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Plate amp expert needed. SW-112


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I have a pair of Klipsch SW-112 subs,  and one started blowing fuses upon plugging in.   I did some digging around and found what looks like a blown ceramic or tantalum cap.  It has some kind of green shrink wrap over it,  so I don't know the capacity or size in order to replace it.  Can anyone figure it out from these images?  The label on the circuit board says TH3,  and there is a TH4 elsewhere on the board slightly larger, and again wrapped with some kind of shrink wrap so I cannot see any color codes or specifications on the component.


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UPDATE:  It does appear to be a varistor or an inrush limiter.  I was able to get it unsoldered from the board and can read SCK, 104,  947. It was very faint,  and part of the markings were damaged with the meltdown. I did some digging around and found that these are sized by diameter,  and mine is about 13mm.   I think I also learned that the 104 means 10 ohm nominal resistance and rated for 4 amps. That makes sense with the protective fuse rated at 3.15 A (weird size, but it is on both the fuse and the holder)  I don't know about the 947, I couldn't find any reference to that.   So if I find any 250 volt,  10 ohm, 4 amp (or greater,  looks like 5 and 6 are available) varistor I should be good to go, or are there other critical specifications?  I see that there is a secondary ohm spec for once you have reached the breakdown voltage, but it is like 250 milliohms, and different tolerance ratings.  It seems these are designed to be sacrificial to protect the rest of the components,  so I am feeling better about my chances of reviving the sub.  I also figured out that the lead spacing was either 7 or 7.5 mm,  and appears to be 0.8mm diameter,  (some higher rated leads are 1.0mm diameter)  Now I just need to find a source that will let me buy just one or two (in case I somehow screw up the first one)   Most of the websites I found while researching want to sell in batches of 50 or more.



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8 hours ago, ngen33r said:

The 104 is an Inrush Limiter



If that is blown 99.999% of the time your fets are toast too as well as some other passives.

I agree. You will probably go down a deep rabbit hole trying to fix the problem. I hope I am wrong but not my experience. Cheaper to just install another D amplifier board inside your old plate. Plenty available on Ebay and other sources. Mouser and Digikey are your sources for parts in the USA. Shipping is expensive for just a few parts though. 

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  • 11 months later...



Im using sub SW-112 broken. I found 2 transistors damage but cannot know what they are as photo attached. Please advise me the name of those transistors for replacement.


Thanks in advance!spacer.png

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