Tested output transistors and found 3 transistors 2sb554 is out and 3 resistors and 2 transistors on driver board are dead too. Replacement parts in driver board was easy to find and no problem. But 2SB554 was a big pain. I have tried 2 different sellers from Ebay with negative experience. They all selling junk copy of original Toshiba transistors. They selling transistors 2SB554 with fresh printed red numbers on them. They look new and freshly made .
They are junk !!!!!
After negative experience i used original 2N6609 FROM MOTOROLA WITH GOOD RESULTS. I replaced all 4 transistors 2sb554 with 2N6609. Unit tested few days with real sound , temperature – ok, dc offset ok , BIAS -OK, frequency respond perfect. They have same NTE numbers and pinout and working good. NPN transistors still original and were not changed.
