| Symptom | Likely section on schematic | Component | |---------|-----------------------------|------------| | Loud hiss, crackle | Preamp input stage | Q1, Q2 (2SC458 → replace with KSC1845) | | Chorus weak or distorted | BBD bias trimmer | Re-adjust VR5 or VR6 per service manual | | Chorus dead | Clock or BBD | MN3101 pin 6 / MN3004 pin 7 | | One channel dead | Power amp or preamp summing | STK module or IC4 (summing amp) | | Hum, low output | Filter capacitors | C1, C2 (main filter caps ~4700µF/50V) | | Reverb not working | Reverb driver/recovery | IC (usually NJM4558) + tank connections |

The Roland JC-120 Jazz Chorus Go to product viewer dialog for this item.

Here's a breakdown of the JC-120 schematic:

Features the same clean preamp but adds the legendary Chorus, Vibrato, Reverb, and Distortion circuits. 2. The Stereo Chorus Circuit

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Jc-120 Schematic Jun 2026

| Symptom | Likely section on schematic | Component | |---------|-----------------------------|------------| | Loud hiss, crackle | Preamp input stage | Q1, Q2 (2SC458 → replace with KSC1845) | | Chorus weak or distorted | BBD bias trimmer | Re-adjust VR5 or VR6 per service manual | | Chorus dead | Clock or BBD | MN3101 pin 6 / MN3004 pin 7 | | One channel dead | Power amp or preamp summing | STK module or IC4 (summing amp) | | Hum, low output | Filter capacitors | C1, C2 (main filter caps ~4700µF/50V) | | Reverb not working | Reverb driver/recovery | IC (usually NJM4558) + tank connections |

The Roland JC-120 Jazz Chorus Go to product viewer dialog for this item. jc-120 schematic

Here's a breakdown of the JC-120 schematic: | Symptom | Likely section on schematic |

Features the same clean preamp but adds the legendary Chorus, Vibrato, Reverb, and Distortion circuits. 2. The Stereo Chorus Circuit The Stereo Chorus Circuit

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