Servicing

SAFETY.

These safety notes are directed to those testing and repairing this power supply.

Legal requirements mean that we must not encourage untrained personnel to take the lid off.

Servicing should only be carried out by a competent service engineer.

This supply contains mains voltages on the voltage select PCB, the mains switch, etc, and the usual precautions must be taken.

The main reservoir capacitors have a capacity of 20,000 uF, and are charged to +26V.

THIS CAN BE DANGEROUS.

The danger lies not in the voltage, but in the large currents that will flow if the capacitor terminals are shorted. A small screwdriver will simply disappear in a violent explosion. The main bodily danger is from metal watchstraps, etc. Serious burns are very likely if these contact the capacitor.

For safety reasons, the reservoir capacitors are discharged by bleeder resistors at switchoff; this takes about 10 seconds.

The unregulated supply to the +48V regulator can reach +90V on high mains, and should be treated with some respect.

Initial operational tests on the power supply can be carried out by switching the unit ON and checking the voltages present on the output connectors on the back of the unit. While the unit remains disconnected from the mixing console some of the DC voltage rails are floating with respect to each other, that is they do not all have a common reference within the unit. When connection is made to the mixing console various output pins become earthed to a common star-point, which has a mains earth return in the power supply cable itself.

An indication of obvious fault condition is the failure of one or more of the front-panel LED’s to light.

Any fault condition, with the exception of simple mains fuse failure due to underrating or an unusual mains input condition, will require removal of the top cover to enable fault correction. This is achieved using a cross-head screwdriver to remove the six retaining screws and washers. Carefully lift the cover to avoid the earth connecting lead to the cover from snagging. Place the cover face down behind the unit.

WARNING: At the front of the unit just behind the front panel is the MAINS SWITCH, which carries HIGH VOLTAGES directly from the mains input. Similarly on the rear panel is the MAINS INPUT SOCKET/MAINS VOLTAGE SELECTOR.

Care MUST be taken when carrying out any servicing operation with the top cover removed.

Technical Description

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SoundCraft CPS250, CPS275 technical manual Servicing, Safety
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CPS250, CPS275 specifications

SoundCraft is renowned for producing high-quality audio mixing consoles that cater to a wide range of audio professionals and enthusiasts. Among their notable offerings are the SoundCraft CPS275 and CPS250 power amplifiers, which combine innovative technologies with reliable performance.

The SoundCraft CPS275 is a powerhouse designed to deliver a robust output with exceptional clarity. It features a dual-channel configuration, providing 275 watts per channel into 4 ohms. The CPS275 is built with a solid-state design, ensuring high efficiency and minimal distortion, making it suitable for both live performances and studio applications. One of its distinguishing features is the advanced thermal protection system, which safeguards the amplifier from overheating, ensuring longevity and reliability even in demanding environments.

On the other hand, the SoundCraft CPS250 is a slightly smaller model, ideal for users seeking a balance between power and portability. It offers 250 watts per channel into 4 ohms, making it perfect for smaller venues or monitors. This model emphasizes versatility and sound fidelity, featuring a class AB circuitry that enhances audio accuracy while maintaining low noise levels.

Both the CPS275 and CPS250 come equipped with comprehensive protection circuitry, which includes short-circuit, overload, and DC protection. This guarantees that both amplifiers will perform consistently without risking damage to connected equipment.

In terms of connectivity, these amplifiers feature XLR and 1/4-inch TRS inputs, allowing seamless integration with a wide array of sound systems. Additionally, the CPS series employs efficient cooling systems, ensuring optimal performance without the risk of overheating even during prolonged usage.

Both models are designed with rugged construction, making them suitable for the rigors of touring and live events. They are equipped with rack-mountable chassis, allowing for easy installation in professional setups.

Overall, the SoundCraft CPS275 and CPS250 amplifiers exemplify the brand's commitment to delivering high-quality audio solutions. With their advanced technologies, protective features, and exceptional sound quality, they cater to a variety of audio applications, making them an excellent choice for professionals in the music and live sound industries. Whether powering large PA systems or smaller setups, these amplifiers are engineered to meet the demands of any audio environment with impressive accuracy and reliability.
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