Mackie SRM450 repair kit active speaker/monitor

If there is a defect in the primary supply for the 380V, the FET transistor Q21 usually has a short circuit. The fuse is then also defective.

The PWM controller U36 should then be replaced preventively together with the Q21.

I offer a set with these components here:

1x U36: UC3842, PWM controller

1x Q21: 12N60, N-Channel MOSFET TO-220F

I don't offer fuses here as they vary depending on the country: 120V: 6.3A, 230V: 3.15A.

After the purchase I send a message via eBay with a download link for files such as: schematic with assembly drawing and data sheets as PDF.

The device must be opened to replace components. Attention, pull out the power plug! Be careful, electrolytic capacitors can contain dangerous voltages! Wait long enough for the tension to be discharged. Photos help to screw the many screws back into the right place at the end. Desoldering the components requires soldering knowledge and suitable tools and equipment. Make sure there are no other shorts on the board.

Pay attention to the marking before inserting! Don't forget the ferrite when installing. Remove this from the old FET.

When assembling, ensure that the insulation of the FET components is undamaged. Subsequent errors caused by the short circuit cannot be ruled out. I decline any responsibility for any damage.

No guarantee

No Return

Shipping takes place from Switzerland.