"Burning" SX-990

[Ohighway]

Got a set of freebie Utah speakers today. While picking them up the owner offered up a Pioneer SX-990....which is cosmetically wonderful. However he informed me he quit using it because "one time when I hooked up four speakers to it... it started burning". Now I don't see anything charred or discolored, so I assume he meant -smelled- something burning. A long shot most likely, but has anyone here at AK had a SX-990 or similar Pioneer that exhibited that problem, and if so what was the root cause ?

 

[MisterFishey]

Got a set of freebie Utah speakers today. While picking them up the owner offered up a Pioneer SX-990....which is cosmetically wonderful. However he informed me he quit using it because "one time when I hooked up four speakers to it... it started burning". Now I don't see anything charred or discolored, so I assume he meant -smelled- something burning. A long shot most likely, but has anyone here at AK had a SX-990 or similar Pioneer that exhibited that problem, and if so what was the root cause ?

I have an SX-990, but I've never hooked 4 speakers up to it. Most likely, the amperage dipped low, and started to cook the transistors. I would take off the cage on the amp board and see if the transistors are intact, along with everything else on the board. If everything looks fine, I would test it with 2 speakers.

It's a very fine unit, I would recommend keeping it. Recapping is super easy, too. :yes:

 

[Ohighway]

I have an SX-990, but I've never hooked 4 speakers up to it. Most likely, the amperage dipped low, and started to cook the transistors. I would take off the cage on the amp board and see if the transistors are intact, along with everything else on the board. If everything looks fine, I would test it with 2 speakers.

It's a very fine unit, I would recommend keeping it. Recapping is super easy, too. :yes:

Thanks for that quick answer. I'm a bit of a novice on some things so maybe you could walk me through that explanation a bit more.... amperage dipping low? Let me know.

I might open it up this weekend. It's certainly a pretty unit, doesn't look to have been obviously abused.

Your location. Fallston..... as in Maryland ??

 

[toxcrusadr]

What MisterFishey probably meant was that the impedance of the speakers dropped low (i.e. a lot of bass, for example), which is compounded by putting 2 pairs in parallel on the outputs. Too much current was drawn from the outputs causing them to overheat. Very common way for a receiver to die. I would follow his advice on testing it though, it may be fine.

 

[MisterFishey]

Thanks for that quick answer. I'm a bit of a novice on some things so maybe you could walk me through that explanation a bit more.... amperage dipping low? Let me know.

I might open it up this weekend. It's certainly a pretty unit, doesn't look to have been obviously abused.

Your location. Fallston..... as in Maryland ??

Well, you're fine now, the amperage is the resistance of the speakers. If he hooked up four 4 ohm speakers (or maybe even a pair of 8 ohm and a pair of 2 ohm), the resistance in the circuit would drop low, causing the transistors to heat up, which can in some cases fry them. For example, shorted speaker leads make the circuit have a resistance of 0 ohms, which almost always results in damage to transistors if not caught immediately. However, what's done is done, so you don't need to worry. You should be fine testing speakers with it, but with all tests, use some junk speakers just in case.

And yep, that's Fallston, as in Maryland. I see you live down to the Southwest!

 

[Ohighway]

And yep, that's Fallston, as in Maryland. I see you live down to the Southwest!

Or from a different perspective, North of DC...(thank God)

toxcrusadr I see you live in Missouri. Where abouts? I'm married to a Maryland Heights ( St. Louis suburb) native.