Simply replace them and don't wait to do so. My experience with QSC's tells me they are getting hot and are starting to build resistance. They may work now but will fail before long. Its not a difficult job and one that is much easier to do now.
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Tengo un qsc mx1500 pero el canal uno se queda flisado en rojos ambos , y el canal 2 funciona bien .!! Lo destape y la placa se ve como sobre calentada .! Solo quiero saber que es lo que más se daña
Please post an english translation, I used translate.google.com
Please post an english translation, I used translate.google.com
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I have a qsc mx1500 but channel one is split in red both, and channel 2 works well.!! Uncover it and the plate looks like it's overheated! I just want to know what is most damaged.
When I blow the image way up I can see a component lead and it’s shadow in that red circle. But the whole board looks like a number of solder joints could be suspicious. A lot of discoloration too - don’t know how much is due to heat and how much to contamination/moisture. The amount of corrosion on and near the fan itself is incredible. Was it installed right near running water?
In itself, I bought it from a friend who gave it to him and only one channel works perfectly. The fan doesn't work for you!! What will be the solution? Should I change the 2sb554 transistors?
If a 2SB554 fails there is usually a reason. They don’t go unless there is a sustained overload or something else goes taking them with it. You won’t see an isolated output transistor failure. With some of the other cheap types they’ve used over the years, maybe, but not with the best output tranny Toshiba ever made.
One thing to check immediately if you’ve had a transistor failure is the bias thermistor (R722 in the MX2000 here). They are mechanically very fragile and I’ve seen the leads corrode right off them three times now. One Model 41 and two USA1310’s. The symptom is the output stage running hotter than the blazes of hell and damnation. The 1310’s survived because of the 15024/5 outputs. The 15015’s they used in the earlier model didn’t fare so well and shorted out. You’ve got a lot of corrosion inside this thing and it wouldn’t surprise me if the bias circuit failed.
One thing to check immediately if you’ve had a transistor failure is the bias thermistor (R722 in the MX2000 here). They are mechanically very fragile and I’ve seen the leads corrode right off them three times now. One Model 41 and two USA1310’s. The symptom is the output stage running hotter than the blazes of hell and damnation. The 1310’s survived because of the 15024/5 outputs. The 15015’s they used in the earlier model didn’t fare so well and shorted out. You’ve got a lot of corrosion inside this thing and it wouldn’t surprise me if the bias circuit failed.
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Corrosion like this is caused when the amp is used in an atmosphere where smoke machines are being used frequently. The atomised fluid is sucked in by the fan and forms a hygroscopic layer that holds moisture and causes corrosion (usually around the fan the most). Also happens lot's on moving head lights etc. (anything else used around smoke machines too) ... I've also seen TV's in clubs and even some types of flooring damaged by prolonged exposure to atomised smoke fluid ... 😳
QSC MX's and Series 3 are workhorses amplifier. Just replace those bulging caps and check bias and they will last you another 30 years. I serviced tons of them and they are very easy amp to work on because each amp module is removable and modular.