Two channel power output measurement point voltage, there is a clear negative pressure, indicating power amplifier "failures". In order to distinguish between "failed" on which channel, disconnect the Rl (note, not speakers).JFjservice manual download site
JFjservice manual download site
After startup, find relay to pull-in properly, test-point voltage, right back to normal, left channel remains at negative pressure, indicating "failed" in the left channel. Online measure the resistance between the left channel of amplifier tubes are in compliance with the PN junction electrical properties, no circuit breakers and suspected breakdown. Measured by comparative method of two-channel transistor resistance to ground, find the VT10 base resistance than corresponding tube of the right channel, doubts the VT10 is not normal. Remove the VT10, between b and e was open circuit. After the replacement, "failed" excluded.JFjservice manual download site