my subwoofer is going nuts!!!

[flippyflipz]

hey guys i need some help. i have a jbl pb10 subwoofer and its great. however, recently when the system is turned off the subwoofer will just madly make a loud noise like a big rig is passing by or not work at all. other times it just works fine. anyone have any problems like this before??? and if there is anything i can do to fix it can i???

[timc]

hey guys i need some help. i have a jbl pb10 subwoofer and its great. however, recently when the system is turned off the subwoofer will just madly make a loud noise like a big rig is passing by or not work at all. other times it just works fine. anyone have any problems like this before??? and if there is anything i can do to fix it can i???

sounds like you might have a grounding issue. Check if all your cables and plugs are ok.



-tim

[boputnam]

sounds like you might have a grounding issue. Check if all your cables and plugs are ok.

Tim, I wondered that too, but the offered symptoms are not consistent with a GL.

I suspect there is an issue with the entire on-board amp.

Do some tests:

- disconnect the sub signal from the system, keeping the AC connected. Does the symptom still occur? I suspect the power amp or it's power supply are failing.

- is the sub on the same AC source as the system? If not, Tim may be right and you need to make it so. However, your description does not suggest this.

:dont-know

[Chas]

My 2 Cents worth: do everything the folks recommend above. If it is a powered sub, look out ! - There is a nasty cheap electrolytic capacitor that can fail prematurely at the output. Change it out now, if this is the case.

[Zilch]

Does the forum know something about PB series subs?

Search "PB12."

Is it the same amp module?

If so, figure out which Parts Express plate amp would be an appropriate retrofit and do it before the driver gets blown....

[Don C]

Service manual.
http://manuals.harman.com/JBL/HOM/Se.../PB10%20sm.pdf

[timc]

Tim, I wondered that too, but the offered symptoms are not consistent with a GL.

I suspect there is an issue with the entire on-board amp.

Do some tests:

- disconnect the sub signal from the system, keeping the AC connected. Does the symptom still occur? I suspect the power amp or it's power supply are failing.

- is the sub on the same AC source as the system? If not, Tim may be right and you need to make it so. However, your description does not suggest this.

:dont-know

I'm not thinking about a ground loop. I meant that this can occour on some amps if it looses the signal grounding.


-Tim

[johnaec]

Since it happens *after* the amp is turned off, it seems to me it points to a problem with the power supply caps circuit.

John