Alesis M1 MkII Active amp assembly failure at D1 diode

[dpd7]

My question, in short, is: does anyone know what part the diode D1 is on the amp assembly board in the Alesis M1 MkII Actives? It is a tiny little thing with some lettering I can barely make out, but appears to read IISF, 8SF, RSF, or BSF...

The details follow.

One of my M1 monitors stopped producing sound recently and after some testing I found that the problem was a blown (open) diode, labeled D1, located between the two LM amp chips.

D1 is part of a small cluster of other resistors and transistors (R8, R9, R10, R11, Q1, and Q2) that go to pin 8 of the woofer LM3886T amp. According to the datasheet, pin 8 controls a "mute" feature on the chip. This would go a long way to explaining why my speaker just... went mute one day.

It would be good to know how to fix this, because the amp assembly in the other (working) speaker looks just like the one that failed, that is, the whole area around the diode/resistor/transistor cluster has baked a nice big brown spot into the silicon. Further, both power boards have their own matching baked spots. I think this indicates multiple design flaws in the Alesis M1 MkII Actives, and I'm just waiting now for other components to fail. My speakers are ~6 years old, but regardless of age those parts shouldn't be getting hot enough to bake the board.

A pity, because I love the sound of the speakers!

Please share with me your comments, part numbers, schematics... Thanks!

[Enzo]

Did you contact Alesis directly and resquest a schematic?

[dpd7]

Not yet, but I'll contact them next week and post how the request goes...