Jacked up Fender PA - clip

[006]

My friend has a Fender portable PA system and he brought it over to see if I could figure out what's wrong with it. I can't. But I recorded clips of what it is doing:



In the clip there are 5 segments, they are as follows:

• Both Speakers
• Left Speaker > Left Output
• Left Speaker > Right Output
• Right Speaker > Right Output
• Right Speaker > Left Output

The thumping noise will go non-stop the entire time the PA is turned on, never varying in tempo or sound. If you plug anything into the PA, such as a mic, no signal passes through, just the noise in the clip. Adjusting any of the knobs on the PA also does nothing to alter the sound.

So the observations I have made:

• left speaker has a "busted tweeter" kind of sound to it
• right speaker has a low frequency thump sound
• left speaker sounds the same ("busted tweeter," albeit quieter) plugged into right output
• right speaker generally sounds the same (low freq thump) from either output

I initially thought it could be related to the output section, power amp, etc. But because the speakers sound the same in either output, that makes me think they are the culprit. I've just never heard anything like it before so this is new to me.

Anyone know what it is? Easy to fix perhaps?

 

[006]

.

Sweet, thanks!

 

[SethTheGreat]

Check out the amp's circuit boards (probably the power supply since it's affecting both channels) for a bloated or oozing capacitor.

edit: Another reason to believe it's a bad power supply

http://ibsubwoofers.proboards.com/index.cgi?action=display&board=amps&thread=1903&page=1#26179

edit: And another

http://www.justanswer.com/home-theater-stereo/7l4tx-subwoofer-not-woofing-tries-system.html

 

[fade_2_black]

As SethTheGreat has said, it's 95% likely to be a blown capacitor somewhere in the power section. When you have something like that at a consistent tempo, it's most commonly a capacitor charging and releasing charge at a steady rate.

It sounds more like the left speaker has a blown mid while the right has the blown HF.

Either way, likely story is some sort of voltage spike into the power supply causing the capacitor to ping and also sending too much voltage to the speakers, causing some to blow.

 

[Sloan]

Have you isolated the problem to the preamp or poweramp stage?