[alan halvorson]

I've owned and used a Crown Macro Reference power amplifier (now call Studio Reference) for at least 10 years; maybe more, it's hard to remember. It has performed perfectly, except for a little turn-on pop, in all that time, but starting a few months ago, once every 5-8 times I turn it on, the amp trips a 20-amp circuit breaker. Big pain. After resetting the breaker, it turns on ok and performs perfectly after that. It's never had any turn-off problems.


I finally got sick of resetting the circuit breaker and brought the amp to a Crown authorized repair center. After replacing a capacitor and a couple other parts and turning it off and on 30-40 times without incident, the amp was declared to be normal. I get it home and for a few days it operates just fine, but then it trips the breaker again - not fixed!


So - back to the repair place I go, but the technician can find nothing wrong with the amp. Everything is within spec. He believes that because my system is plugged into the same circuit (because of hum problems) as the amp and because the amp has a heavy current draw on turn-on causes the circuit breaker to trip. I just don't see it. The amp has only been tripping breakers for a few months. While my equipment content changes once in a while, I've always had approximently the same number of components. None of the components other than the amp has a heavy current draw (no other amps). A similarly rated QSC SRA 3622 power amp that I had been using in place of the Crown (but just sold) had no turn-on problems on the same circuit.


The technician suggests that I may have a faulty breaker (the service is only a few years old). Or, if it's not faulty, that I install something called a "Motor Start Breaker". I have no idea what this is but I might try it. I still believe that something is wrong with the amp, but I'm not an electronic genius and can't suggest what it might be. All I know is that tripping circuit breakers ain't normal.


Anyone have any thoughts or suggestions?

 

[TonyBDA]

From all the symptoms, sounds like you have a faulty circuit breaker.

 

[gohd]

Agree w/ above. Had similar problem with my A/C unit in my house. Worked fine for months then suddenly started tripping the breaker every so often. Bought a new breaker (not the whole panel) and was ready to replace it, when I found the actual breaker was loose and not fully connected to the ground bus bar ("hot" one in the breaker panel; I think that's what it's called). Just pushed it back in and haven't had a problem since.


But, with electrical stuff, could be anything.

 

[MikeTz]

With motor based appliances like air conditioner compressors, refrigerators, and the like you get an inductive current spike for a very short period of time then a much lower "quiescent" current draw from the appliance. A powerful amp with a large capacitive bank and the absence of "soft start" circuitry may also produce an instantaneous current spike that can trip the breaker. The Motor Start Breaker is not as sensitive to the turn on spike and won't trip as quickly. That's what the Tech was suggesting.


The real question is what's going on with your circuit. If you have several components plugged in to the same line the steady state current of all the devices may be within the current capacity of your breaker but simultaneously turning on multiple devices may cause a short duration current spike that trips the breaker. Since you indicate the problem is intermittent there are a few things you can try. With nothing else on can you make the breaker trip by turning on the amp alone? If you plug the amp into another circuit can you trip the new breaker?


If the amp alone trips the existing breaker but not the second breaker than Tony may be right and you might want to replace that breaker. If the amp doesn't trip the existing breaker then you might consider putting your other components on another circuit. If the amp trips both breakers then keep looking at that amp (especially the capacitor bank and associated components).


Good Luck


MT

 

[TonyBDA]

When a motor starts from a rest position, it draws a maximum amount of current. Effectively the motor is in a locked rotor condition and present a short circuit to the source. Once the motor begins spinning, the back EMF reduced the current flowing through the motor.

Motor start breakers allow for the surge.


When a large amplifier, or other electronics, are powered on, the power supply caps, if completely discharged, will present a breif short circuit to the supply. As the caps charge this current decreases.

On older equipment, the capacitors lose their capacitance as the electrolyte dries out, thus presenting less of a surge load at power on.

Since your amp is old, I don't suspect the fault is with the amp at all.

 

[thebland]

Quote:

Originally Posted by alan halvorson A similarly rated QSC SRA 3622 power amp that I had been using in place of the Crown (but just sold) had no turn-on problems on the same circuit.

The QSC amps ( I own 4 of them) are digital amps and when switched on the draw is almost zero and then it gradually, but quickly, ramps up. This is very easy on you breaker. Your Crown unfortunately draws big current on power up (I own 2 K2 amps) and may the straw breaking your breaker's back.


What is your electrical situation? If it is not dedicated, you may need to add a dedicated circuit.

 

[Bob Lee (QSC)]

Quote:

Originally Posted by thebland The QSC amps ( I own 4 of them) are digital amps and when switched on the draw is almost zero and then it gradually, but quickly, ramps up. This is very easy on you breaker. Your Crown unfortunately draws big current on power up (I own 2 K2 amps) and may the straw breaking your breaker's back. What is your electrical situation? If it is not dedicated, you may need to add a dedicated circuit.

QSC has never made any digital amps. Maybe sometime in the distant future, but not to date.

 

[thebland]

OOOPS.....didn't mean to say digital. Gotta quit that coffee.

 

[TonyBDA]

Quote:

Gotta quit that coffee

too alert?


Are there any digital amps the 'ramp up' power? How?...or is this a 'wish' as opposed to fact?

 

[alan halvorson]

All right - thanks for the replys. Something to try and look at when I get my amp back later this week. Wished I hadn't sold the QSC, but I needed some cash and the QSC is worth more than the Crown and I couldn't see having one amp lying around (I don't have a surround system).