Horizontal Output Transistor (2SC3486) Notes

This horizontal output transformer is used across all four of the multisync NEC JC-140X models. I've had to deal with several ones which are dead, so I wanted to include some notes about how to tell if yours is dead.

A "probably good" 2SC3486 will have the following measurements from a multimeter in resistance mode:

• 340-370K with red probe on base and black probe on emitter
• "OL" out-of-range with red probe on emitter and black probe on collector. If you get a reading of 50M or less resistance, the internal diode is bad, regardless of what diode check shows you. This was consistent across all 4 dead 2SC3486's I've replaced.

A "probably good" 2SC3486 will have the following measurements from a multimeter in diode-check mode:

• beep/good with black probe on collector, red probe on base
• beep/good with black probe on emitter, red probe on base.
• all other combinations of the legs should not show any voltage reading or good beeps on the multimeter.

Be careful to make sure the paper guard behind the 2SC3486 remains in place when replacing one. If the back plate of the chip makes direct metal to metal contact with the heat sink its mounted to, it will arc and kill the chip when powered.