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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
atmasphere's avatar
atmasphere
11,807 posts
 
If it has large toroids, there is no SMPS. A SWPS might look like an aluminum box inside the unit, but certainly would not sport any toroids, especially large ones.

So the theories around SMPS are not.

I still think its a good idea to try this amp in another place in the same building. Also, it would be a good idea to get the AC voltage readings from the wall when the amp is plugged directly into the wall, and also what the outlet voltage is when the amp energizes at the other end of the power cord. I'm thinking this might have to do with current inrush caused by an excessive dip in the line voltage at turn on, due to saturation in the core of the transformer caused by the dip itself when the transformer energizes.

If that is the case, it may be that replacing the outlet could sort it out....
jea48
4,425 posts
 
If it has large toroids, there is no SMPS. A SWPS might look like an aluminum box inside the unit, but certainly would not sport any toroids, especially large ones.
09-13-12: Atmasphere

Ralph,

Thanks for the response. My limited understanding of SMPS was that a power transformer was not used. Then I got into a discussion with Jon Risch which I apparently got confused thinking SMPS could also be used with power a transformer.

I obviously misunderstood what Jon was trying to tell me.
My bad.... Thanks for setting me straight.

http://www.audioasylum.com/audio/tweaks/messages/18/184672.html

http://www.audioasylum.com/audio/tweaks/messages/18/184672.html

.
Jim
jea48
4,425 posts
 
Correction.
Should read,

Then I got into a discussion with Jon Risch which I apparently got confused thinking SMPS could also be used with a power transformer.

Anybody ever wonder why the hell the user cannot edit a post after xxxx amount of posts have been posted?
.
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
11,807 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...
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