes all this into consideration). Also be sure the metal cylinder "choke" is not moving around and able to contact the switch or any other components.

Also, obviously, the 1/4" jack has got to be working solidly so if moving the plug around creates the noise then it might simply be corroded jack contacts.

I think we're getting closer.     Let us know what you find when you get back to experimenting.

Jimmy J

[rickstevenson]

Thanks, JimmyJ.  Will have a poke around when I get home in a couple of weeks.

[keith_h]

I'm a bit late but my thought is the loose wire was placed between the back plate and body in an attempt to ground the back plate. This should not be needed as teh back plate and cavity are coated with conductive paint and grounded through the component mountings.

The way you describe the noise I suspect a component problem as if it was an intermittent connection or poor solder joint I would not expect the noise to go away after being plugged in for awhile and not come back. In the mean time if you haven't already done it I would reseat all of the connectors and look for bad solder joints. I would also get some Caigs Deoxit and spray the 1/4 inch connector contacts while exercising them. Just be careful and protect the finish from overspray.

If push comes to shove you can always send the electronics to Alembic for testing. If they find something wrong they can give you an estimate of the repair cost.

[JimmyJ]

Good ideas from Keith. 

Yes the bare wire was probably just that, an attempt to ground everything which is already grounded...

Also a good idea to reseat the connectors.  Each one has a small latch locking it in place.  (See the pic).  Not much force is needed to release it but that's how they work.  And they'll snap back in place when you reconnect them. 

I would be surprised if you found any poor solder joints!  But I am voting for an issue with the 1/4" jack. Note that the mystery wire was hastily soldered to the ground lug of that jack which means it could have been overheated and messed with the contact tolerances...  Not to mention possible in-the-closet-age-related corrosion.  Wiggle that plug and see if that doesn't make a racket.

Let us know when you get back and have time to experiment.

Jimmy J

[mica]

In the next couple of weeks I'm hoping the new Europa circuit with an even better RF filtering will be available. This is something that Ron and Tom have been working on. It does sound like a capacitor failure and those Switchcraft barrel jacks, while the best available, only reliably work for 5-10 years. That's why it's supplied with a modular connector and the spares are sold in pairs, because if you're replacing one, it's best to have a spare in reserve.

[rickstevenson]

Thanks, keith_h, JimmyJ & mica.

I did reseat the connectors and have tried wiggling the 1/4" jack (it doesn't make any noise.) I haven't pulled out the preamp board and had a close look at it yet but I'll do that when I get back home.  Maybe there's a swollen electrolytic cap I can't see from above.


I also have some Deoxit so I'll clean all the contacts.

Cheers,
Rick.

[mica]

All the modular connectors are gold plated. The pots are sealed and the switches are epoxy sealed. There's not much for contact cleaner to do in there - it won't hurt anything, but it's not likely to help much either.

[rickstevenson]

All the modular connectors are gold plated. The pots are sealed and the switches are epoxy sealed. There's not much for contact cleaner to do in there - it won't hurt anything, but it's not likely to help much either.

OK, thanks.