If the amp hums but has no sound, check the filter capacitors (large 4700µF or 6800µF caps). The schematic shows their exact location in the rectifier bridge.
One speaker plays the dry signal; the other plays the pitch-modulated signal.
“The chorus is a lie. The two voices are never equal. One always arrives late. That’s the beauty. That’s the tragedy. To fix it is to kill it. But what if I make the delay infinite?” jc-120 schematic
The JC-120 has two channels: Normal and Bright . The schematic shows a classic JFET (Field-Effect Transistor) front end.
Whether you are trying to recalibrate the bias on the output transistors (the schematic lists the bias voltage as a specific mV drop across emitter resistors), or you are trying to replace a dead BBD chip, If the amp hums but has no sound,
But schematics are not passive. They are stories told in the language of voltage.
This is the magic. The schematic shows an BBD chip paired with an MN3101 clock driver. “The chorus is a lie
R117: 1k (no, 2.2k? no—silence) C23: 47uF (replace with 100uF, bleed faster) D4: 1N4148 (remove. bridge. let it flow both ways.)
