Malan scholar PM-4 methyl class amplifier machine, is Malan scholar PM series most worth collection of a paragraph methyl class amplifier machine, it soft of timbre, dare and bile machine bi beauty, is high of Jie Xili and is better than bile machine. odd shaped of appearance unique, alone led coquettish, when of top methyl class machine Emperor. sound sweet charming amplifier, real for methyl class machine of model, with has more than 10 years rare maintenance once. Open PM-4 is not difficult to find, on a previous design of amplifier circuit is also very ugly, it was not easy to disassemble for maintenance, compared to today's circuit design, technology has been a leap of progress.quQservice manual download site
quQservice manual download site
quQservice manual download site
quQservice manual download site
Symptom: power worked, right channel sound normal, left channel sound is very weak.quQservice manual download site
Left and right channel separately testing, symptoms, indicating faults within the machine. Oscilloscope signal for open cover, left and right channel inputs of the audio signals to the front panel switch of balance, but wants to continue to be able to look up is somewhat difficult, motor and wiring is relatively complex, are lines everywhere.quQservice manual download site
quQservice manual download site
After seriously of observation, finally lane understand signal process, entered signal from behind pass line to Panel tones conversion switch, then to balance switch, out and with line received back of letter source conversion switch, conversion Hou with line sent to amplifier Board plug needle Shang, with oscilloscope observation on not difficult found, to amplifier Board entered end Hou signal tomorrow mourning weak and accompanied by miscellaneous wave, try with cleaning each conversion switch Hou, around channel volume are normal, but try machine several hours Hou left channel also is has murmur. After replacing a new source transfer switch fault completely ruled out.quQservice manual download site
quQservice manual download site
This machine is the ' 89 products, so with until now time is short, this machine without human damage is generally not serious damage, over time the most obvious fault is the aging of the switch knob, clean updated through a series of tone still does not reduce in those days.

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