Real Repair cases . Different audio brands. Interesting problems. Real troubleshooting and substitution . Component level repair. provolab.com
01/18/2026. Case 3674490. Marantz 1040 amplifier. No left channel.
Missing sound in left channel. After diagnostic and troubleshooting found bad transistor LOCATION HE01 2SC1328 in preamplifier section. Basic test in circuit base-emitter, base -collector shows transistor is good.Under voltage completely different picture . For replacement used 2SC1845.
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 .
