Can i replace 2SB755 / 2SD845 Toshibas for 2SA1494 / 2SC3858 Sanken ?

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Thank you Sakis !!!

I will replace them in both channels...and i have another problem, because more transistors are blown up ( drivers ) 2SA1184 / 2SC2824 and the pair 2SA915 / 2SC1940, i still have to find good replacements for this ones...

I'm sure you can replace 2SA1184 / 2SC2824 with 2SA1837 / 2SC4793 and
2SA915 / 2SC1940 with BC639 / BC640. The BC's have slightly lower voltage rating, but the amplifier is a 70 W, so I'm guessing an 80 V transistor should do fine. Measure the supply rail-to-rail. My guess would be around 72 V. I'm also of the impression the full supply voltage can never be put across these transistors.

Measure; don't take my word for it.
BC639 640 is a choice that will only cause trouble ...Vbe data will change and the all thing will be messed up ....very marginal from any aspect ...

Vbe on the BCs is very slightly less than on the 2SA915 / 2SC1940. I would guess they wouldn't be running at more than 5 mA. At 5 mA, the old transistors will have a Vbe about 0.67 V vs the BCs at 0.62 V. I personally don't think it will be cause for concern. I may be wrong, but in my experience, this size difference (up to 10%) is within device tolerance anyway, and no design should be that tight.

Below 5 mA, the difference is even more negligible.
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Like Sakis, I would never let a BC transistor touch a Japanese amplifier. Not only will it probably not work well, but it also feels a bit heretic.

I think KSC2383 and KSA1013 would probably work well in place of the KSC1940 and 2SA915. Cheap and widely available. Good parts.
Maybe i could use 2SA1306/2SC3298 for drivers and 2SA949/2SC2229 for predrivers because this ones i have ...they are a bit more beefy than the originals, but probably will do well...shall i give it a try ? As said here, i will never mix BCs with 2Ss...say japaneese with european transistors...

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hahahahhaha .... you could but i dont think that 1306-3298 that you have are originals unless you pulled them out of a working amp ...Sorry to say that i have them also original ( the green ones for the PNP ) in the same prize ...each ...

I am not trying to sell here ... but YES i like to brag a bit about my stock ...


Well Sakis, i have this board to pull this transistors and use them in my amp, but maybe i can find some new originals still around here in my country...


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Those and many more days we repair about 1000 audio devices per year mostly amplifiers
before i got this stock most of the times we had to modify amplifiers similar way like you are trying and go as close is possible but we consumed time and we had to long run and evaluate changes from any aspect like stability oscillations and /or others ...

Now i am offering my customers original replacements at a very expensive cost but they get to keep amplifier very very original in case they like to ...So i make money with this and also i save time since the original you only have to solder them inside measure offset and bias and you are sure and done within minutes ...

I have about 30pcs of 2SK150 another 20 of 2SK34 ( very rare ) and about of 100 pcs from 2SC 1000 or 2sc1313 all of them extremely rear to get in original condition ...

I think in the near feature i am going to have so much fun with those and money also .

I showed the parts in my every day semiconductor supplier here in Greece and the guy actually started to cry !!!!! ( i offered also to sell to him at 10 euro a piece ):p:p:p:p
Well, today i finished the repair of my Onkyo A-45, and maybe it could be usefull for someone with same problem. I replaced the outputs 2SB755/2SD845 for 2SA1301/2SC3280...the drivers 2SA1184/2SC2824 for 2SA1535A/2SC3944A...the pre-drivers 2SA915/2SC1940 for 2SA1123/2SC2631 and replaced the DC servo controller 4558DX for NE5532, and it works perfect, so i am going to do the same in the other channel :)
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