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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
sailcappy OP
57 posts
 
I will try to plug the unit into another outlet in the building. Belive it or not in the hall the outlets are twisted types so I can not use them. I am also looking into purchasing the Purepower 2000 which is an AC regenerator to try to solve my problem. If that works I will sell my SR Powercell.

No word on the O scope from Ken as of yet. The saga continues.
atmasphere's avatar
atmasphere
11,783 posts
 
Sailcappy, has anyone recommended installing a current inrush limiter? This is a device (goes inside the amplifier) that when cold has a high resistance and as it heats up, goes to a low resistance. They come in different current ratings; for example in our MA-1 we use CL-30s, two of them, which limit inrush current in the two AC circuits in the amp. They prevent the power switches from being damaged, and there are MA-1s out there made back in 1987 that still have good power switches, so these things work.

In your case they would give the power supplies a little more time to charge and obviously could keep the inrush current to an acceptable level. I think this would work much better than a long power cord, and if there are no inrush limiters in the unit, there totally should be...
sailcappy OP
57 posts
 
I have a PurePower 2000 Regenerator arriving at my home on Monday. Will install it on Tuesday and report.
sailcappy OP
57 posts
 
Well that did it. The PurePower 2000 regenerator fixed the problem. I no longer need the 50' extension cord. I am guessing it was harmonics since the PP2000 creates a new AC current that is clean. Still not sure what was wrong and i guess unless I want to pay an electrician (which i do not) I will never know. I have a solution and that is all i care about right now.

Thanks to all for you help and assistance.
atmasphere's avatar
atmasphere
11,783 posts
 
If it was harmonics, no electrician can help you. The power company can though.

Its the 5th harmonic (300Hz) that causes most of the troubles and it can cause transformer cores to become noisy. Not heard of it actually causing an amplifier to shut down, if so the problem is profound and the power company should consider upgrading the local transformer that feeds the building.
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