On 4 Aug, 08:36, KaLe wrote:
Dana Fri, 3 Aug 2007 14:33:57 -0700 na news grupi sci.electronics.repair
osoba pod imenom David Farber je napisala...

According to my 1986 Transistor manual these are the ratings.

* I'm not quite sure how the 2SB649 is only rated at 1 watt while the 2SD669
complement is rated at 20 watts. Also notice that these substitutes have a
lower breakdown voltage than the originals.

Good luck.

Thank you for that information David. About collector power dissipation
different between 2SB649 and the 2SD669; they are talking about two kind
of Pc, one is normal Pc and one is Pc with mark * and notice Tc = 25
degrees C, that Pc with * is 20 W, and Pc without * is 1 W.

Tamb=25C vs Tcase = 25C wont explain that much difference. You dont
use 20w trannies as drivers in a tr amp.

Also your betas are different, 60 may be not enough.


I do not need that high breakdown voltage, 180 Volts is quite enough,
because they will work as predrivers in audio receiver Sansui G8000.
But I am wondering about that big difference between collector current,
2SC2071/2SA939 have only Ic 50mA and 2SB649/2SD669 have 1.5A, how big
difference?!? Is it really good value, did you checked?

Regards!


I wouldnt choose a 20w tr as a driver. It may well work tho.


NT