CASE # 876500 . 12/03.2025 . MCINTOSH MA6100. No sound from right channel.
Customer shorted speaker wires and lost right channel.
After troubleshooting found 2 fuses for right channel are blown. Output transistors dead too. Rest of parts tested ok. This model use hard to find 132-128 Motorola NPN transistors . MJ15022 transistors are perfect substitute. Installed, tested , no need any adjustments.
CASE # 453621 . 12/03/2025 . SANSUI TU-717 TUNER. No FM. AM band is ok.
Interesting case. All voltages in FM section is normal . After touching pin 1 on LA1222 we have sound respond in FM IF line, meaning something not working before LA1222 IF amplifier . After shorting legs on CFC01 filter ( pin 1 and 3 ). FM band starts working. Filter CF01 is bad. In case if you don,t have such unusual part you can use any non electrolytic small capacitor value 10pF -5000 pF, voltage no matter, between pins 1 and 3 on CF01 filter .
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.
