What size internal fuse on mackie srm450v2 speaker

There are repair services on ebay etc but not cheap.

Bad FET circuit or leaky cap.

Do you have the existing resistor, Larry? Is it crisped up, or can you still read the colored bands? Those colored bands are a color code indicating its resistance - if you can read them off here, we can tell you what its resistance is.

As to wattage... that's something we could at least estimate from size & shape, weighted a little by speaker wattage rating (that resistor should never see as much wattage as the rating).

Last... if we knew for sure what every other component is (from its printed labeling), we could reconstruct the schematic and calculate that resistor's value. Reverse-engineering a crossover designs is far from being rocket surgery. 8)

I offer these as alternative approaches; it may be near-impossible or impossible to get that schematic.

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.

I believe there is an internal fuse in these which, according to a friend who has these, seems to blow occasionally for no apparent reason. He has also had to send two back for replacement and would not buy again, they seem to be inherently unreliable although they sound great.

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.

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!

Chances are if the fuse has blown, there are failed electronic components that caused the failure.

Here is a service manual that will be CLOSE to your unit, though not exact:

http://elektrotanya.com/mackie_srm450_active_speaker.rar/download.html

Scroll down to the "Get Manual" on the site and click on the link. The file is compressed. The first part is the schematic, the second the assembly and parts list. Likely the main low freq power amp has shorted transistors.

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