identifying a semiconductor component

Papa_Bear

I have a 3 terminal device that i am trying to identify the specs of so that i can replace it . It looks like a voltage regulator to me. All 3 pins seem to be shorted out (v. low resistance) and it has a n.o on the case 01 k24645.47.

Judging from the circuit I took it from (high voltage side of a power supply board for a comag sl55 sat box) I would guess it's function is regulation. It has a hole for fixing to a large heatsink (which produced alot of heat so probably large current) but the entire case is plastic and does not have the metal plate on the back which (usually) rests against the heatsink.

I tried googling the part no. but all i can see is that it is possibly an N-channel MOSFET. That is to say all i can find in a search is results showing k2645 without the rest of the no. and so cannot find any specifics.

Got any ideas?

Cheers

Johnboy1951

It might be helpful to trace the tracks and connections of associated components on the board and draw that part of the circuit diagram .......

Papa_Bear

That would be kind of hard to do and it probably wouldn't mean a whole lot to me. Think i'll just try taking a rough guess at a suitable regulator and keep well back:eek:

Chet T16

Papa_Bear wrote: »

That would be kind of hard to do and it probably wouldn't mean a whole lot to me. Think i'll just try taking a rough guess at a suitable regulator and keep well back:eek:

You don't even know if its a regulator!

jason2010

Hi,
Does it have a metal top with a place for a screw to screw it down onto the board ?

Johnboy1951

Papa_Bear wrote: »

That would be kind of hard to do and it probably wouldn't mean a whole lot to me. Think i'll just try taking a rough guess at a suitable regulator and keep well back:eek:

Others might be able to make a more informed guess at the component if you posted the diagram .... but up to you

Papa_Bear

I'm taking a guess that it's a regulator. No it doesn't have a metal back for screwing down but it does have the hole to fix to a heatsink but its all plastic case.

gctest50

Like any of these ?

Chet T16

Papa_Bear wrote: »

I'm taking a guess that it's a regulator. No it doesn't have a metal back for screwing down but it does have the hole to fix to a heatsink but its all plastic case.

Get some pics up we can have a look at

Chet T16

Is it the same as this pic?

Papa_Bear

Chet that's the very one alright, screwed to the heatsink at the bottom right of the picture.

Since you have the picture up I was wondering if you knew the value of the resistor under C1 as it is blown and I cant determin its value (plus im no good with colours anyway).

What I find strange about this circuit is that there is a bigger transformer than the ones shown, over on the other side of the heatsink but this is after the bridge rectifier so how can a transformer work ton DC current - is it being used as a large inductor?

Many thanks for your help.

Papa_Bear

gctest50,

I don't see it in that pic but possibly the one on the left middle row - i cant be sure.

Here's a photo of it anyway.

gctest50

Papa_Bear wrote: »

What I find strange about this circuit is that there is a bigger transformer than the ones shown, over on the other side of the heatsink but this is after the bridge rectifier so how can a transformer work ton DC current - is it being used as a large inductor?

They usually go a bit like this :

[230v AC] -----> DC ----> High Frequency ----> transformer ----> 

rect/reg/feedback-------> out

ZENER

By the looks of it the component you're trying to identify is tasked with chopping up the rectified and smoothed mains voltage - about 380VDC usually. Could be a mosfet or bi-polar transistor.

The resistor in the picture above is 650 ohms 5% tolerance, by it's size I'd guess at a 1watt type.

Ken

whizbang

http://pdf.datasheetcatalog.com/datasheet/fuji/2SK2645.pdf

Probably anything at all from an old SMPS will do the job as a replacement, But its quite likely there are a ton of other components blown also.

I think you would be better off replacing the whole thing.