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The original was posted on /r/askelectronics by /u/23492349283491346387 on 2023-08-07 19:54:48+00:00.

Here is a photo album of the damage:

Model is Q108b, these are class ab bi amped active monitors.

I bought these powered studio monitors for reduced price from someone who says they were using them and one of them randomly started smoking, and the other one failed the same way shortly after. These were extremely expensive speakers back in the day, and still worth a lot now, and I would like to take a crack at getting these to work.

They mentioned they suspected it might’ve been a bad cable, but that seems odd for 1 cable to have been used with 2 monitors, so I’m not exactly sure what’s going on there. Also something odd is that they said that the 2nd speaker failed a few days later, but why would that speaker be in use after the first one did? Maybe they continued to use the failing speaker? Not really sure what’s going on there and there was a language barrier so I couldn’t really clarify.

Anyway, I have checked all 4 drivers with a multimeter and they all seem good, no resistance on the woofers.

Upon opening them up the same module is fried on each speaker. I don’t see any other damaged or swollen parts, and all the internal fuses, and the main fuses look good.

Does anyone have any insight as to what may have happened here, and the chances of getting them repaired?

This is a boutique speaker from the early 90s so I suspect it will either be impossible or extremely difficult to find replacement modules. I am able to do basic soldering but this is almost certainly beyond the scope of my capabilities to repair unless I can swap the modules out. I have written to Quested and am waiting to hear back.

Is this worth bringing to a speaker shop and if so, what should I expect to pay to get them properly working again, in Canada? Thanks!