I have Mackie SRM450v2 speakers, one has no power, I think the fuse has blown, it it possible for me to change this myself? The manual says it's not user serviceable.

There are repair services on ebay etc but not cheap.

Bad FET circuit or leaky cap.

There is almost certainly a reason the PSU has blown, these are not very reliable units and the amp has probably gone and taken the PSU with it. You are better off taking it to a dealer and getting it fixed. If there is no power on the seecondary and there is no short the transformer must have blown (assuming you're not trying to check with a DC meter)

take it to a Sound Production company and ask their opinion. If they use Mackie gear-even better. They will better be able to tell you what's goin' on if they hear the speaker. Good luck.

This speaker at full power draws average 1.3A at 230V and 2.5A at 120V. Mackie's recommended fuses are in line with this so your fuse is actually too high a rating. It is possible you are using cheap fast blow fuses or are over-driving the speaker (which should cause the fuse to blow) These speakers are only capable of 118db sustained (@1M) so cannot be expected to cope with anything but small venues or gentle music.

Make sure you are driving LINE LEVEL signals to this and not mic level signals.

It would be very unusual if the blue LED is burned out. They should last a million years. I suspect the power supply has a problem.

Mackie say this is not a user service part. If the fuse has blown there is probably a fault in the unit being their reasoning. I know for certain they tend to blow for no apparent reason so it is worth giving it a go. They are 5 x 20 Slow or time fuses. 7A for 120V and 4A for 230V

If you've changed the tweeter and the sound is still muffled the fault is with the HF amp, or the cross-over. You will have to send the amp assembly for repair as it is all surface mount components in there -nothing you will be able to fix yourself. Sorry for the bad news!

There is an entire crossover circuit inside that is BEFORE the amp section. There are 2 separate amps: one for HF and one for LF. Can you describe the noise you are hearing in more detail? Is hte sound effected by the gain controls at all? What happens without any input?

Thanks,
Dan