Question about Music
The Amp is brand new I bought from Musicians friend and it keeps blowing it's fuse
You are either trying to: (A) push it too hard, (B) using the wrong type of fuse -- should be a "Slo-Blo" type, or (C) it has internal shorting or voltage modulation and requires service.
Posted on Jan 14, 2013
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Posted on Jan 02, 2017
Try running the amp with no speaker cables connected. If it doesn't blow the fuse you know it's either your Speakon cables or the speakers themselves that are to blame (it's usually the cables)
If it still blows then there is a more serious problem with the power section.
Posted on May 28, 2009
The fuse blows because of a short in the Power Supply. The power transformers primary windings are probably shorted. next in the chain would be a bridge rectifier or a quad of diodes forming a bridge rectifier with a couple surge diodes off of the filter caps. so if you can disconnect the power from the amp, on the power tranny disconnect the primary wires ( the input AC power wires) usually white and black and take an OHM reading with a mulimeter accross the white and black wires. you should get a reading of 15 ohms or higher up to 30 or so. if so the primary windings are good. so then check the secondary (output windings) red and red yellow, etc. ohm reading and you should get a relatively low ohm reading 2-6 approx. if so its a good tranny. on the primary side if you get a real low reading for ohms , like 1 or something, its toast. once you rule out the tranny, switch your digital mulitmeter to read diodes (in the ohms area looks like a diode symbol (a line and a solid triangle with the line being at the tip end of the triangle). desolder one leg of the diode and put one probe on one side and the other probe on the other side. it should only ring out in one direction. you will be testing approx 6 diodes in this power grid on the pcb. you can also desolder the filter caps after you safely discharge the voltage with a 1 ohm 1 watt resistor to ground and use an analog volage meter to see the needle rise in one direction and not in the other (switching the test probes from one side to the other on the cap). usually what i do is just spend 20 bucks on all those parts from mouser.com and instead of desoldering to test i desolder to replace with new. diodes usually part number 1N4003 or 1N4004 somewhere in that ballbark. hope that helps. i think its your power tranny primary winding that is shorted, be aware that this might domino effect into the rectifier and caps, so expect to replace them. its super easy!! you can email me from my website yostamplifier.com
Posted on May 07, 2010
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