TOA Electronics TA 1400 - Manual (Page 15)

9.1.2 Thermal protection
If the amplifier is driven very hard into a low impedance load, the cooling fans will run at high speed.
If the causing conditions continue, the Temperature indicator(s) will illuminate indicating that the
amplifier is about to go into thermal shutdown.
After five seconds the amplifier will go into thermal protection by muting the input signal. After 15-20
seconds the amplifier will have cooled down enough for the amplifier to come out of shutdown and
operate as normal. If the load conditions remain unchanged the thermal protection will be reinitiated.
Thermal protection starts when the Intercooler
® heatsink reaches a temperature above 90 0 C.
9.1.3 VHF protection
If a signal above 12kHz is detected at the amplifier outputs for more than five seconds at full output
power, the VHF protection mutes the input signal. (This is indicated on the front panel (
2 ) labeled
Protect). After five seconds the outputs will un-mute and return to normal operation, unless the
output signal has remained unchanged, in which case the VHF protection will re-initiate.
9.1.4 Short circuit protection
All Tannoy amplifiers are completely short circuit protected. The protection circuit permits very high
peak currents, but still holds the output devices within the safe operation area. If a short circuit is
maintained, the channel affected will eventually go into thermal protect cycle until the short circuit has
been removed.
9.1.5 AC mains voltage protection
If the AC mains voltage is over the allowed operational voltage, the power supply will automatically
shut down. Once the mains voltage is above the minimum start voltage and below its maximum
operating voltage the amplifier will restart.
9.1.6 D.C. protection
There are two types of DC protection:
• Fuses on the supply branches of each channel.
• A DC crowbar protection that shorts the output if more than 10 volts DC are being detected
on the outputs. Both these circuits come into effect once a DC level are beeing detected on
either channel.
10 MAINTENANCE
Under normal use the amplifier should provide years of trouble-free service. The only user
maintenance required by the user is to vacuum 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 (-40dB) is illuminating there is nothing wrong with the amplifier; the likely
cause is an unsecured Speakon speaker connector.
Check also that the VHF protection is not activated. If it is, remove possible high frequency
oscillations from the relevant input.
Fault: The amplifier goes into thermal protection when driven at low level.
Check that nothing causes a short circuit at the amplifier's output, e.g. any component in the
loudspeaker (this can occur when the speaker coil gets warm).
Fault: The amplifier goes into protection with power indicators off.
Check that the AC line voltage is within the amplifier’s operating range, 130-265V@ 230V, (65-
135V @ 115V). Over-voltage protection may have occurred. If the amplifier is connected by
Tannoy Limited
TA 1400 User Manual 11-06-02
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