K1257 transistor datasheet needed.

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J

jude

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Joined 2002
Hey all.. I just searched for the fryed transisters on digikey and can't find any... the number is K1257.. My data manuals are nowhere to be found right now, so I was wondering if someone could give me a replacement number, or some info on these transisters...

thankyou.
Jude
 
J

jude

Member
Joined 2002
whell.. it is in the power supply stage of my kenwood amp that is screwed.. It says K1257 then (m)30 then Japan.. that is it... there are two of them that I can't even read because they are too badly damaged, and two that are kind of allright.. on the pc board it says K1257..

the case is one of those little boxes with the tab on top and the tab is a connection.. forget what they call this type of case... It is a usual MOSFET case tho...

I am looking for replacements for these so I can see if I can get this amp fired back up..

Thankyou for your help...

Jude
 
J

jude

Member
Joined 2002
oohh.. 6 bucks each... that was a little bit more than I wanted to spend... how exactally do I check capacitors and the other things like that.. If I spend 6 bucks a FET, I want to make sure they aren't going to go up in smoke..

thanx again..
Jude
 
tvi

tvi

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Joined 2001
With big electrolytic capacitors I usually charge them up with my multimeter on Continuity/Diode test (about 3V), then swithh to Volts dc and watch them discharge slowly through the Multimeter.

The voltage should drop fairly smoothly, slowing down when it gets below about 1V.

Of course you will have to take them out of circuit.

For testing MOSFET see: <a href="http://www.4qd.co.uk/serv/mostest.html">MOSFET testing
</a>

<pre>IRFIZ48V N-ch 60V 39A 43W 0.012R TO220F</Pre>

Regards
James
 
J

jude

Member
Joined 2002
UPDATE...

whell.. I figured out what was happening... I went out today and bought a digital multimeter cauz they were like 23 bucks on sale.. not bad... Brought it home, Popped a battery in it, and started testing my capasitors now that I have ordered the transistors... everything seemed normal.. I realized that I missed a bigger one.. it was a 3900MF 16V one at the corner of the board... I checked it.. the resistance started to climb as it charged... Good good.... then it stopped... I did not receve a reading of 1 (infinite).. BAD CAPACITOR!! I followed the traces to the K1257 with the chunks out of it.. It appeared that it was supposed to allow 12V high amperage to the scource of the MOSFET, then shut off.. the shutting off wasn't happening, so the chunks flew out of the transistor ;).. gotta follow the traces thru the power supply now to check if anything else was damaged... lets hope not...

Whell.. thankyou for your help in finding the right replacement transistors...

Jude
 
peranders

peranders

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Joined 2002
sjostromaudio.com
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Re: UPDATE...

jude said:
I realized that I missed a bigger one.. it was a 3900MF 16V one at the corner of the board... I checked it.. the resistance started to climb as it charged... Good good.... then it stopped... I did not receve a reading of 1 (infinite).. BAD CAPACITOR!!
Click to expand...

The resistance of an electrolythic capacitor can be 100kohm - more than 10 Mohms.

See my post in the end of the thread.

http://www.diyaudio.com/forums/showthread.php?s=&threadid=5125&perpage=15&pagenumber=2
 
J

jude

Member
Joined 2002
yeah.. but usuallyif they charge up with DC current, they can block the current as soon as they are charged.. thats what they are used for aren't they? I think the capacitor is what fryed my MOSFETS.. the resistance was rather low anyway...

Thanks anyway..
Jude
 
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