Parasound A 31 Problems and Remedies, Unit will not turn on, No sound from speakers, Overheating

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Total Protection - Current Overload

Specialized current-sensing transistors are connected to the output stages of the A 31 to constantly monitor the current flow through the output transistors. If the current drawn by this stage exceeds a predetermined safe level due to a load impedance below 1 ohm or a short circuit at the speaker terminals, the output relay will open immediately to prevent any of the output transistors or other parts from failing.

Total Protection - Fuses

Each channel of the amplifier has a separate fuse for its positive and negative DC voltage rails. These fuses provide backup protection in case the over-current protection does not work in time, or if an internal part fails. In the event of a part failure, these fuses halt operation to minimize damage to additional parts.

Problems and Remedies

Unit will not turn on

•Check the setting of the Turn On Options switch. (The front panel On-Off button will be disabled if the switch is set to Audio or 12V)

•If using Audio Turn on, try increasing the sensitivity of the audio trigger by turning the audio threshold knob to the “Quieter” position.

•Check that the AC power is live.

No sound from speakers

•Check that input cables and speaker wires are secure at both ends.

•Make sure the surround preamp is switched to the correct input.

•Is the Hi-Temp light illuminated? All three blue channel indicators should be illuminated. Check for excessive temperature, short-circuited speaker wires, low impedance speaker load, and inadequate ventilation.

Background Hum or Hiss

•Move audio cables and AC cords away from each other.

•Try different routes for the audio cables and AC cords.

•Make sure insulating shoulder washers are used if unit is rack mounted.

•If you have cable or satellite TV, try disconnecting the incoming TV or satellite cable; if hum is eliminated you will need a Cable TV Ground Isolator or contact your TV service provider for assistance.

•Try turning down the input gain controls

Overheating

•Remove any nearby external sources of heat such other audio equipment or heaters.

•Increase ventilation around the A 31.

•Check speakers for faults

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Contents OWNER’S Guide Important Safety Instructions Table of Contents Parasound Staff Keeping Records for Future Reference Important Warranty informationThank You for Choosing Parasound Unpacking Your a Unpacking Your a 31 & Placement GuidelinesAC Mains Voltage Rack Mounting Your Parasound a Audio Input Connections Audio ConnectionsSpeaker Connections Speaker Wire Length and Gauge thicknessSpeaker Terminals Correct Speaker Polarity is ImportantWhen to Set the Gain Control Knobs Above or Below Normal Gain Control SettingsManual Position Turn On OptionsAudio Position Automatic on/off 12V Position Automatic on/offVolt Jacks AC Power Cord12V In Jack 12V Loop Out JackOn-Off Button Front Panel OperationGround Loops Eliminating Hum and Buzz Technically SpeakingBalanced and Unbalanced Lines Power Supply Bare Speaker Wire EndsParasound a 31 Design Overview Circuit Designed by John CurlRelay-Bypassed Soft Start Circuit Complementary ConfigurationAudio Circuit Path Topology Input StageClass A-A/B Operation Output StageTotal Protection DC Servos Total Protection RelaysUnit will not turn on Problems and RemediesNo sound from speakers Background Hum or HissAre You Having Difficulty? Repair or ServiceSpecifications Parasound Products, Inc McKinnon Ave, San Francisco, CA
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