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Marantz 4270 output transistors. Best cross
Marantz 4270 output transistors. Best cross
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Old 25th February 2008, 03:51 AM   #1
The Donk! is offline The Donk!  United States
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Default Marantz 4270 output transistors. Best cross

I'm trying to choose the best subs for 2sc897s. These go in a marantz 4270 I'm tryin to restore. It only has two bad, or really leaky transistors in it now, but I want to replace them all. So everything is even, and what not.


I have two places to buy parts from locally. MCM electronics and parts express.

I've read that MJ15003 are a good cross for the c897s. But MCM's computer is telling me that 2sd424's are a cross for the c879s.

Now, I'd almost prefer the MJ15003, but I hear about fake onsemi's all the time.

Will the 2sd424s work ok. It all seems to work out on paper, but you never know.

Mouser carries the MJ15003, but that a few days shipping.

Who wants to wait that amount of time, and dammit! What if they're fake?

I;m hoping the 2sd424s will work.

any thoughts would be super.
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Old 25th February 2008, 08:40 AM   #2
jaycee is offline jaycee  United Kingdom
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Location: Norwich, UK
2SD424 is just as obsolete and difficult to find as the original is.

If you buy your MJ15003 from Mouser, you won't get fakes as they will be dealing with On Semiconductor directly. It is mainly smaller retailers that deal with wholesalers and middlemen that are likely to have fakes.
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Old 25th February 2008, 10:42 AM   #3
east electronics is offline east electronics  Greece
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Location: Athens GREECE
Default once .....

had to replace some of them too .....

from listening impressions i had the chance to both listen mj15003and the very nice 2sa1302+2sc3281

BUT !!!!!!!
the 2sa+2sc difrent fit of course sounded much warmer and more musical than on semi ..... also tryied diferent bias between 100ma-200 ma .....

finally i stayed with the 2sa and about of 100ma bias ....

the only thing is that i have plenty of them original .......sorry to say i will not sale not even one ......i prefer to sel my hand instead

best regards sakis
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Old 25th February 2008, 10:48 AM   #4
Burnedfingers is offline Burnedfingers  United States
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Join Date: Nov 2002
I have never received any fakes from Mouser.

Don't go overboard with the bias... it is best to use a distortion analyzer in setting the bias instead of the "ear" method. The ear method cannot be relied on as a proven method. Set to factory specifications and check with an analyzer. This will guarantee much longer output life than the "ear" method.
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Old 25th February 2008, 10:06 PM   #5
The Donk! is offline The Donk!  United States
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Join Date: Feb 2008
I picked up NOS toshiba 2sd424s from MCM today.

Everything is goin well. The left channel now works. The right worked, but I'm redoing it as well.

I also replaced all the capacitors on the amplifier boards, and think I will re-cap the preamp next.

So now, everything is good. I just need the alignment procedures to do all this.

If anyone can tell me how to set the bias current for this amp, It would be great.

It's basically a 4 channel amp, that bridges two channels per side, to get just two channels in stereo mode.

So, I see three variables on the top of the amp boards.

Any idea which ones do what?
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