all hum, no sound from bridge PU

[snowdan]

well my neuser courage is ill apparently.

she suffers from bad hum on the bridge pickup. the neck PU is free from any noise and working fine. the blend control works, but it blends from neck sound to hum only. solder joints to the humming PU seem to be OK. no loose joints in control cavity either, at first glance. the rest of the active electronics are working as usual.


what could be broken? the pot? the PU?

she needs help!
thanks in advance!

[pkr2]

Originally Posted by snowdan

well my neuser courage is ill apparently.

she suffers from bad hum on the bridge pickup. the neck PU is free from any noise and working fine. the blend control works, but it blends from neck sound to hum only. solder joints to the humming PU seem to be OK. no loose joints in control cavity either, at first glance. the rest of the active electronics are working as usual.


what could be broken? the pot? the PU?

she needs help!
thanks in advance!

I'm assuming that the bass is passive.

Does the hum respond to the volume control?

You can bypass everything in the tone/volume circuit for testing by temporarily connecting the pup output wire to the output jack. If still no volume chances are very strong that the pup has gone bad. Check for continuity between the ground and hot wire from the pup with the hot wire disconnected. Should read 4 to 8 Kohms, depending on the pup.

[snowdan]

it has neuser PUs and EBS active electronics.

any input on how to locate the problem is appreciated.

[pkr2]

Originally Posted by snowdan

it has neuser PUs and EBS active electronics.

any input on how to locate the problem is appreciated.

The fact that it's active opens up a can of worms, so to say.
The pups can be checked for continuity with an ohm meter but the preamp section is far beyond any diy repairs other than a close visual inspection for obvious probs such as broken wires etc.

You may be able to isolate the prob by just injecting hum at various points in the circuit by holding a small screwdriver by the meatal shaft and simply touching the tip to the hot wire that comes from the pup. If you get a pretty loud hum through the amp, chances are that the preamp is OK. The induced hum should be controllable with the volume control.

Unless you are fairly well versed in electronics, you probably will be better off taking it to a good electronics tech.

Afraid that I can't be any more help than what I've suggested, but good luck with it.

[Zebra]

Originally Posted by pkr2

The fact that it's active opens up a can of worms, so to say.

Really? I don't know my electronics all that well, but it would seem to me that the problem has nothing to do with the preamp. I would assume that the preamp is after the pickup volumes/blending pots in the chain. That said, it seems the problem clearly affects only one pickup, and that would suggest the problem is before the preamp. What kind of technical problem in a preamp would only affect one pickup in a two-pickup bass?

[snowdan]

then it seems it is either the pot or the PU, huh?

is there any good way to determine the functionality of the bridge PU?

[pkr2]

Originally Posted by Zebra

Really? I don't know my electronics all that well, but it would seem to me that the problem has nothing to do with the preamp. I would assume that the preamp is after the pickup volumes/blending pots in the chain. That said, it seems the problem clearly affects only one pickup, and that would suggest the problem is before the preamp. What kind of technical problem in a preamp would only affect one pickup in a two-pickup bass?

Sounds reasonable to me. A quick check with an ohm meter of the pup would seem to be the first check. The pup probably has an open coil.