The JVC SEA-E30B is a Stereo Graphic Equalizer designed to provide precise control over audio frequencies, enhancing sound quality and allowing for personalized audio profiles. This service manual combines both the service manual and parts list, dated December 1984.
Function Description:
The SEA-E30B functions as a 5-element graphic equalizer, allowing users to adjust specific frequency bands to tailor the sound output. It includes input and output terminals for line-level signals, as well as tape monitor and tape recording connections, enabling its integration into various audio setups. The device features an indicator for visual feedback and incorporates a muting circuit and a constant voltage power supply for stable operation.
Important Technical Specifications:
- Input Section:
- SEA input impedance: 47 kohms
- Tape input impedance: 47 kohms
- Output Section:
- SEA output impedance: 300 ohms
- Tape REC output impedance: 300 ohms (during SEA recording)
- Rated output: 1 V RMS (with SEA system flat)
- Maximum output: 4.5 V RMS (with SEA system flat, 0.5%)
- Total harmonic distortion: 0.01% (20 Hz - 20 kHz, rated output)
- Gain: 0 dB (with SEA button ON, SEA system flat)
- Frequency response: 10 Hz - 50 kHz (+0, -2 dB)
- S/N ratio: 110 dB (at rated output, IHF A-network short-circuited)
- Control Section:
- SEA center frequencies: 31.5 Hz, 63 Hz, 125 Hz, 250 Hz, 500 Hz, 1 kHz, 2 kHz, 4 kHz, 8 kHz, 16 kHz
- SEA control range: ±10 dB
- General:
- Power source: See attached table (varies by region)
- Dimensions: 300(W) x 240(D) x 65(H) mm (11-13/16" x 9-7/16" x 2-9/16")
- Weight: 1.7 kg (3.7 lbs)
- Accessory: 2 pairs of one-touch signal cords (11 cm)
Power Specifications (Primary Fuse F001):
| Area |
Power Supply |
Power Consumption |
Power Outlet |
Fuse (Primary) F001 |
| U.S.A. & Canada |
AC 120 V~, 60 Hz |
6 watts |
Fitted |
QMF51U2-R20 (0.2 A - 250 V) |
| Europe |
AC 220 V~, 50 Hz |
8 watts |
Not Fitted |
QMF51A2-R20S (T 200 mA) |
| U.K. |
AC 240 V~, 50 Hz |
8 watts |
Not Fitted |
QMF51E2-R20SBS (T 200 mA) |
| Australia |
AC 240 V~, 50 Hz |
8 watts |
Not Fitted |
QMF51A2-R20S (T 200 mA) |
| U.S. Military Market & Other Areas |
AC 110 V - 120 V/ 220 V - 240 V~, selectable, 50/60 Hz |
8 watts |
Not Fitted |
QMF51A2-R20S (T 200 mA) |
Usage Features:
The SEA-E30B is designed for straightforward operation. It features ten slide knobs for the 5-element graphic equalizer, allowing for intuitive adjustment of frequency bands. Two push buttons are provided for TAPE MONITOR and SEA functions. The unit integrates into an audio system via its TAPE and LINE input/output terminals. The voltage selector, if applicable to the region, allows the device to adapt to different power line voltages (110V-120V or 220V-240V).
Maintenance Features:
The service manual provides detailed instructions for disassembly and parts replacement, crucial for maintenance and repair.
- Disassembly:
- Top Cover: Removal involves four screws on both sides and two screws on the rear panel.
- Front Panel: Requires pulling out ten SEA slide knobs, removing three screws, and two plastic rivets, then detaching the equalizer P.C.B. and the front panel.
- Analog Switch P.C.B.: Removed by two screws and fixing the pin jacks.
- Power Supply P.C.B.: Removed by two screws and pulling out the push shaft from the power switch.
- Service Precautions:
- Safety Parts: Parts marked with a triangle symbol on the circuit diagram and parts list are critical for safety. Only specified part numbers should be used for replacement.
- Wiring and Insulation: Metallic clamps must be covered with vinyl tubes. New wire insulation film must be 0.3 mm or more thick. Power cord replacement requires ensuring it does not come out when pulled. Power source related parts and wires must be bound and soldered, with at least 3 mm spacing between AC power line parts.
- LED Replacement: LEDs in the SEA volume control levers can be removed. Special care is needed when replacing LEDs, as adjoining LEDs are set with reverse polarity alternately. A defective LED can be identified by short-circuiting its leads; if other LEDs light up, the tested LED is defective. The part number for a single LED is AA3422K.
- Leakage Current Check: This is a critical safety check to prevent electric shock hazard. It involves measuring AC voltage and current across exposed metal parts and ground, and between exposed metal parts and the AC outlet. Measurements should be less than 0.5 mA AC (r.m.s.) or 0.7 V AC (r.m.s.) respectively.
- Voltage Selector: For models with a voltage selector, it is crucial to confirm the correct voltage setting before operating the equipment. The selector switch is located on the rear panel.
The manual also includes a block diagram, schematic diagram, and a comprehensive parts list, detailing transistors, ICs, diodes, capacitors, resistors, and other components, along with their part numbers, descriptions, and applicable areas. This detailed information facilitates efficient troubleshooting and repair.
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