power amp problems

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michaelq

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i have a audio choice qm4 power amp that won't power up at all...its been serviced in the past and as i now have a little more knowledge of electronics i'd like to try repairing it myself. what i was wondering is if anyone has any idea of where to begin to look if it wont power up at all, and what kind of tests (if any) i could run...i know this leaves it wide open for probably a number of possibilities...everything looks good inside upon visual inspection. the amp worked one day and wouldn't power up a day later and has just been sitting the last few months..so if anyone can even point me in the right direction (even if its a link or book, it'd be greatly appreciated)...thanks -michael q
 
Michael,

No problem--piece of cake:)
Something tells me that it is something simple--bad switch, loose contact, etc. I assume you have already checked fuses...
You will need a tester, wich can measure AC and DC voltage. The very first thing is to check if main voltage reaches primary of power transformer (measure AC). If yes, then measure voltage on secondaries.
If no, then check the voltage before and after power switch to rule it out. Then report results and we will see what to do.
 
okay marik...initially i was told fuses had been checked, but i checked them now and that was the only problem...quite a simple fix..but now i have another item that won't power up..its a behringer ub1204fx pro mixer...just stopped working mid-use..i changed the fuse right away but that wasn't the problem. i opened it up and its seemingly far more complex inside..i dont know if i'll even be able to tackle this myself without taking it in, but would you advise the same...buying a tester for ac/dc voltage..i'll post this elsewhere as well but if anyone has any recommendations for an ac/dc voltage tester thats reasonably inexpensive and works well for these sort of applications say so. -michael
 
Michael,

I am a wrong person to ask about testers, as I have always used Fluke and only Fluke (you could get a new mixer plus a couple SP B1 for its price). I would think any DMM would be just fine as long it does its job measuring and you don't need high precision. I am sure your mixer has something simple, as well. Check all the contacts, first. Some of them might be covered with shrinkable tubes. If it doesn't help, the procedure is the same as outlined above.
 
I just got an Audio Choice QM 4 powered mixer and I get sound for music but no sound when I hook up a mic? Can anyone help me with this?
 
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