Ashly MFA-8000 manual Troubleshooting Tips, No Audio Output, Distorted Sound, Hum or Buzz Noise

Operating Manual - MFA-8000 and MFA-6000 Power Amplifier

11.TROUBLESHOOTING TIPS

11.1No Audio Output

Power switch not lit:

Line fuse is blown or power outlet is dead.

Power switch is lit but no LEDs lit:

There is no input signal applied or input level controls are off. Note: In parallel mono mode, be sure that only one signal source is connected to the amp.

Protect LED and Limit LEDs are lit and relay clicking is heard:

Output is short circuited or load impedance is too low. Check speaker cables for shorts, increase load impedance by disconnecting some speakers.

A high frequency oscillation in the sound system is occurring when the relays close. Turn down the input level controls to verify that the ampli- fier alone is not causing the problem. Be sure to use good quality shielded and balanced input cables. Do not run input cables alongside output speaker wires over long lengths.

Protect and Limit LEDs are lit, Clip LED comes on as soon as input signal is applied:

DC voltage may be present on the output or an internal 15 amp type MDA slow acting fuse on the amplifier circuit board may be blown. Have a qualified technician replace the fuse with the same type of fuse.

Protect LED and Limit LED only are lit:

This is the normal status for the first 2 seconds after switching power on. If this status contin- ues, the amplifier may be protecting the speak ers from an abnormally high frequency and high amplitude signal. The problem may be with the signal source. Try disconnecting the signal source from the amp.

Protect LED and Thermal LED are lit:

Amplifier is in thermal protect mode due to extreme overheating. Allow better ventilation, reduce signal levels or increase load impedance by disconnecting some speakers.

11.2Distorted Sound

Output level meters indicate 0dB level (red CLIP LED on):

Amplifier is being clipped. Reduce the signal level at the signal source.

0 dB level on output meters is never reached:

Applied input signal is distorted before it gets to the amp. Check to see if a piece of equipment in the signal chain before the amp is clipping. Nor- mally the amplifier should be operated with input levels fully CW to maximize headroom in the signal source. Also check for damaged speaker drivers that could cause distorted sound.

If distorted sound is still heard, there may be an internal problem. Call Ashly Audio service department at 800-828-6308.

11.3Hum or Buzz Noise

Be sure that the power cord’s 3-prong plug is con- nected to a properly earth-grounded outlet. Lifting the grounding third prong usually does not improve hum or buzz and creates a potential electrical shock hazard.

Use balanced input connections with a balanced audio source for best hum and buzz rejection. See section 7.1 on inputs.

Normally the ground lift strap on the input screw terminals should be left in place for best ground voltage suppression. In some cases hum or buzz noise may be induced by excessive ground current through the input ground connection. This current path may be interrupted by removing the ground lift strap. If the problem persists, input signal transformers providing complete ground iso- lation are available. See section 8.1 on Input Isolation Transformer.

Buzz noise can be caused by lighting dimmers or neon lights. Try moving the amplifier, wiring, or light- ing to different locations to see if lighting is the source of the buzz. Input transformers may also fix the problem. See section 8.1 on Input Isolation Transformer.

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