Amp Shutting Down, need help

The 15amp circuit breaker (which is the on off switch for the amp) blows after 20seconds.

Now that is a horse of a different colour!

Primary winding inrush current draw of the power transformer/charging electrolytic power supply caps is causing the circuit breaker on the amp to trip open......

The 50' cord is working like a soft start circuit limiting the inrush current draw to the Cary amp. At least that is what it sounds like to me.

What can you tell me about the 120V 20 amp dedicated branch circuit.
Distance from the electrical panel?
Wire size?
Electrical panel manufacture?

Another test....

Multimeter set to AC volts.
Insert the test probe leads into the unused receptacle of the duplex receptacle. Make note of the voltage reading. Cary plugged into the other recept.

While watching the meter flip the switch on the Cary to the on position. Note the reading/s of the meter.

Does the voltage sag several volts and remain low until the amp's breaker trips open? Voltage reading/s?

OR

Does the voltage sag and then swing higher than the original no load voltage? Voltage reading/s?
.

Well, I'm out of ideas without being there - armed with test equipment. The fact that it works at Cary, and your friend's location(s), without the addition of extra impedance (wire length), clearly indicates some thing's up with your apartment wiring, or induced noise.

08-14-12: Sailcappy
"He also noted that none of my outlets in my apartment are wired to ground it seems the ground is left to the junction boxes alone."

By that, I assume your outlets and junction boxes are grounded via metal conduit per local code? I'd have a warmer fuzzy if I knew the LINE/NEUTRAL voltage or resistance, and would still contact Cary to enquire about any grounding sensitivity issues with their circuits. As far as the level of noise it would take to cause your situation, is most intriguing.

The fact that numerous people suggested adding a 50' extension cord is interesting as well.

Besides Jea48, maybe member "Almarg" could offer some suggestions.

If you do get it resolved, be sure to post your findings.

Good luck

Jea48 - I can not thank you enough for your help.

1. No markings on breaker box at all. Building built in the 1970's
2. Outlet is about 40' from breaker box.
3. I was incorrect, there are 4 outlets on the branch but nothing is plugged into them.
4. The White and Black wires connected to the circuit breaker seem to be 10 guage.
5. I plugged the volt meter into the unused receptical next to the one the Cary was pluged into. With nothing else going on the voltage goes from 117.9 to 118.1. When I switched the Cary on the voltage did not change. Nor did it change during the 20 seconds it takes for the 15amp Cary breaker to trip. However when the breaker did trip for a split second the votage meter read 112 volts. I was able to re-create the same readings after 4 tries.

This is my friends theory. He works for the local power company. Let me know your thoughts.

"The breaker is a thermo-magnetic breaker and I think when the amp relays click off after it is done charging the caps, the break in load (which is not a smooth wave either) is sending a fluctuation back out on the incoming power that is causing the breaker to think there is an over current and trip. You should talk with Cary, but the solution may be to use a thermal breaker rather than one that is operated magnetically. The fact that the extension cord solves the problem supports this theory. The extension cord acts like a filter so when the amp relays open, it resists any power fluctuations on the line and therefore limits the magnetic field created on the breaker tripping mechanism."

I just want to listen to music :)

Hmmm, as you stated, it acts the same way from your 15 amp circuit as well as your dedicated 20 amp, yet works fine at Cary and your friends location(s) without the extension cord - when considering your friend's theory.

Jea48: As you know, "inrush" current is typically instantanious - with PS filter caps charged to 95+% within a few seconds, or so, for most high-power amps. Note he's stating the breaker consistantly trips "after 20 seconds", and even from several of his apartment's pre-wired standard 15 amp outlets. His recent noted voltage drop to 112, only at the moment of trip, is curious. For a thermo-magnetic breaker, you'd expect to see sustained high current voltage drop right up until tripping vs the virtually unaffected static 118 - as if the power supply wasn't even pulling current (?).

I just took a look at Cary's online PDF Owners Manual for anything of interest and there's not much to assist.

http://www.caryaudio.com/pdfs/manuals_2012/Model7.250_manual.pdf

4. The White and Black wires connected to the circuit breaker seem to be 10 guage.

Is the breaker a GFCI (Ground Fault Circuit Interrupter) or an AFCI (Arc Fault Circuit Interrupter)? These type of breakers have a test trip push button on them.

When I switched the Cary on the voltage did not change. Nor did it change during the 20 seconds it takes for the 15amp Cary breaker to trip.

Well that is good for the integrity of the branch circuit wiring. That tells me with the load connected the branch circuit maintained the supply voltage with little or no VD, (voltage drop) through the high inrush current cycle.

That also tells me the branch circuit is capable of delivering the inrush current draw of the primary winding of the power transformer.

However when the breaker did trip for a split second the votage meter read 112 volts.

I have a feeling the VD drop happened before the trip.....
Question is what is it and why?

At this point it would be good to hear from Almarg or Ralpf of Atma-Sphere Music Systems.

As for your friends theory he could be onto something.

By chance does your friend have a clamp on amprobe so you could measure the inrush current draw of the amp on startup?

As for the circuit breaker used on the Cary.... Is the switch actually a breaker? The handle trips position and has to be reset? If it is indeed a breaker the more times it is tripped the weaker it becomes.

Just can't beat a fuse for overcurrent protection for audio equipment.....
Jim