fixing my friend's amp....

[benmanf]

hi everybody!
wasnt here for long!

my friend gave me a broken mosfet amp...to see what's the problem...
well...some of the transistors were blown up totally
i really know nothing about mosfets...

the amp is 100Wx2 (stereo)...both sides are dead...
the blown trans. were k1420 ( 2sk1420 ?? )
or... at least 2 of the 4...
the other two were blown up to pieces...hehehe....I could'nt recognize them.... 😕
i think they were k1420 too....

where can i get it on the internet?
i live in israel so i need an international shiping too...

and maybe i can any other transistors instead of the k1420 ?

thanks!

 

[mrshow4u]

....maybe these guys will have??
http://www.bmm-electronics.com/Product.asp?Product_ID=2826

 

[benmanf]

wow, crazy shipment prices!
70 dollars for UPS
30 dollars for standard mail

😛

but thank you!

maybe any other sites?

 

[derguteton]

2SK1420

You can have it (and several others) from me, from Germany.

2 Euro/ Piece, 8 Euro packing and shipping to Israel

Greetings from Berlin, Michael

 

[mrshow4u]

....Holy s***, I didn't notice their shipping prices!! Maybe they are shipping a whole wafer fab for that price? Very nice of Derguteton to help with this. I get the feeling these particular MOSFET's might be out of production. That was a cool picture of the blowup. Is this thing a complementary design? Are ther 2SJ's in there too?

 

[benmanf]

hey, i'd like to have it from you, derguteton!
thank you!
how can i contact you?

mrshow, i dont know, didnt find any 2sj's there...

btw, the amp is a car amp- "JENSEN ALX2000" or something like that 😀


hmm...i really hope that these transistors are the only problem...

what do you think?
everything on the board looks good...not black or something like that...

what do you think i need to test first?

 

[mrshow4u]

.....Hmmmmmm, the explosions seemed to be in the vicinity of what looks like the power supply. That would make sense that they'd all be N-Channel MOSFETS. ....although, lot's of car amps don't use complementary outputs (K's and J's). These switcher supplies don't really reliably start with slowly feeding them a ascending DC voltage. I would at least check your output devices (The one's that don't look blown up under the heat spreaders.) and rectifiers. If the output transistors (or rectifiers) are shorted, the power supply' new devices might re-fry trying to dump into a still blown power amp section. If the output transistors are BJT's, you can lift the middle pin on all of the outputs (Collector), replace, your exploded components and fire it up and see if there is still a problem. If the power amp's output devices are MOSFET's, you might have to consult a datasheet and lift the Drains. Since you're paying for shipping and handling, you might consider getting extras

 

[benmanf]

ok.......now i get it!
now i know what to check...

btw the output devices are KTD718(NPN) and KTB688(PNP)
tomorrow ill check it....now its 23:55 in israel 😀
if these transistors are ok, probably everything is ok...
but i will check all the transistors there.....

thank you!

and derguteton:
i still want the transistors!
how can i contact you?

 

[benmanf]

ohh...and what is that thing in the picture?
cant find datasheets for it....

if you dont understand what is writen there:
C25 53
-|<-->|- (two diodes)
02N

 

[rodolfo]

is a amp jensen?????

ok

this ( 2sk1420 ?? ) >>>>>>>>>>>irfz44n is ok & are 4 pz. all same tipe
this c2553 02n>>>>>>>>>>>>>>>>> stpr1620ct or similar(200v_16A )
sorry for my poor englis

 

[mrshow4u]

Yes, that thing in the picture you'll definitely want to check those. That is a a double diode with the anodes tied together. If those are shorted, you'll definitely want to change those before turning things on again. Make sure you replace those with equivilent or better. They'll be Shottky diodes. They're unique in that they are very fast. This is required because the power supply uses a high oscillation frequency. Anything with that double diode insignia will be important to check!!!

 

[benmanf]

this c2553 02n>>>>>>>>>>>>>>>>> stpr1620ct or similar(200v_16A )

thank you rodolfo!
the part that i quoted is what i need but i need the oposite of it too...
i mean that the diodes are on the oposite side...
what is the name of that part?

and are you sure that irfz44n can replace 2sk1420?
if so, thanks a lot!


and mrshow4u
thanks! ill check it too....
i think i'll go and check it now!

 

[benmanf]

OK....I have checked all the output transistors and the rectifier diodes...everything looks good, no short circuits......

anything else to check?

and..... can i use anything else instead of 2sk1420 or irfz44n ?
i want to order some samples from a site like OnSemi or something...

so what are the characteristics of that transistor?
so i'll check in sites that give samples.... 😀

for example: Fairchild gives free shipping....
maybe something from them?

 

[mrshow4u]

....click on the hyperlink of this page: <http://www.datasheetcatalog.com/datasheets_pdf/2/S/K/1/2SK1420.shtml>