Audio problems with P A System

[isaachubbard]

I have a Gemsound BA-200 (It's a PA system that you plug microphones into with a 15" speaker, 3 tweeters and a mid)that was dropped and then started sounding "staticy", like a blown speaker sounds. I tested the 15" woofer alone and it sounds fine (pretty dang good, really). All connections look fine, no blown caps that I could see. Any ideas where to start looking or what to test next? Any help is much appreciated!

 

[cyclecamper]

Does the objectionable noise come from just one of the drivers, or all?

 

[isaachubbard]

It seems to come from all.

 

[AndrewT]

disconnect all but one driver. Keep the crossover intact.

Listen to each driver in turn.

Then add a second driver and listen again.

I suspect a loose/moved magnet that has changed the VC gap.

 

[wg_ski]

I suspect a loose/moved magnet that has changed the VC gap.

I would too - if the woofer didn't sound ok by itself. When that happens, it rubs and it's easy to diagnose by inspection. If the drivers test ok, I would suspect a cracked amplifier PCB. Where to start looking would depend on *how* staticy it sounds. If it's just a little staticky at low volume, the bias may be out of adjust. If it's VERY staticy it might have lost a rail or an output transistor (or connection to it).

 

[simon7000]

Check the microphone.

 

[pinkmouse]

And the mic lead.

 

[isaachubbard]

Thanks folks for the help. The speakers all sound fine when tested alone, and the PCB(s) look fine. I fired it up the other day, and after being powered on for about 1/2 an hour it started to sound fine. Bad caps, ya think?

 

[Brucester]

Newbie chiming in.

Sounds like a hairline crack exists somewhere on the board.
You might want to inspect the solder joints around and beneath the larger components on the board. Transformers and large caps are especially vulnerable to impact damage.

Sometimes a lucky shot of freeze spray will help narrow the search for the fracture(s) since it clears up when warm.

My $0.02