The defendant has appealed from his conviction on an indictment charging assault and battery by means of a dangerous weapon. He argues only his assignment of error to the effect that the judge's charge on self-defense was inadequate and did not "inform the jury that the Commonwealth
had the burden to prove the absence of self-defense beyond a reasonable doubt." There was no dispute that the defendant and the victim engaged in a physical altercation, the only issues before the jury being whether the defendant was acting in self-defense and whether the stab wounds on the victim were from a knife wielded by the defendant or someone else at an earlier time. The defendant denied using a knife. No knife was found by police officers who arrived at the scene during the altercation. The judge charged the jury on the Commonwealth's burden of proof and on self-defense. No exception was taken to the charge, and no request of any kind was made to the judge at the conclusion of the charge. The charge was given two months after the Supreme Judicial Court had issued its opinion in Commonwealth v. Rodriguez, 370 Mass. 684 (1976). If the defendnat considered that a charge specifically stating that the Commonwealth had the burden to show the absence of self-defense beyond a reasonable doubt was desirable, he should have asked the judge to give such a charge. An assignment of error under G. L. c. 278, Section 33D, not based on an exception brings nothing to this court for review. Commonwealth v. Miskel, 364 Mass. 783 , 792 (1974). Having read the charge in its entirety, we do not consider this an appropriate case in which to "employ the rarely used power referred to in Commonwealth v. Conroy, 333 Mass. 751 , 756-757 ." Commonwealth v. Freeman, 352 Mass. 556 , 564 (1967). Commonwealth v. Peters, 372 Mass. 319 , 324 (1977).