Dave Barnett wrote on Tue, 11 October 2005 13:09 |
Why is it that when I lose a channel of an amp, it's never during a show, but immediately upon system power-up in the afternoon? I really hate that feeling of "uh, that was working fine last night". |
Dave Barnett wrote on Thu, 13 October 2005 02:22 |
To elaborate -- (1) This is in a fixed installation, nothing is getting moved. (2) The amplifiers in our rig are all Crown Macrotech 5002, 3600, and 2400. The Macrotechs all have some sort of internal power up sequence, so it's not the same as an old amp where you're hitting the transformer, diode bridge, and filter caps as soon as you throw the switch. (3) I agree that the afternoon is the most convenient time to deal with this problem, but it's still frustrating. (4) The failures I experience are generally blown channels, i.e. failure of multiple output devices. Tuesday's failure marks the fourth time this 5002 will have to be returned to Crown for service. If the amplifiers were failing in service, at least then I could point to specific conditions and say "that's why it failed". Like for example guest BE slamming the hell out of it. |
Dave Miller wrote on Thu, 13 October 2005 08:55 |
This is not directly amp-failure-related, but I once had to sort out an install where the supply breaker occasionally tripped due to turn-on surges. Replacing it with one that had greater surge-handling capacity cured the problem, but I did wonder why it only happened infrequently. Apart from the fact that the surge current was probably only bordering on the breaker trip threshold, I thought of two other explanations: (a) ambient temperature - if everything is cold (eg no building heating) then the resistance of copper (including that in the amp's transformer as JR mentioned) is lower, so switch-on surges might be higher (b) the exact point on the 50Hz (60Hz in the USA) mains cycle that equipment is switched on. If this is near the peak, then wouldn't the surge be greater. I wonder if either of the above could contribute to occasional power-on failures. Or I am talking nonsense?? Dave |
Dave Barnett wrote on Thu, 13 October 2005 00:22 |
(1) This is in a fixed installation, nothing is getting moved. (2) The amplifiers in our rig are all Crown Macrotech 5002, 3600, and 2400. The Macrotechs all have some sort of internal power up sequence, so it's not the same as an old amp where you're hitting the transformer, diode bridge, and filter caps as soon as you throw the switch. (3) I agree that the afternoon is the most convenient time to deal with this problem, but it's still frustrating. (4) The failures I experience are generally blown channels, i.e. failure of multiple output devices. Tuesday's failure marks the fourth time this 5002 will have to be returned to Crown for service. If the amplifiers were failing in service, at least then I could point to specific conditions and say "that's why it failed". Like for example guest BE slamming the hell out of it. |