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Pioneer SX-1280 NEC D746/B706 Output Transistors

zealth1960

zealth1960

New Member
Just got a blown SX-1280
Going to replace Output Transistors NEC D746 and B706
Im finding these hard to find and pricey
Are there any cheaper replacements for these ??????
 
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Not drop in, but... Onsemi MJL39115 and MJL31196, or MJl3281 and MJL1302 would work, except you would have to change mounting (not the same cases, but close enough that it probably would be doable - search sx1980 outputs for some solutions.
Also large Sanken outputs should work with some modification. 2sc2922 and 2sa1916, 2sc3858 and 2sa1494 (Bdent is authorized Sanken distributor.)
 
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Hi Steve
Thanks for the reply
I checked them out but im only seeing 3pinout
Im taking it very slow and have done allot of stereo repairs but
Are all 4pins on the D746/B706 not being used ????
Do I have to tie in on one of the 3pins

Thanks in Advance
Kevin
 
2 pins are duplicate there are only 3 terminals for a bjt.
P42 in the service manual shows the pinout CBEC
 
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rcs16 said:
2 pins are duplicate there are only 3 terminals for a bjt.
P42 in the service manual shows the pinout CBEC
Click to expand...
I was about to say that, I was under the impression that there were common collector terminals...
 
You found the sx-1280 thread where I replaced the outputs with modern packages.

here's another: http://audiokarma.org/forums/index.php?threads/sx-950-and-an-interesting-guy.239265/#post-2872715

863-mjl4302ag pnp TO-264 bce 350V 15/30A 230W 35mhz 50-250hfe $5.62 EW USED IN SX-1980
863-mjl4281ag npn TO-264 bce 350V 15/30A 230W 35mhz 50-250hfe $6.25 EW USED IN SX-1980

Those transistors are in short supply at mouser right now, these are other usable numbers, from my notes:

863-MJL0302AG pnp TO-264 bce 250V 15/30A 150W 30MHZ 75-150hfe obsolete
863-MJL0281AG npn TO-264 bce 250V 15/30A 150W 30MHZ 75-150hfe obsolete
but this is obsolete???
863-NJW0302G pnp TO-3P bce 250v 15a 150w 30mhz 75-150hfe $1.91
863-NJW0281G npn TO-3P bce 250v 15a 150w 30mhz 75-150hfe $2.10


863-MJL1302AG pnp TO-264 bce 250V 15/30A 200W 30mhz 45-150hfe $3.57 ea
863-MJL3281AG npn TO-264 bce 250V 15/30A 200W 30mhz 45-150hfe $3.57 ea

863-njw1302g pnp TO-3P bce 250V 15/30A 200W 30mhz 45-150hfe 2.55
863-njw3281g npn TO-3P bce 250V 15/30A 200W 30mhz 45-150hfe 2.32

I have NOT gone to Mouser to check these numbers.
 
sregor said:
Not drop in, but... Onsemi MJL39115 and MJL31196, or MJl3281 and MJL1302 would work, except you would have to change mounting (not the same cases, but close enough that it probably would be doable - search sx1980 outputs for some solutions.
Click to expand...

FWIW I mentally switched MJL and MJW. The MJL are larger and better choices for power reasons, and edited my post.
 
Old post, but still VERY relevant.
Working on an sx-1280 now.
Sourced the njw1302g/3281g replacements as called out by @markthefixer.
Will post back when I get them installed and the output stage re-biased.
Would like to go with MJ15024/25's as they are proven workhorses, but the retrofit would be much more complex.
Media post shows the working left channel pumping out ~240 watts rms.
Cheers!
IMG_20200105_162001

IMG_20200105_162001

  • Media owner PuckNut
  • Date added
SX-1280
right channel removed for repair
left channel, under load, ~240 watts rms (30.8 vac...
 
MJ15024/25's in to-3 metal cans? how the heck are you going to mount them? stick with what has been proven to work.
 
PuckNut said:
Would like to go with MJ15024/25's as they are proven workhorses, but the retrofit would be much more complex.
Click to expand...
Why? They have nowhere near the transition frequency of the originals and are not a good match for the amplifier design, the 3281/1302 are so much closer to what the original transistors and much easier to fit.
 
PuckNut said:
Would like to go with MJ15024/25's as they are proven workhorses
Click to expand...

THAT would be a mistake. As kevzep points out, they have a Ft (4 MHz) that is slower than the replacements (30 MHZ), and the originals (15 MHz) .
 
Yikes!
Slow down gents.
Replacement parts are in route as stated.
And the to-3 idea shelved as well.
The Motorola's are stocked and gain matched for commercial amp repair....to-3 sockets as well.
Heat sink mods for these guys are not that difficult, except in this case.
Rest assured, this fix is following recommendation. Thank you.
 
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