RB 1090 went POP,flash,snap...

[AB11]

Turned on the 1090 and got a Pop, flash, snap sort of thing from the left side very close to the front of the chassis area. I could see the flash/spark through the venting and hear the pop snap. There was no smoke and only the slightest smell. The smell was gone instantly. It did not smell like burning material, more like that spark/ozone smell.
The amp seems to be fine after these fireworks. The protection circuit never tripped and it has been on and off 2 times since and it's behaved normally each time. I cannot tell if there is a sonic diffrerence.

Any ideas on what the heck that was? Far left side near the front of the unit very close to the vent holes area.
Scared the crap out of me. I thought the thing was toast. ( maybe it is...)

[Kevin D]

Dead (dead now?) bug? Very few things can blow up and keep on working like normal.

Kevin D.

[AMPER]

ouch...doesn't sound good

:blowup:

[Azeke]

I would unplug the RB-1090 and investigate the internal workings just to be sure, but that's just me.

Peace, blessings and Happy Holidays,

Azeke

[soundhound]

As Kevin said, if it were a component failure it would be dead. If it were me I would pop the cover, and as Azeke recomended, give it a good visual for arc marks, loose wire floating, kids dropped something conductive through one of the louvers, odds are you will spot it.

[AB11]

Thanks for the reassurance. The unit has been doing ok but now I hear things. I suspect it's paranoia but there have been some pops through the speakers that seem to be new. Switching the source on the Denon prepro now elicits a pop through the left speaker ( maybe both?) that I don't remember happening before.

I was hoping someone might have an idea of what component - output relay, overvoltage circuit, etc might be located in the area of the spark.

I will open the unit and have a look. It's just that the damn thing is so heavy and the speaker cables are such a pain to get to that I hesitate.
I have looked through the vents to the general area of the spark and could not see anything unusual.

Is there a pic of the inside of the 1090 on web somewhere so I might identify anything I find once I do get inside it?

Thanks

[soundhound]

AB
The weight of it is what keeps me from pulling mine out of the rack, pulling the cover, and having a look see.

[AB11]

I am glad I am not the only one then.

I think I know what caused the short.

In the area of the spark there is mounted the front most power transister. Just below this and a bit to the rear is a large white stand up resistor(?) that has a much smaller resister mounted very close to it. The white resistor's leads are bent such that they come within less than 1mm of the other resistor's leads.

I suspect an inrush voltage on powerup and an arc here. I can't see any discoloration but it seems the only likely spot for a spark.

I haven't opened the case yet. This all from looking through the vents.

[soundhound]

If that output xistor would have shorted your'e protection circuitry would keep you from listening, and the smaller "bias" resistor would have opened up. That large resistor is probably the emitter resistor for that output xistor. From the sounds of it you would know what burnt resisitor smells like, carbon has a distinct smell, as do many components. Hopefully all is well with it, it would suck to be with out...........

[AB11]

Blast. It's done it again but this time without the spark - only a good, distinct POP.
I suspect it is the inrush current limiter doing its thing.

Here is a question; When I turn on the 1090 there is normally a load buzz that goes quiet after about 2 seconds. Then the protection circuit relays click off and its business as usual.

I assume this buzz is the inrush limiter.

Am I correct?

The POP comes from the same area as the buzz AND when the unit has popped there has been no buzz. ( just the sound of my gasping in terror).

I have a new preamp that has what appears to be a high output voltage. I haven't measured it yet but it has about 20 dbs of gain and it drives the 1090 very easily. I am wondering if this might be contributing to this wierdness - especially since this POP has only happened with this new pre.

So, has anyone blown up a Rotel inrush limiter?
Any ideas?

[soundhound]

The buzz may just be the power supplies (caps/ transformers) gettting ready to go to work. Rotel may or may not have bleeders on their power supplies, if they do the caps need to be charged on every power cycle, which as you know gets pulled through the transformers. You will hear them momentarilly (humm/buzz), that is normal. They may use movs for spike suppresion, but doubt they have current limiting out front. You could try leaving the amp in stdby, bringing it up on the 12v trigger, and see what that does. They may use a pretty good sized relay for "power" to stage it as well as the "protection" relay. Protection circuits will not only prevent d.c from trashing you're speaks, but prevent that nasty "pop" on power up. Another option if not the 12v trigger would be manually turn your'e pre on first, with delay, then the 1090. Divide and conquer.

[AB11]

The buzz phenomenon is not normal. The snap, pop is not normal either.
Normal lam rattle as the toroid transformers load up is about 1/10th the volume this is. And there is no way the crack, snapple, pop is not a problem making itself known. This isn't some gentle buzz. Heck, I have checked my fire extinguisher just in case. Seriously.
I am just going to assume the amp has a problem and call Rotel.
I hope they can tell me what's happening and what to expect in the future.
It's under warranty. I suppose I could live wthout for a bit. Grrrrr.

The 1090 has no 12 volt trigger so I am just leaving the 1090 on 24/7 right now. It sounds great as long as it's not being turned on.

[soundhound]

Certainly sounds like a problem, and a no brainer being its under warranty.

[AB11]

What does a slow blow fuse do when it's slow blowing?

I just noticed a fuse in the general area of the noise and fireworks.

Update - if anyone cares...

It's not a fuse.
Last night I had a long look at the 1090 schematic and found the soft start/inrush circuit. It's built from two thermistors and two resisitors.
This morning I opened the chassis and made my way deep into the belly of the 1090 and discovered some debris. Damn...

A few minutes of disassembly and the poor charred and shattered SCK0512 was in view.

Now what? I suppose I can just replace it and carry on.

" Hello, Rotel service? Can you help me?"

[mmpeak]

Hmmm, did you ever get it fixed?

[AB11]

Yes. Fixed under warranty by some fine folks who, at first, found nothing wrong. After some encouragement, the part was ordered and replaced.