McIntosh MC112 No Stereo or Stereo Light
ฝัง
- เผยแพร่เมื่อ 7 ก.พ. 2025
- This is a McIntosh MX112 Tuner/Preamplifier that had no FM stereo and subsequently no stereo light. I found the 16-volt regulated supply down to a little over 14V. Replacing the 16V Zener at D201 in the power supply brought the voltage back up to 16. The 16 volt was now good at the collector of Q101 but the base and emitter voltages were low. There is a 1.5M pullup resistor at R101 on the MPX board that was a bit out of range. Not enough that I would normally think it would make a difference but I replaced it anyway. This brought back the stereo light flashing with the signal. A strong bass note would cause the light to flash for a fraction of a second. The base and emitter voltages came up a bit with changing the emitter resistor so that led me to the transistor itself. Although it checked good with no discernable leakage, replacing the transistor restored normal operation. The transistor was a 132-057 which subs to a BC168C.