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Amp Shutting Down, need help

I have a Cary 7.250 brand new amp that shuts down after 20 seconds in my NYC apartment. I have sent the unit back to Cary where it tests fine. I have tried the unit at my friend’s apartment and his place of work and it works fine. The unit is 100% in working order. After talking to many people I was told to attach a 50' extension cord and low and behold it worked.

The good news is that I have a dedicated 20amp circuit to this outlet. My voltage reads 118 volts and Cary said that is not a problem as the unit will work between 90 and 130 volts. I have tested for voltage on the negative lead to ground and there is no stray voltage. I have also tried the unit on other outlets in the apartment and the same problem occurs.

My mono blocks and all other components work just fine. So I’d love to hear suggestions as to how to get rid of this 50’ extension cord?

Thanks in advance.
sailcappy
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almarg
9,670 posts
 
Sailcappy, Ralph is referring to seeing if the problem occurs when the input connectors of the amp have shorting plugs, such as these, on them.

If you don't have any, you could pick up some RCA plugs at Radio Shack and solder their center pin and the ground sleeve connections together.

Alternatively, you could connect RCA cables to the amp, leaving their other ends unconnected, and WHILE THE AMP IS TURNED OFF stuff some aluminum foil into the unconnected ends of the cables to short the RCA center pin and ground sleeve together. You would want to make sure that the foil is securely in place, so that it won't dislodge when you turn the amp on, and to be careful to not let anything or anyone touch the RCA plugs while the amp is on (and for a minute or more after it is turned off).

I'm not sure what possibility Ralph is envisioning in suggesting that experiment, though. Perhaps that the current surge that occurs at the 20 second point is causing a transient to couple to the inputs of the amp, and to then be amplified to excessive levels, somehow resulting in the breaker tripping.

Regards,
-- Al
sailcappy OP
57 posts
 
Should I put shorting RCA's on all seven of the inputs? What do i do with the XLR's?

Sailcappy
sailcappy OP
57 posts
 
Installed the Brick Wall today and it did not solve the problem.

I guess Ken and his Oscilloscope is the only solution.
jea48
4,425 posts
 
I guess Ken and his Oscilloscope is the only solution.
09-03-12: Sailcappy
Not the solution but maybe find the problem.

Sailcappy,

While you are waiting for ken....

It was suggested to me, by an AA member, to try the amp in another apartment in your high rise building.

He also suggested you check the common house corridor on your floor, outside your apartment, for a receptacle you could plug the amp into. There is a very good likelihood the receptacle, in the corridor, is fed from a different distribution power transformer than your apartment electrical panel.
gbart
290 posts
 
If it were me, by now I would be either trying to get my money back or llooking to sell the amp. Before owning my own house, I lived in an apartment with a single 15A circuit serving the entire place. It does not get worse case than that. I owned several high powered amps during that period and never once experienced a shutdown problem. Cary gave the amp a clean bill of health, therefore it should not be having the issue. The amp seems like more trouble than it's worth, IMHO.
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