TOA Electronics TA 1400 Maintenance, Troubleshooting, Thermal protection, VHF protection

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 900 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	14
TA 1400 User Manual	11-06-02