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Alesis prolinear 720 active speakers for music production. The fuse has not blown, the lead works fine but the speaker is not responding, it doesn't turn on.

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  • johnnysd Nov 07, 2008

    Same problem here. They just stopped working. First one, then the other. The just won't power up anymore.

  • stacyjones Jan 30, 2009

    personnaly the same thing happened, but i open them up and two components have blown, one is a fuse i believe, but not sure what type, could do with finding a schematic, not sure what the other component is but the same components have blown on each monitor speaker


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Open the rear and look on the amp board (you may have to unscrew and unclip this too) next to the small white clip that comes from the power supply.
if it looks something like this:
then the following burnt out parts need to be replaced:
NTC thermistor 5 Ohm (Farnell part No:- 1704471)
5A antisurge fuse (Farnell part No:- 951620)

upon these parts blowing should protect the rest of the board, so that should be all.....for at least another year.

alesis will either try and charge you £20 per speaker just for parts or try and sell you the whole replacement board for about £100 each.
(the parts are under £2 each)
get some1 with a bit of soldering experience to do it if unsure.

Posted on Oct 14, 2009

  • Brambo Sep 13, 2013

    I have the same problem - no visible sign of a component being blown. No charred elements. Thought maybe a fuse but can't seem to find a fuse anywhere on the board. Any ideas?


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Farmerwardy, you're a star! Was gutted when the one refused to power up today. The power board looks just like the top picture. All the components around the thermistor are a little charred but seem intact. Would you say it was fair to assume they are unharmed? Thanks very much for the info. Much love x

P.S. the part number for the fuse at Farnell has a 4 on the end (Farnell part No:- 9516204). Should make it easier to find.

Posted on Apr 11, 2012

  • farmerwardy Jul 10, 2014

    My understanding is that the fuse blows once the thermistor fries, thus protecting the other componants.

  • farmerwardy Jul 10, 2014

    Also since posting this reply after making the repair myself, i have not experianced a repeat.


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