Ac Mains Voltage Protection; Maintenance; Troubleshooting; The "Ac" Led - Martin Audio MA4.2s User Manual

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CONTENTS
If the AFS -limiter is activated, this will be indicated by the AFS-LED on the front panel. The AFS limiter will not be
activated during normal use, even under sustained heavy clipping
The AFS circuit is an advanced current limiter, allowing high peak currents, which do not significantly raise the
long-term average power, but limiting the current draw if a high continuous current is detected.
If the AFS circuit is activated, or if the power supply regulation goes out of stabilization, it will be indicated by the
AFS -LED on the front panel. The power supply could go out of stabilization at low mains voltage in combination
with low load impedance, during the start-up sequence.
If the average current draw exceeds the AFS trip level (during bench testing) the amplifier output power will be
reduced by 2dB. That is the same as an MA 4.2s being reduced to the power of an MA2.8s. This is preferable to
blowing a main breaker and the amplifier being turned off, as the only thing that is reduced is 2dB's of headroom,
which will not be noticeable on peaks of 120 – 130dB.
9.6

AC mains voltage protection

If the AC mains voltage is outside the operational window (over or under voltage), the power supply will
automatically shut down. When the mains voltage is above the minimum start voltage and below its maximum
operating voltage the amplifier will restart.
The two green 'ON' LED's indicate when the power supply is operating correctly.
It ta ke s a co up le o f seco nd s to se lf-ch eck (th is is kno w n as th e "so ft start" o r "slo w start" se q ue nce), the ga in w ill
slo wly a nd g rad ua lly b e incre ase d ba ck to th e pre viou sly set le ve l, an d the fan s w ill b lo w a t hig h sp ee d b efo re g oin g
into "id le ".
9.7

The "AC" LED:

This green LED indicates that there is mains power present on the incoming mains power conductors, and is a
safety requirement. Electrically it is located in front of the mains switch and soft-start circuit, and illuminates even if
the amplifier is off.
The MA4.2s uses a power-relay in the soft-start circuit, with a low voltage control switch instead of a high power
switch on the front panel. This method of power switching is more reliable and takes up less panel space than a
conventional power switch.
9.8 DC. protection
T he re a re tw o typ es of D C p ro te ction :

10 MAINTENANCE

Under normal use the amplifier should provide years of trouble-free service. The only maintenance required by the
user is to clean the front grill periodically.
In some extreme cases it may be necessary for authorized service personnel to clean the inside of the amplifier.
These conditions usually occur after prolonged use, e.g. in environments using "cracked- oil" smoke machines.
If you are using your amplifier for heavy duty use i.e. concert touring or industrial music it is recommended that you
have your amplifier serviced every 3 years, purely as a preventative measure.

10.1 Troubleshooting

These are typical things to check if you think your amplifier is faulty:
Fault: No output.
If the signal present LED (-40dB) is illuminating a signal is entering the amplifier; and the likely cause is an
unsecured Speakon connector, or loose termination
Check also that the VHF protection is not activated. If it is, remove the cause of the high frequency oscillations from
the relevant input.
Fault: The amplifier goes into thermal protection when driven at low level.
Check that there is no short circuit present at the amplifier's output, e.g. any component in the loudspeaker (this
can occur when the loudspeaker voice coil gets hot).
Fault: The amplifier goes into protection with power indicators off.
All material © 2007. Martin Audio Ltd. Subject to change without notice.
PRINT
F uses o n the su pp ly bran che s of ea ch ch an ne l.
D C crow b ar p rotectio n th a t sh orts th e o utpu t if m ore th a n 10 vo lts D C are b eing de te cte d on th e o utpu ts.
B oth th e se circuits co me in to e ffe ct on ce a DC le ve l ha s b ee n d etected o n e ithe r cha n ne l.
Martin Audio – MA4.2s Amplifier
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GUIDES