Amp Shutting Down, need help

Well, one thing that seems to be clearly established at this point is that the problem is related to inrush current occurring at the 20 second point, whether its root cause is DC offset + failure of the DC block in the amp, per Ralph's suggestion (which strikes me as a clever and plausible theory), or some other kind of power anomaly, or oversensitivity of the amp's circuit breaker (even though it has been replaced once), or whatever.

And re the SR Powercell, although there is little in the way of technical detail that is available, one thing seems clear. Its design is based on different principles than most or all other conditioners.

Jim & Ralph, do you think it might be a reasonable gamble for Sailcappy invest either $215 or $239 for one of the BrickWall surge protectors, which also provide some degree of line filtering, and include a "series surge reactor current limiter; cascaded, auto-tracking dual polarity voltage limiters; dual pulse inverters," etc., with the onset of voltage clamping specified to occur 2 volts above the waveform peak. Specs here for the 2-outlet version, and here for the 8-outlet version.

I and a number of other A'goners use one, btw, with no reports of audible side-effects that I am aware of.

Regards,
-- Al

Hm. You could certainly try it. Anything that might drop the voltage a little would probably sort it out. We have ascertained that the issue relates to overpowering the breaker due to something to do with the incoming AC power.

It happens on any outlet in the area; its not related to which side of the line or whether there is leakage from another component. Its entirely to do with the power transformer and the incoming power.

I doubt that its a surge thing- it happens consistently. A surge would only show up occasionally. So I'm going with 'no, that won't help' in this case. Measured line voltage is fine so its not an over-voltage condition of any kind.

This is all assuming that the measurements are correct and the behaviors accurately reported!

Another possibility is a shorted current inrush limiter. A third possibility is that the breaker has developed some residual magnetism and no longer breaks at the right point- IOW its become too sensitive. Simple replacement of the breaker would solve that. Any one of these problems could be such that it would not show up elsewhere due to variables like line voltage and such.

For example if Cary put the unit on a variac when they tested it, the variac may well have functioned to limit the surge current enough so it was no worries. At the other field location, there could have been something with the wiring or the unit was plugged into a power strip with other gear already on it. Power strips only have one power cord, so there could have been a temporary voltage drop, eliminating the problem.

I like to go for the simplest answer as the best one so my thinking right now is the breaker itself is defective.

I like to go for the simplest answer as the best one so my thinking right now is the breaker itself is defective.
08-23-12: Atmasphere

Ralph,

I agree....

I would think both toroidal transformers would have to be the first items powered up on the amp along with the DC power supplies long before that last click is heard.....
I mean the active sequence start up circuity needs DC power to go through its functions. I have no idea what that last click, relay is doing....

I also believe the soft start circuitry of the amp is doing a good job smoothing out the current as the two toroids and DC caps of the power supplies are charging. In fact, because of the 20 sec time frame for start up, both toroids may not even be powering up at the same time.

I was surprised by the voltage load test readings Sailcappy measured at the end of the 50' 16/3 cord with the amp connected.

No load 118V and through the whole active start up sequence the voltage only dropped 3 volts!
Granted the impedance of the 50' cord would limit inrush current..... I still would have thought the VD would have been more than 3 volts.

I mean we are talking about a 7 channel power amp rated at 250 watts @8 ohms each channel.

I think I would call Cary and ask them what it would cost to change out the switch breaker to just a switch and add an accessible fuse holder and fuse on the rear panel and replace the cheap magnetic breaker.

I believe I counted 6 fuses in the amp already.... What's one more.....

A look inside the Cary 7.250 Amplifier.

08-23-12: Jea48 “I would think both toroidal transformers would have to be the first items powered up on the amp along with the DC power supplies long before that last click is heard.....
I mean the active sequence start up circuitry needs DC power to go through its functions. I have no idea what that last click, relay is doing....“

I would speculate that the standby circuit is merely a passive or solid state design (no transformer) to minimize idle/standby current - fed after the magnetic breaker, which then feeds the delayed progressive interlock power-up circuits, which then controls the toroid’s power relays where any “soft start” circuitry might be interfaced, or something along those lines.

“I was surprised by the voltage load test readings Sailcappy measured at the end of the 50' 16/3 cord with the amp connected. No load 118V and through the whole active start up sequence the voltage only dropped 3 volts! Granted the impedance of the 50' cord would limit inrush current..... I still would have thought the VD would have been more than 3 volts. I mean we are talking about a 7 channel power amp rated at 250 watts @8 ohms each channel.”

I would have expected a larger dip as well unless it *was* slightly larger, but the refresh-rate of the meter was too slow in conjunction with a very short soft-start period (milliseconds). Granted, all outputs were unloaded, but the size those two toroid’s KVA rating would commend a substantial inrush without a soft-start. Orrrrrr, I'm betting because the mag-breaker tripped before the meter read the actual larger voltage drop.

Which now gets to Ralph’s speculation regarding the mag-breaker’s condition. If we knew what the typical (unloaded) inrush current was after the 20 second delay, within an ideal supplied AC scenario, we would have a better idea how close we’re getting to a *healthy* breaker’s 15 amp trip threshold vs. sailcappy’s suspect breaker.

Frank

Orrrrrr, I'm betting because the mag-breaker tripped before the meter read the actual larger voltage drop.
08-23-12: Metro04

Hi Frank,

The magnetic breaker doesn't trip when the 50' 16/3 cord is used.

Which now gets to Ralph’s speculation regarding the mag-breaker’s condition. If we knew what the typical (unloaded) inrush current was after the 20 second delay, within an ideal supplied AC scenario, we would have a better idea how close we’re getting to a *healthy* breaker’s 15 amp trip threshold vs. sailcappy’s suspect breaker.
08-23-12: Metro04

Agree.....

I asked Sailcappy in an earlier post, I believe, if his friend had a clamp on amprobe to check the current draw of the amp through its start up cycle.... The meter would need to be a true RMS.

His friend would need do a little surgery on an old short power cord carefully cutting away the outer jacket exposing the 3 insulated conductors inside about 6" to 8" or so.

For the test.

The Cary amp plugs into the short power cord.
Clamp the Amprobe around the exposed insulated hot conductor.
Set the Amprobe so it will lock onto the highest reading.
Plug the short power cord into the wall outlet.
Fire up the cary amp.
The Amprobe will lock onto the highest ampere reading just at the point the magnetic breaker trips.
.