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