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Deftech BP3000TL speakers and UPS don’t get along


(More in the way of ignore the election by posting random stuff). Well I have a 20 year old pari of Def Tech BP3000TL speakers. Back then they were monsters weighing 150 pounds plus each and standing over five feet tall.

They also have 1,000 watt amplifiers in them for 18″ subwoofers which is pretty incredible. I finally used them again and they worked fine, but today when I turned them on the amplifiers would not.

In looking through the Internet, these speakers use low-cost Class D “Plate Amplifiers” and they have a history of failing because of cheap parts thost in-speaker amps fail all the time. they are all of course out of stock now so I though I was completely screwed.

So the solutions are not great. The internals are easy to remove, but the subwoofer is a 75 ohm one (so it needs a special amplifier). The main solution seems to be to pair each speaker with it’s own subwoofer so at least you can still use the mains and the treble units and not throw the whole things way.

But….. then I unplugged one and left it and it suddenly worked! On a hunch, I realized I had just plugged them into an APS UPS and when I just plugged them into the wall, they worked fine. I’m not quite sure why that is, but I suspect that the waveform this cheaper UPS but I wonder if on transient, this little UPS could not put out enough power. After all, with 2kW worth of draw, that is a lot for a computer sized UPS. I wasn’t playing it loud, but I wonder if on startup there is a transient and the protection circuit meant it wouldn’t start.

I did check the fuse in the amplifiers and they were ok. So o think the issue is perhaps in power up where the self sending amps don’t power on or in the way surge has happened.

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