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Old 14th October 2005, 12:33 AM   #1
pjpoes is offline pjpoes  United States
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Default Intermittent PA amp problem

I have a Sunn PA Mixer amp that I am trying to repair. I recieved a call from the owner asking if I could look at it, and before I open it up, I was wondering if, from the description, you could suggest some possible area's to look into.

The owner say's that the amp will just stop working. The Lights are on, everything appears to work, but no sound. It isn't constant. He says that he finds tapping on the microphone will eventually get the sound to come on. So will turning it on and off a few times. Any suggestions would be appreciated.
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Old 15th October 2005, 07:45 AM   #2
Enzo is offline Enzo  United States
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It would help to know the model since SUnn products have been around over several decades.

If this is one of the powered mixers in the shape of a guitar head - we call them "box mixers" - the first thing I would check would be the jacks along the lower right on the front. Connect a signal cord from MAIN OUT to POWER AMP IN. If this restores teh sound, then the power amp jack needs service. There are cutout contacts in teh jack that carry the signal past. if they oxidize or get dirty, then they DON'T carry that signal past.

Most mixers have several in and out jacks. COnnect the main out to another amp and see if the mixer is putting out any signal. Likewise, inject a signal into the power amp in jack to test the power amp. Of course we are assuming known good speakers and connectionms to the outputs.

By manipulating those various patching jacks, we can isolate the problem to part of the unit for further scrutiny.
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Old 15th October 2005, 10:36 PM   #3
pjpoes is offline pjpoes  United States
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Thankyou, that advice seems so obvious, yet I was ready to cut into the thing first. I hadn't thought of it, but I will do that next. I don't even know if the connections and speakers are good as I have not yet tested the unit myself. I witnessed the problem, but I was playing guitar at the time while he was playing with the unit, so I never had a chance to look at it. I dont recall the model anymore, it was fresh in my head when I wrote this, but now I cant recall. Its a box mixer type, like you said, and its of the newer generation, I believe from the 80's, maybe early 90's. My Father has owned it since about 94 or 95 I think.
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