Hafler p4000 Guida Utente

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The thermal protection is activated, and shuts down audio operation, when the amplifier heatsink reaches an
excessively high temperature. The voltage divider R22 and R23 establishes the reference voltage on pin 5 of U5B. The
control voltage on pin 4 is established by the voltage divider TS1 and R25. TS1 is a NTC (Negative Temperature
Coefficient) thermistor, mounted on the heatsink. As TS1 warms and the resistance falls, the voltage on pin 4 rises. When
the voltage on pin 4 exceeds the voltage on pin 5, the output on pin 2 goes low, shutting down the Soft Start switch Q1
and lighting the THERMAL indicator.

The CLIP indicator is driven by the comparator U5A. The voltage divider R56 and R57 established the reference voltage
for the Clipping detector at pin 7 of U5A. The reference voltage scales the output of U5A to indicate when the Drive
Signal, at pin 6, demands in excess of the available voltage or current of the output stage.

The SIGNAL indicator is controlled by the comparator U5D and the transistor Q8. The amplifier output is connected
to the input pin 9. The voltage divider R58 and R59 scales the output voltage to change the comparator output stage
at an equivalent input voltage of 30mV. The output at pin 14 controls the transistor Q8 to shunt across and turn off
the LED CR4.