This component carries the markings SMS5408 0932 is busted! It is part of a 1000W psu of a flagship subwoofer of a (very) respectable brand, and I can't find any datasheet at all for it!

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I assume it is a MOSFET because of the G,D and S markings on PCB. Only thing I could find for the SMS was this company:


that seems to provide asic services, doesn't seem to manufacture components. Also couldn't find any reference for 5408 except diodes.

Usual websites like alldatasheet, datasheetcatalog, etc didn't bring anything up. Contacting the manufacturer is no good, they've sent me another unit so no one would have to worry about repairing anything. But I really won't let this off because I can't find a replacing mosfet!! ;)

New image (PCB backside):

PCB backside

  • \$\begingroup\$ Looks like the S pad is torn apart. Are you sure the board would accept a new transistor? \$\endgroup\$ – EasyOhm Jan 2 '15 at 5:44
  • \$\begingroup\$ Did you look at the replacement unit? It might have more useful markings. \$\endgroup\$ – Spehro Pefhany Jan 2 '15 at 6:06
  • \$\begingroup\$ I wasn't able to track that part down, either. But you may take into consideration that it may be an IGBT. This depends on currents and voltages used in the circuitry. Do you have any knowledge about these values? \$\endgroup\$ – Ariser - reinstate Monica Jan 2 '15 at 12:20
  • \$\begingroup\$ Hrm, this is a tough one; 5408 appears one of the most overused ids/numbers in electronics history: there's 2SC5408 (a NEC NPN transistor), 2N5408, 1N5408 none of which make sense in this application... \$\endgroup\$ – Fizz Jan 2 '15 at 13:44
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    \$\begingroup\$ Best guess I could come up with would be possibly some un-listed device from this Chinese company: sino-mostech.com/ShowProducts.asp?id=49 \$\endgroup\$ – justing Jan 2 '15 at 20:18

One possibility for a 5408 is the military grade of the old 7408 TTL IC, but that's normally in a 14-pin DIP package instead of having only 3 pins.

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    \$\begingroup\$ I'm not sure how a 14-pin DIP would be useful for replacing a 3 pin component... \$\endgroup\$ – Null Jan 14 '16 at 5:14
  • \$\begingroup\$ Well , the first main issue is to know what is the SMS 5408 and its specs - I still don't know these information, but I still have the PSU hoping to fix it someday... So why would I replace it for a 7408, even if it would fit, if I don't know what it is for sure? \$\endgroup\$ – tfm Jan 20 '16 at 1:00
  • \$\begingroup\$ The 5408 I was referring to is a TTL chip containing four AND gates. Very unlikely to be used in a PSU. \$\endgroup\$ – user6030 Jan 22 '16 at 4:33

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