Amp Shutting Down, need help

Hi Ralph,

I learned a couple of weeks ago from Jon Risch, an EE as you know, that a SMPS will draw more current if the voltage sags to try and maintain output power of the PS.

Sailcappy has verified the mains voltage at the dedicated branch circuit receptacle is 118V using a true RMS meter. That is only one volt above what the manufacture recommends for the amp.

In Sailcappy's test he ran for me, with out the 50' 16/3 cord connected to the amp, amp plugged directly into the wall recept, the mains voltage dropped from 118V to 112V at the same instance the 15 amp magnetic breaker tripped open.

With the amp connected to the 50' 16/3 cord the voltage at the end of the cord was 118V unloaded, naturally, and at the sound heard from the last relay closing the voltage dropped from 118V to 115V then back to 118V as the amp
completed its start up cycle.

So is the 50' cord working more like a current limiter
keeping the current below the 15 amp cutoff of the magnetic breaker trip solenoid mechanism?

It would be interesting if Sailcappy were to plug in a 120V table lamp with a 60 watt incandescent light bulb into one of the recepts of the branch circuit that feeds the Cary amp, then start the amp up, plugged directly into the wall recept. I wonder how dim the light gets at the split second before the magnetic breaker trips open?

A lot? Somewhat?
.
Jim

Sailcappy has verified the mains voltage at the dedicated branch circuit receptacle is 118V using a true RMS meter. That is only one volt above what the manufacture recommends for the amp.
09-10-12: Jea48

That is only one volt above what the manufacture recommends for the amp.

Should say,
That is only one volt above the minimum line voltage the manufacture recommends.
From the Cary 7.250 specs, (AC Power Requirements 117/234 Volts AC @ 50/60 Hz)

Also after rereading my last long winded post I am not sure I made clear what I was trying to get at.....

That a SMPS will draw more current if the line voltage sags to try and maintain output power of the PS.

So, Is it possible the voltage drop from 118V to 112V is enough to cause the SMPS to draw more current to compensate for the drop in line voltage?
End result the 15 amp magnetic breaker ampere rating is exceeded, breaker trips open.
.

Jim -- I don't see the 117V being indicated as a minimum. I would assume it is intended as a nominal value.

Best regards,
-- Al

Jim -- I don't see the 117V being indicated as a minimum. I would assume it is intended as a nominal value.
09-11-12: Almarg

Hi Al,

Ya, I agree. I knew better... I'll just have to blame the thought on a brain fart moment.

120V may be the nominal voltage in the US but it is not unusual to see line voltage vary anywhere from 110 to 124.
.
Jim

Switch mode supply??! I figured this thing had a big toroid...

Clearly the current limiting of the cord is having an effect.

So what is the outlet voltage while the amp and the cord are doing their thing? Bet it does not drop as much.

Based on that I would replace the AC receptacle, and make sure the screws on the receptacle are tight!

It would be a really good idea to see how this amp behaves in another apartment in the same building...

I do not think the amp is at fault if it really is SMPS powered.