Marantz PM4200 Amplifier Repair

Fault
Cracking sound on all input channels very low Audio output.

Audio signal tracer used to check the output from the input selections ICs
IC21 & IC22 LC7812, signal cracking.

Plus and 15.2 Volt supply rails checked no issue found.

Both ICs replaced fixing the issue.

Boards inspected or Dry joints non found, Bias checked no adjustment required.

User controls and switches cleaned with De-Oxit

Amplifier fully tested working correctly.

• #science_technology
• #marantz_audio
• #marantz_pm4200
• #amplifier_repair
• #amplifier_servicing