Archive for April, 2008

Repairing Alesis M1 Active mk2 Monitor Speakers

Wednesday, April 30th, 2008

For Friday’s show, we used Alesis monitor speakers that we had in the lab, plus Steve, one of the students, supplied two.

Alesis M1 Active mk2 speakers

During installation, one of the speakers started winking its blue power light and ceased playing sound, and before the show another did as well. Steve found a Studio Central forum post suggesting that the problem was due to a failed electrolytic capacitor that gets baked by a hot resistor right next to it, and a quick peek inside confirmed that it was a likely explanation and fix.

Alesis M1 Active mk2 speaker, circuit boards and interior

After unscrewing, the back panel lifts out and reveals the power supply board mounted vertically on a metal shield, and the crossover/amplifier board mounted flat on the panel.

Alesis M1 Active mk2 speaker power supply board

The naughty capacitor, C8 (actually its replacement after I finished), is in the center red rectangle next to the offending resistor. Another bad electrolytic capacitor whose number I forgot to catch is featured near the top of the board. Both of these tested bad with my Capacitor Wizard in-circuit equivalent series resistance (ESR) tester; all of the other electrolytics on the board tested good.

It was simple work to remove and replace the two capacitors on each board, and it brought both speakers back to life. Thank you, forum posts and Capacitor Wizard!

BTW, are electrolytics supposed to look like this?

Leaky electrolytic capacitor

Two caveats about this repair. First, I should have used 105°C capacitors, but I could only find 85°C caps on short notice, so these will fail quickly and need to be replaced again. At least now it’s known exactly what needs to be done. And second, the forum post suggests moving either the resistor or capacitor to get them further apart, which is a great idea but which I haven’t done yet. I’ve been trying to think up a clever way to stick a little heatsink on a vertically-mounted resistor, which might be a better solution yet.

First Pictures from Wired 3: Please Wait

Tuesday, April 29th, 2008

Wired 3: Please Wait gallery photo

The videographer’s pictures of Friday’s show are back and the album is available here:

Two notes:

A minor point, the PA system in the corner of some of the pics wasn’t supposed to be there and the projection looked much cleaner without it, but we had trouble with Pd locking up while throwing sound across the network and brought in the separate PA for ambient sound at the last minute (SFX still coming out of the 10-channel system).

And the class is preparing all of the materials from the show and putting them online, so I’ll have a followup post when they’re all available.

Wired 3: Please Wait (Friday Night!)

Wednesday, April 23rd, 2008

I haven’t posted anything in a long time because I’ve been:

  1. Lying on a beach in Jamaica.
  2. Hauling off treasure troves of vintage electronics components from a secret lair off of Highway 77 in northeast Kansas.
  3. Utterly consumed by working with our Technology: Art and Sound by Design students to get our final show ready for Friday night.

You guessed it; it’s option C, which WordPress’s stylesheet renders as 3.

We’re taking over WSU’s Shift Space gallery for April’s Final Friday gallery crawl. We have ten projectors covering the gallery walls in 360° video surround and displaying a giant, abstracted circuit in sections like this:

The student technology projects (abstract LED display, traffic light and control button, computer-controlled archival video footate, floor pressure plates) interface with the “circuit” to control fireball “bits” moving about on the wires and through the gates. Another student has prepared ten-channel audio with both spatially-located sound effects for circuit elements and ambient sound/music to set the tone for the show.

All electronics are done on Arduinos (probably about six in use for the whole exhibit); and PC interfacing, circuit control, and audio are done in Pd.

If you’ll be near Wichita Friday night, I’d love for you to drop by and introduce yourself — ask around for Keith and someone will point you to me.

Shift Space is at 800 E 3rd St N, and we’ll be open Friday night only from 19:00 to 23:00.