Hi I have a JBL PSW-D110 and it is humming loud. The fuse is not blown. It has always been connected to a surge protector power strip. The power LED lights up in green... I have some knowledge of electronics but I don't have the schematic for this unit. Besides if you could point me directly to the faulty components it would save me lots of time and frustration. Please help.
D. Mark Ellis
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I would say it's a case of bad filter capacitors in the power supply. Without the capacitors, the AC power line doesn't get smoothed out enough when converted to DC by the supply, and you hear the hum that gets through. I have never worked on on one of these so I can't tell you how to open the case to get at the supply. It's not always a simple job. But if you can get at those caps and check them, you'll probably find them at fault. It's not a difficult job to remove and replace bad capacitors if you are comfortable using a soldering iron. Just make sure that replacement parts have at least the same voltage voltage rating and capacitance values as the originals. It never hurts to go higher by a little, but not lower.
There is a standby indication that activates after 10-15 minutes without any input signal. I suspect that might be what the red light is telling you - no signal.
Loud hum from a loosened cable is normal as hum usually means there's an ungrounded connection somewhere acting as an antenna and the amp is doing its job to amplify what it thinks is a signal, in this case 60hz stray ac current is being sensed nearby. It's a good sign that you get hum from the sub because that means the amp is alive.
Avoid manipulating cable connections with the Sub or Receiver turned on as you could introduce a static spike that could harm any connected equipment.
Are you certain a bass signal is making it into the sub? The complexities of modern AV receivers vary in how you configure them to direct LFE to a sub. Bone up on that end of the chain.
Or, just hang a CD player on the Inputs of the sub and play something with a reassonable amount of Low Frequencies.
>>>> Be advised that this way of testing has NO VOLUME CONTROL because amps without volume controls always operate at maximum gain, relying on your external controls to attentuate it (hence, the loud hum from a loose cable); so choose a track that eases into the loud parts with some quiet parts up front and BE READY TO PAUSE THE PROGRAM AT ANY SIGNS OF STRESS. <<<<
A living sub will produce only muffled rumble in the absence of other speakers producing the higher frequencies which carry the intelligence of the signal. If that works, back to the receiver for settings. If not... sigh.
For hum problems, even those you cause yourself:
Disconnect all inputs to see if that helps. If it goes away start with the signal cables and add in things until it comes back.
Sometimes the reversing the orientation of the AC plug can help with hum. Or it could be something like a loose or high resistance connection internal to the sub. Good luck.