Vox Ac30 Service Manual [2021] Now
Service Manual: Vox AC30 (Legacy and Custom Classic Series) Disclaimer: Tube amplifiers contain lethal voltages (400V+ DC) even after unplugging. Capacitors can remain charged for days. If you are not trained in high-voltage safety, do not open the chassis. Proceed at your own risk. 1. Model Identification & Topology | Model | Years | Key Features | Quirks | | :--- | :--- | :--- | :--- | | AC30/6 TBX (Handwired) | 1990s-2004 | Turret board, GZ34 rectifier, Celestion Blue speakers. | High noise floor if lead dress is disturbed. | | AC30CC2/X (Custom Classic) | 2004-2010 | PCB, 12AX7-driven rectifier sim, Master Volume, optional Wharfedale speakers. | Susceptible to ribbon cable failure. | | AC30C2 (Current) | 2011+ | PCB, digital reverb, FX loop, GZ34 rectifier. | Digital board grounding issues. | Core Schematic (Common to all):
Input: 2 channels (Normal / Top Boost). Preamp: Three 12AX7 (or ECC83) – V1 (Normal), V2 (Top Boost), V3 (Phase Inverter). Power: Four EL84 (or 7189A) in cathode bias (Class A push-pull). Rectifier: GZ34 (5AR4) or solid-state.
2. Troubleshooting Flowchart Symptom: No sound, pilot light off
Check mains fuse (T2A 250V for 230V, T4A for 115V). Check power switch continuity. vox ac30 service manual
Symptom: No sound, pilot light on
Test: Tap V3 (phase inverter) with a wooden chopstick.
Click heard? Fault is in preamp. No click? Fault is in power amp (EL84s or OT). Service Manual: Vox AC30 (Legacy and Custom Classic
Check HT fuse (usually inside chassis near rectifier). Measure voltage on pin 3 of EL84s: Should be 11-14V DC (cathode bias). If 0V, cathode resistor/cap is shorted.
Symptom: Loud hum (120Hz)
Culprit: Filter capacitors (the large silver/black cans). Replace if >15 years old. Quick test: Lift one leg of the first reservoir cap (32+32µF). If hum stops, cap is leaky. Proceed at your own risk
Symptom: Thin, fizzy distortion, low volume
Cause: One or more EL84s are red-plating (runaway current). Fix: Replace the matched quartet of EL84s. Do not mix old/new.