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Amps compressing after 6 hours

Amps compressing after 6 hour

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#1 dpiccioni

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Posted 07 August 2014 - 04:26 AM

We are a beach restaurant and have 2 x Crown CD1000' s powering 8 Bose 251 speakers. Purchased 2013, they worked great. This year 2014, after 6 - 7 hours playing, they both start to show red thermal lights even though they are not warm. The sound then compresses. This happens to both amps at more or less the same time. We use the amps the next morning and they are fine again until the same hour when the same thing happens. We do not change the volume throughout the day. The volume is low throughout the day, at about 15-20% of the output capability. During the problem, if we restart the amps we receive a 'lo line' message, then the amps start and the same thermal light/compression problem kicks in immediately. The amps are not outside, but are exposed to sea air. All signal issues arriving at the amps have been double checked. Shorting of speaker cables doesn't seem to be the problem. Any ideas?
Amante Ibiza

#2 Patlover1983

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Posted 07 August 2014 - 07:13 AM

The lo line message indicate there could be something wrong with the AC power. Have you allready try to connect one or both amps to a different AC source?

Maybe the AC wiring is to thin, it runs hot (after the 6 a 7 hours) and the resistance is getting higher?
Or maybe you have another device running at the same group that draws excessive power away from the AC source?
I also own 2 CDi1000 amplifiers but never seen this behaviour before.

#3 joust

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Posted 07 August 2014 - 12:22 PM

As Patlover (you should sign your name!) states, it is very possible that the AC line has difficulties to supply power/current at particular times. LO-LINE also means that the internally generated rail voltages are not stable and possibly erratic. Perhaps some air conditionner fires up or something. We must not forget that an SMPS (sample mode power supply) is current dependant and if the current can't be supplied to the SMPS it will not generate the proper rail voltages.

One solution is to use an uninterruptible power supply. Secondly, find the current hog that powers up at the odd time and change its AC source. Thirdly, and perhaps only as a long shot, the amp is problematic! Let's say I doubt it at this point, because of the time line : The amp seems to fail at peculiar times!

Alain

#4 dpiccioni

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Posted 08 August 2014 - 05:19 AM

Wow, thanks guys - after 2 months of trying, this seems to have solved the problem. We fed current from a different phase, and put the amos on a UPS supply and it has worked immediately. Seems the restaurant fridges were all kicking in more as the day got hotter, then restaurant lights all come on at 7, so that must have been it. Thanks again
Amante Ibiza