DIY - Nikko NA-550

Taking the measure of restoration before quiescent current. A photograph of the card. Use a marker to identify the polarity of the capacitors. Change capacitors one by one to avoid an error. Treat welds and pay close attention to the polarities. Before reconnection, do a check of the cards.

Adjusting the BIAS.

Setting the quiescent currents (powers of the amplifier circuits). Do not apply signal to the input of the amplifier, volume 0. Output terminals of senior speakers: nothing connected. Use only a multimeter, and know the precautions and safety measures face a unit. The voltages in the device approaching 250 volts!

Left Channel:

Adjust the variable resistor (R729) check the voltage across points (TP 35 et TP 36),
and set to 9 mV quiescent current.

Right Channel:

Adjust the variable resistor (R730) check the voltage across points (TP 37 et TP 38),
and set to 9 mV quiescent current.

Results:

A transformed amplifier, much more musical, more detailed. A very well built device, to discover the plastic began to be used.