NIKKO NR-719 Power Amp Distortion

[Dingus Khan]

Hello all,

First post! Schematic here:
https://www.hifiengine.com/manual_library/nikko/nr-719.shtml


I have a Nikko NR-719 that passes signal through both channels, but the left side is distorted when pushed, especially with lots of bass. I don't have a scope but characteristically, it sounds like crossover distortion.

Checked the bias for the left side and I'm getting 0mv regardless of trimpot position. Right side biases up no problem. I traced the voltage through a little bit, found that at the emitter of q705 I have about .5V as opposed to the 1.2V listed in the schematic.

What could cause a loss of bias voltage in this amplifier? I am very familiar with tube guitar amps, but stereo receivers are a newer to me.

 

[felixleg]

Hello all,

First post! Schematic here:
https://www.hifiengine.com/manual_library/nikko/nr-719.shtml


I have a Nikko NR-719 that passes signal through both channels, but the left side is distorted when pushed, especially with lots of bass. I don't have a scope but characteristically, it sounds like crossover distortion.

Checked the bias for the left side and I'm getting 0mv regardless of trimpot position. Right side biases up no problem. I traced the voltage through a little bit, found that at the emitter of q705 I have about .5V as opposed to the 1.2V listed in the schematic.

What could cause a loss of bias voltage in this amplifier? I am very familiar with tube guitar amps, but stereo receivers are a newer to me.

Trying to get the service manual but I'm not a HiFi Engine member. Anyone knows how to get it?