Amp Shutting Down, need help

I don't think the ground is the problem.

Here is my theory:

Right now I think there might be DC on the line. DC can cause a toroidal transformer to saturate. Now what if its not very much DC, less maybe only about .3 to .5 volts...

In standby the amp might be OK. At full power the toroid saturates and the resulting inrush blows the breaker.

By adding the power cord there is enough voltage drop and resulting reduction in current inrush that things hold up.

In other places tried there is no DC on the line.

DC is a good culprit as we are talking about multiple dwellings in a single building.

There are 3 solutions I can think of:

1) have a current inrush limiter installed ()this might allow the amp to power up but I bet the transformer will be mechanically noisy)
2) have a DC blocker circuit installed (a rectifier bridge bypassed with electrolytic caps of the right value) We are talking about $15-$20 worth of parts. This is something I would have Cary do.
3) use a DC blocker with the circuitry of 2) in it.

You could test this theory by getting the DC Blocker of 3) and seeing if it sorts things out. If it does, I would have the amp modified by Cary to have these parts installed. Its an easy fix.

Sailcappy,

No I would not use the lightning bare 4/0 ground wire for an auxiliary equipment ground..... That could open up a whole new can of warms.

• I attached a three way strip I had lying around into the end of the extension cord. I then plugged the Cary into one of the sockets and the voltage meter into the other.
• When turn the circuit breaker from Off to On the voltage at the end of the extension cord does not change. It remains at 118 volts. When I press the front button from Standby to Active the voltage remains at 118 volts for the 20 second duration. At that last relay click (at about 20 seconds) the voltage dropped from 118 volts down to 115 volts for split second and then back up to 118 volts.
08-22-12: Sailcappy

Well I would bet the switch/breaker on the back of the unit is nothing more than a main power breaker/switch disconnect.

The maintained contact standby/active mode switch is in series with the rear panel breaker/switch. All amplifier loads are fed off this switch.

The soft start circuit, along with, I would imagine active sequence staging start up, keeps inrush currents controlled from the voltage readings you supplied. A 3 Volt VD on a 50' 16/3 cord is incredibly low to say the least.

Just curious is the multi meter voltage section reading true RMS?

One other test I should have mention is to check the VD with the amp playing music from a dynamic music source with the volume level set where you normally listen to music. IF the voltage were to sag below the safety limits of the amp, because of the VD of the extension cord, the amp could be damaged. If you do the test watch the meter to see if it moves around with the dynamics of the music material. Hard to believe the dynamics of the amp does not suffer because of the 50' 16/3 cord.......

The reason I ask is your friend qualified, confident, to perform work inside the electrical panel of your apartment? Nothing major.... Just move the hot conductor of the audio 20 amp dedicated circuit to another 20 amp breaker on the other Line, leg, bus in the electrical panel. (Providing there are any spares. If there is not a spare he could use a breaker that is being used, for the test.)
jea48

• He said all the wires are live coming in to the breaker box and it is not a good idea to switch them as there is no way to kill the current coming into the box.
Sailcappy

Your friend does not feel safe working on the inside of a live electrical panel and that is fine.....
Better safe than sorry.....

You would need to hire an electrician to do the test for you.

Atmasphere,

The Cary 7.250 has a built in DC blocker as well as a soft start circuit.
Jim

First off, Sailcappy, I (we) appreciate your patience and cooperation with all the requests from "The Brain Trust" (SCRUBS). Other than Jim's latest request(s) below, and based on what’s been tried and confirmed so far, I think we all will agree that an oscilloscope would be beneficial/essential at this juncture to diagnose mutually-suggested D.C. and noise suspicions, of which you mentioned that your friend, who works for the power company (aka;” Ken”), was trying to obtain one.

08-22-12: Jea48 “…Just move the hot conductor of the audio 20 amp dedicated circuit to another 20 amp breaker on the other Line, leg, bus in the electrical panel. (Providing there are any spares. If there is not a spare he could use a breaker that is being used, for the test.”

and...

”I would sure like to know what the VD, voltage drop, looks like at the end of the 50' 16/3 cord as the Cary amp is going through its active start up cycle...... Especially that last relay click you hear.”

Jim, wouldn’t his other “standard 15 amp” outlets, throughout the apartment, be split up between the two incoming legs? He has tried, unsuccessfully, to energize the amp from various 15 amp locations around the apartment, though it isn’t known how they are split up.

Frank

PS; Thanks Jim/Al for the "quoting" assistance. I'll take my sign off.

Jea48, thanks for that note. In that case, I suspect that the DC blocker circuit has developed a malfunction. It would not be missed if the AC line were clean.

Its easy enough to test for. There is someone on this forum who makes AC extension outlets that have the DC Blocker built in. Just use one of those and you would know if that's what it is.

The lack of AC grounds in the wiring is disturbing, but it should not cause any troubles with the amp.

08-18-12: Metro04

"I'd really like *him* to re-check the voltage from the outlet's LINE (smaller slot), to the GROUND pin and report the voltage. He's previously stated there's no stray voltage between the NEUTRAL and GROUND, so I'd like him to check for "resistance" between the outlet's NEUTRAL (larger slot)and GROUND if able."

08-21-12: Sailcappy

“6. Voltage from the “smaller" slot to the "ground" slot is 118 volts.
7. Resistance (Using the Omega setting on the volt meter) between Neutral (Large Slot) and Ground slot jumps between 13 and 17 units.”

08-22-12: Atmasphere

“The lack of AC grounds in the wiring is disturbing, but it should not cause any troubles with the amp.

Atmasphere, This was something I pushed to verify - lacking any knowledge of Cary’s circuit topologies - and *can* be of issue with some equipment designs (audio equipment aside). Sailcappy’s stated measurement of 13-17 ohms seems a tad bit high for 10 AWG, but based on the Neutral wire’s length alone, and various metal conduit mechanical connections, might be expected. Really don’t know for absolute if that amount of resistance poses an issue for that *particular* amp.