“You can listen to it but I wouldn’t leave the room with it left on” is what my tech told me about my HH Scott LK72 before all the refurb parts came in.
What went bang, smelled of "I'm fried", yet left it in working order...???
Hi gang - wasn't sure if this should go here under amps or tech talk, but here goes: normally, I'd call the salesman I work with at my LAD, but they're closed Sun. & Mon. and I'm loosing sleep over this as I feel I'm on very thin ice.
My wife and I were watching a movie late last night, and after the movie we were sitting on the coach discussing it when we both jumped when we heard a loud bang coming from the media console and smelled an electrical burn. Sitting on top of the console is a Dan D'Agostino Progression Stereo power amp, a McIntosh C53 preamp, and mounted directly behind this on the wall, a Panasonic plasma TV.
Nothing tripped a fuse, the TV was still on, both sets of power meters on both the Dan & Mac were still lit. I streamed a test track that has a lot of bass that when I turn up to a certain volume, has the Dan's power meters hang at 400 watts for a few seconds, and they did - just like always. Everything seems to look and sound fine.
So, while I'm not asking for anyone to try and guess which of those three components made the bang, what I am asking is for any of you here who have an electronics background tell me what electronic part (in either the preamp, amp or TV) possibly could have made a loud bang releasing an electrical burn smell, yet "seemingly" leave everything still functioning as normal...?
--thanks and cheers!
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SoundArtist SA-200IA integrated. NIB, set it up and bang, a loud popping noise from the amp and speakers. Intermediately turned it off. Could smell a bit of burning and something inside definitely blew as I also heard debris fling around in the box. Hooked up a second set of speakers just to see if the unit still worked and it did. For the price it sounded ok. Send it back and tried a couple of others in hopes they'd be fine but each had some popping,noise when hitting buttons, especially tone control defeat button, albeit nothing like the first experience. Chinese made but supposedly "British" designed, with some decent reviews so I figured I'd try it. Sent all back and should have left a harsher review on site. IMO, they have some QC work to do and weren't forthcoming on realistic specs.
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@imhififan -thanks. Yes, I had figured that was the MOV and it looks just as shiny and new as in the pic you posted... So, it's even more baffling now that you confirmed that is the MOV. -cheers |
if you can find the culprit (it ought to be visible) and can get a schematic, i will take a quick look and if i can figure it ouy, tell you my opinion.
I get it, i just know most people are flummoxed w/r/t the how and why - and by people i mean techs and even engineers that dont spend a coupe of hours learning the context ( and an hour of n engineers time is worth.....?) |
@itsjustme thanks. I'm planning on calling my LAD salesman when he's back in the office to discuss. I looked inside the D'Agostino and no smell, no carbon, no swelling, etc. (just a little bit of dust that got through the top vents). The biggest problem is figuring out where it came from - based on the direction of the sound, it's either the D'Agostino or plasma TV. If the D'Agostino was light enough for me to pick up and throw in the back of my car, even without seeing anything or even sure if it was the culprit, I'd just do it and drop it off at my LAD... but, at 125 pounds, and an awkward carry because its front heavy, and having to go down a full flight of stairs, it will take some planning and arranging helpers. -cheers |
you have the likely culprits. MOV, capacitor, possibly the safety cap.
So the next question is "why?", "what did it do?" and ho to replace. Obviously the repair is influenced by why a cap failed. There are cues for anyone who knows the design int he fact that its still working. Sometimes products are in parallel and one can go. Sometimes they are intended to filter out noise in certain places, and maybe a 2nd order impact on performance/sound. But they are all there for a reason.
Let’s establish one fact: electrolytics capacitors are not the world’s most reliable parts. They die early. They die without obvious reason. The one predictable failure mode is old age, but your products are far too new. I am offering recap on some series of stuff i designed 30 years ago - and the vast majority are still in service. 5 or 10 years old is nothing. By way of contrast, I just got shipment of high quality 100v parts all of which fail at around 20V. QED.
I’d really hve someone who knows the design at minimum diagnose the reason.
One more possibility: an insect. Insects can become conductors if the voltage is high enough they might go bang themselves or possible conduct change voltage levels or loads and make a capacitors go bang. Seen that!
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There may be very little left of what ever blew up. Open the cover and look for two short wires sticking up from the circuit board or wherever the parts are concentrated. Electroltics and varistors are relatively cheap. Also look for where the power line comes in. Don't run it without getting it repaired. Something really expensive might go as a result of whatever popped. Good Luck. |
@tubebuffer said ”Call neighbor ask if they have Raven amp. Tell them contact reverend. Problem solve.” 😂 |
Possibly a MOV. They look like disk capacitors but are basically a surge suppressor built into the gear. When a brief spike hits the power line they momentarily short-circuit. This sounds like it would blow the circuit breaker but it happens and releases so quickly that the inductance of the wiring absorbs it before the breaker can trip. On a heavy spike they can "punch through" with a bang and a slight odor of electrical arc or ozone. |
@closenplay Thanks - I didn't smell anything around the plasma, but I'll check out the audio section on the plasma and see if it's still working, because yes, I never use it anymore. Boy, that sure would be nice if that's all it was. -cheers! |
Another possibility is the audio section of the plasma tv which will be energized even though you are routing the audio through an independent sound system. Of course, if the plasma is a monitor only there is no audio section. Give that plasma a sniff. Easy for reflected sound to fool us into thinking it came from a different location from the origin. |
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Most likely the power amp varistor. It's got a 2kv transformer with 0.1 Farad power supply capacitance. That shorts a lot of current and the MOV has to be pretty substantial. My guess is what you heard is the MOV cracking under stress. Best to get the amp checked to make sure the fault wasn't internally generated. |
@wlutke Thanks - that sounds like it’s at least on track with what I’m experiencing. Just wish there’s a way to tell if it was the preamp or power amp that did it, but I’m guessing it’s the power amp… |
Well if it lost a cap in one of those boxes you'll smell it from the vents on the box. Make no mistake. It will stink. Let your nose tell you where the problem is. Don't disregard something else being the culprit either. Follow your nose, touch with the back of your fingers, not the front.. Be safe ay.. I'm kinda glad you smelled electrical stuff. No one is shootin' at ya. Friggin wild west anymore. Regards |