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Pulled the rig out for a graduation party today. Sounded phenomenal for hours right up to the last tune, at which point my amp running the otops blew. Like sparks and all. Will be interesting to pull it apart and see what happened, since I still wasn’t even into the limiters, tops or subs.

Oh noo!
At least it survived the gig
What amp, one of those Crowns?

Ooooh, das no good! I hope you can find the cause!
You know, the first thing that I think of is high frequency oscillations. Are the 4 ohm resistors in good shape, and power has to run through them...not bypass? Is the setup in the photo the way it was run? If yes, were high frequencies boosted?

Yep, the Crown CH is what I run the tops with. Two CEs bridged to each run a pair of subs. Pulled the CH out of the rack and replaced with an identical spare amp . Opened up the blown one expecting to see something burned or popped, but everything looks fine. Based on where I saw it spark, maybe it was the board that has the clip and protect lights? I'll have to see if our local repair shop is even still around - I think they might have shut their doors during the pandemic.

There aren't many items that would create a spark, as that would require a fair voltage. Most faults would cause the protection circuitry to kick in before damage is done.

Have you tried the amp again? I had a Crown go thermal several years ago when one of my OTops had a blown cap in the crossover. I'd test it with one OTop at a time. You might find the amp is still working.

If not, then I'd ditch the 40 pound amp and get a newer model Crown XLS.....you can find 'em used pretty regularly.....and you'd save 30 pounds in your rack. Probably cost the same as trying to repair the old one.

Bruce Weldy wrote: ↑Sun May 08, 2022 12:54 pm Have you tried the amp again? I had a Crown go thermal several years ago when one of my OTops had a blown cap in the crossover. I'd test it with one OTop at a time. You might find the amp is still working.

If not, then I'd ditch the 40 pound amp and get a newer model Crown XLS.....you can find 'em used pretty regularly.....and you'd save 30 pounds in your rack. Probably cost the same as trying to repair the old one.

I actually haven't tried to power it back up, but will give it a try. Thankfully I had another amp I could just slot in its place for now. Yes, they are heavy buggers, but normally stupid reliable. Since they are in a rack on wheels, and I roll it right into and out of my little trailer on a ramp, it's not too big of an issue. At least until I get one of those gigs with flights of stairs to navigate...

Another interesting thing. I had one set of otops cutting out now and then. Very infrequent, but very annoying. Finally figured out it was the cable and pulled it apart today too. I thought it would be with the terminations in one of the speakon connectors, but it is actually the red wire. Continuity meter just kind of weakly squeaks on the red, fine on the white. I don't think I've ever had a cable wire go bad somewhere in the middle. Jacket all looks nice, no cuts/dents/abrasion. Oh well, at least that's one more little issue resolved.

himhimself wrote: ↑Sun May 08, 2022 3:45 pm
Another interesting thing. I had one set of otops cutting out now and then. Very infrequent, but very annoying. Finally figured out it was the cable and pulled it apart today too. I thought it would be with the terminations in one of the speakon connectors, but it is actually the red wire. Continuity meter just kind of weakly squeaks on the red, fine on the white. I don't think I've ever had a cable wire go bad somewhere in the middle. Jacket all looks nice, no cuts/dents/abrasion. Oh well, at least that's one more little issue resolved.

I've had that happen with instrument cables every now and then because they get stepped on. In fact, almost every cable I've fixed that had a break in the middle was about 4-7 feet from the end ...... that's where the guitar player steps on it over and over. It's a little more rare for mic cables, but can happen.

Speaker cables? That's really rare....especially it it's a heavy gauge like 12ga or 14ga.

This is just a wild guess; but do you think something flew inside the amp to cause it to short out? Like a bug?

jimbo7 wrote: ↑Sun May 08, 2022 7:01 pm This is just a wild guess; but do you think something flew inside the amp to cause it to short out? Like a bug?

You know, jimbo, it crossed my mind that night. A big crane fly or wasp or some other insect getting fried in there, but it wasn't a buggy night at all. I need to try and fire it back up today and see what happens.

My mind immediately goes to blown capicitors. But, if you say there's no evidence... hmmm.

I look forward to the conclusion of this mystery!

I'd completely enjoy a high res photo of the board next time you're in there.

Plugged it back in and turned it on. The power and channel 2 clip light come on. Both fault lights are blinking. The manual doesn't say anything about the constant clip light, but the flashing faults have the following potential issues - "The amplifier output wires have developed a short circuit.•The amplifier output stage has stopped operating. If so, return the unit to a Crown Authorized Service Center"