K2475?

W

Walter Harley

Guest
I'm trying to repair a fried switching power supply (it's for a satellite
downlink receiver at a radio station). The supply appears to produce +15V
and +5V at unknown current levels. (Curiously, it does not appear to
produce -15V.) I have three component-related questions that maybe y'all
can help with:

First, there are two components I'm trying to identify. They are in a
TO-220 case. They have a logo that looks like two diodes back to back
(cathode in the middle), and are marked "0984" (probably a date code?) and
"K2475". Anybody know what these might be? They are not heat-sinked.

Second, each of those same two components was encased in a little rubber
"boot." The rubber is some sort of soft, beige material; feels a bit slick,
like surgical tubing, but it's opaque. It's about 1/16" thick. The rubber
is pretty crumbly, and both boots fell apart trying to get them off. The
TO-220 cases themselves are completely plastic, no exposed metal, so I don't
think they need to be insulated further; the boots are not an extremely
tight fit; what the heck *are* these things? And where can I find
replacements?

Third, there are what look like five relatively large (1206?) surface-mount
resistors, each marked 20R, all in parallel with each other. Each one is
obviously blown up. Am I right that these are probably just what they seem,
that is, 20 ohm resistors? (There are no others like them on the board, so
I can't compare with a working one.) And that they're just in parallel in
order to distribute the power? Is this a common technique for
surface-mount?

Thanks for any help!

-walter
 
See answers below.

--------------------------------------
Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

"Walter Harley" <walterh@cafewalterNOSPAM.com> wrote in message
news:bua0sd$sk2$0@216.39.172.65...
I'm trying to repair a fried switching power supply (it's for a satellite
downlink receiver at a radio station). The supply appears to produce +15V
and +5V at unknown current levels. (Curiously, it does not appear to
produce -15V.) I have three component-related questions that maybe y'all
can help with:

First, there are two components I'm trying to identify. They are in a
TO-220 case. They have a logo that looks like two diodes back to back
(cathode in the middle), and are marked "0984" (probably a date code?) and
"K2475". Anybody know what these might be? They are not heat-sinked.
Oooh, that logo is frustrating, because I kinda remember it -- is it the old
International Rectifier logo? I have no idea what the chip number means,
but TO-220 thingies in a switching power supply are probably power
transistors, likely MOSFETS, particularly if they are connected to rectified
power, a big transformer, and thing that looks like a control chip (or a
little transformer).

Second, each of those same two components was encased in a little rubber
"boot." The rubber is some sort of soft, beige material; feels a bit
slick,
like surgical tubing, but it's opaque. It's about 1/16" thick. The
rubber
is pretty crumbly, and both boots fell apart trying to get them off. The
TO-220 cases themselves are completely plastic, no exposed metal, so I
don't
think they need to be insulated further; the boots are not an extremely
tight fit; what the heck *are* these things? And where can I find
replacements?
Some perverted form of sil-pad?

Third, there are what look like five relatively large (1206?)
surface-mount
resistors, each marked 20R, all in parallel with each other. Each one is
obviously blown up. Am I right that these are probably just what they
seem,
that is, 20 ohm resistors? (There are no others like them on the board,
so
I can't compare with a working one.) And that they're just in parallel in
order to distribute the power? Is this a common technique for
surface-mount?
Paralleling surface mount componants for power dissipation is not uncommon;
high-power surface mount resistors can be expensive and rare. If you're
assembling your power supplies in Taiwan and if the absolute smallest size
isn't your goal you may want to go brute force with available componants.

Thanks for any help!

-walter
 
Here's the link to the info on your FET- 2SK2475
with japanese parts the 2S is assumed, as a C1302 is actually a 2SC1302...
http://semi.shindengen.co.jp/en/2sk2475.pdf

The round tube is a tube of the same material as Sil-pad, it is used as a
heat sink, which is funny because it just doesn't increase heat dissipation
much when used like that. If I were you and had enough room, I'd find a way
to mount some small aluminum heatsinks to those FET's

Your resistors are probably 20 ohm, and most likely are paralelled to
dissipate more power. The manufacturer may have bought the surface mounts in
enough quantity to make using a lot of them cheaper than using 1 large power
resistor.


--
Jammy Harbin
J & J Electronics, Inc
227 S. 4Th St.
Selmer, TN 38375
731-645-3311

"Walter Harley" <walterh@cafewalterNOSPAM.com> wrote in message
news:bua0sd$sk2$0@216.39.172.65...
I'm trying to repair a fried switching power supply (it's for a satellite
downlink receiver at a radio station). The supply appears to produce +15V
and +5V at unknown current levels. (Curiously, it does not appear to
produce -15V.) I have three component-related questions that maybe y'all
can help with:

First, there are two components I'm trying to identify. They are in a
TO-220 case. They have a logo that looks like two diodes back to back
(cathode in the middle), and are marked "0984" (probably a date code?) and
"K2475". Anybody know what these might be? They are not heat-sinked.

Second, each of those same two components was encased in a little rubber
"boot." The rubber is some sort of soft, beige material; feels a bit
slick,
like surgical tubing, but it's opaque. It's about 1/16" thick. The
rubber
is pretty crumbly, and both boots fell apart trying to get them off. The
TO-220 cases themselves are completely plastic, no exposed metal, so I
don't
think they need to be insulated further; the boots are not an extremely
tight fit; what the heck *are* these things? And where can I find
replacements?

Third, there are what look like five relatively large (1206?)
surface-mount
resistors, each marked 20R, all in parallel with each other. Each one is
obviously blown up. Am I right that these are probably just what they
seem,
that is, 20 ohm resistors? (There are no others like them on the board,
so
I can't compare with a working one.) And that they're just in parallel in
order to distribute the power? Is this a common technique for
surface-mount?

Thanks for any help!

-walter
 
"ampdoc" <ampdoc@NOSPAMPLEASEhotmail.com> wrote in message
news:bH1Ob.8136$0t4.2597@bignews5.bellsouth.net...
Here's the link to the info on your FET- 2SK2475
with japanese parts the 2S is assumed, as a C1302 is actually a 2SC1302...
http://semi.shindengen.co.jp/en/2sk2475.pdf
Thanks! After I get told that 30 or 40 more times, maybe it'll sink in. In
the meanwhile, thanks.


The round tube is a tube of the same material as Sil-pad, it is used as a
heat sink, which is funny because it just doesn't increase heat
dissipation
much when used like that. If I were you and had enough room, I'd find a
way
to mount some small aluminum heatsinks to those FET's
That's what I'm thinking too. They're actually mounted right next to the
chassis, so it would be very easy for me to just drill some holes in the
chassis and mount them. Since they're isolated already it should be fine.

I appreciate the help!
 
"Walter Harley" <walterh@cafewalterNOSPAM.com> wrote in message
news:bua0sd$sk2$0@216.39.172.65...
I'm trying to repair a fried switching power supply (it's for a satellite
downlink receiver at a radio station). The supply appears to produce +15V
and +5V at unknown current levels. (Curiously, it does not appear to
produce -15V.) I have three component-related questions that maybe y'all
can help with:

First, there are two components I'm trying to identify. They are in a
TO-220 case. They have a logo that looks like two diodes back to back
(cathode in the middle), and are marked "0984" (probably a date code?) and
"K2475". Anybody know what these might be? They are not heat-sinked.

Second, each of those same two components was encased in a little rubber
"boot." The rubber is some sort of soft, beige material; feels a bit
slick,
like surgical tubing, but it's opaque. It's about 1/16" thick. The
rubber
is pretty crumbly, and both boots fell apart trying to get them off. The
TO-220 cases themselves are completely plastic, no exposed metal, so I
don't
think they need to be insulated further; the boots are not an extremely
tight fit; what the heck *are* these things? And where can I find
replacements?

Third, there are what look like five relatively large (1206?)
surface-mount
resistors, each marked 20R, all in parallel with each other. Each one is
obviously blown up. Am I right that these are probably just what they
seem,
that is, 20 ohm resistors? (There are no others like them on the board,
so
I can't compare with a working one.) And that they're just in parallel in
order to distribute the power? Is this a common technique for
surface-mount?

Thanks for any help!

-walter

Probabally a 2SK2475 ie 500V MOSFET, try a Google search for details.
 

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