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
Hi Jim,

Yes, I did look at the manual. As you realize, though, it does not appear to provide enough information for us to infer answers to the questions in my previous post.
If the unit is in active mode and power is removed, it will remain activated when power is restored.
Yes, I noticed that both in the manual and in one of your earlier posts. But what I'm mainly looking to establish at this point is what the amp's normal turn-on behavior is, in the situation where the breaker had been turned off only after standby mode had been entered.

Which relates to your point about inrush current. It is not clear to me when the major inrush current normally occurs. Does it occur:

(a)When the breaker is turned on, assuming that the amp had been left in standby mode when it was previously turned off. Or,

(b)Does it occur when the amp is switched from standby to active? Or,

(c)Does it occur 20 seconds later?

A related thought that occurs to me is that I would not assume that the voltage drop that was observed as the breaker was tripping was due to inrush current that normally occurs at that point. It seems conceivable to me that contact bounce occurring in the breaker as it tripped might have resulted in inrush current and voltage drop that would not occur at that time ordinarily. So the voltage drop might have just been a consequence of the breaker tripping, rather than reflecting a large inrush current that may have caused the breaker to trip. Or perhaps some sort of inductive kickback effect from the power transformer or a relay was responsible for the voltage drop, given especially that the amp was not designed with the expectation that it would normally be powered down from the active state by means of the breaker.

Just some thoughts.

Best regards,
-- Al
You know, as I read through all of this which is way over my head technically, I wonder, as I have from the beginning of this thread, why the OP uses the mag breaker as an on-off switch? And could that not be the major part of the problem? has the OP tried shutting down using the standby switch w the ext cord, and then leaving the breaker in the on position, plugging the power cord, sans extension, back in and again powering up from the standby switch? Perhaps he has and I missed it.
Hi Al,

4. Not sure what you are asking the 15amp breaker which is the on/off switch for the breaker trips it to the off position when I noticed this drop. Remember this happens after i go from standby mode to Active mode.
08-21-12: Sailcappy
From what Sailcappy says in the quote above the breaker trips as the amp moves from standby to active.

So question is what all is powered in standby?
Just the power transformer?
Or the transformer and DC power supply?

Which relates to your point about inrush current. It is not clear to me when the major inrush current normally occurs. Does it occur:

Good question.... And then there is the soft start feature of the amp?
Where is the circuit installed. Does it limit, smooth out the inrush on initial standby start up only? Or both standby start up as well as active mode activation?

A related thought that occurs to me is that I would not assume that the voltage drop that was observed as the breaker was tripping was due to inrush current that normally occurs at that point. It seems conceivable to me that contact bounce occurring in the breaker as it tripped might have resulted in inrush current and voltage drop that would not occur at that time ordinarily. So the voltage drop might have just been a consequence of the breaker tripping, rather than reflecting a large inrush current that may have caused the breaker to trip. Or perhaps some sort of inductive kickback effect from the power transformer or a relay was responsible for the voltage drop, given especially that the amp was not designed with the expectation that it would normally be powered down from the active state by means of the breaker.
Agree... As I said in an earlier post it could have just been a coincidence at the same time some other load started and the VD occurred at the main electrical panel.

How about that 50' 16/3 extension cord??
Yes the cord is too small for the amp.... But what about what is it doing?

Two things come to mind. If the current does go up as the amp goes into the active mode then I would imagine the voltage drops. Available Power at the end of the 50' cord would be reduced. Enough so the amp is able to complete the process of going into active and playing music without tripping the magnetic breaker.

You stated earlier you thought the amp might be reacting to voltage transients and thus causing the magnetic breaker to trip.

Would a good SPD, surge protection device, installed between the amp and the wall outlet shunt out the high voltage transients?

One last thought I wonder if it would help if the hot conductor of the 20 amp dedicated branch circuit was moved to the other line, leg, in the electrical panel?
Jim

Look! Every time I get close to addressing and finishing a few paragraphs in response, all you guys quickly sneak in answers and more questions! So, I'll just sit patiently in the corner with a "filthy bed-wetter" sign on and wait fer a bit. :-D

Now, how the hell are you guys (Jim & Al) quoting in small font?

Frank
Hi Swampwalker,

I believe when the amp is first powered up using the switch breaker on the rear panel of the amp the breaker holds in the standby mode.....

The proper shut down procedure is to first push the power button on the front panel of the amp. That puts the amp in standby. The user can then turn off the amp with the main power switch/breaker on the rear panel of the amp or leave it on 24/7.

From what I have gathered from reading Sailcappy's posts, the amp could be left in standby indefinitely and not trip the magnetic breaker.

The problem starts when he pushes the power button on the front panel of the amp that starts the sequence from standby to active mode.

The switch/breaker is in series with hot of the 120V power.
That makes the breaker the gate keeper so to speak......
Jim