Cambridge Audio 840A - Manual (Page 20)

20 Azur Class XD integrated amplifier
If the unit has not fully cooled down then the temperature may reach the
limit soon after the amplifier is powered up. If the loudspeaker
impedance is low the temperature of the amplifier may rise faster as the
amplifier is working harder. If the amplifier is mounted in a cabinet or the
ventilation slots are obstructed the over temperature detection may
activate/reactivate after a short listening time.
Remedy - User related fault. The internal temperature of the output
transistors has reached the over temperature limit. The unit is not
damaged, although it should be left for 15 minutes to cool down before
pressing the Standby button to resume normal operation.
3. Overvoltage/overcurrent detection
Indication - The display flashes “OVERLOAD”.
Description - CAP5 offers V/I protection by constantly monitoring the
output transistors to keep them working inside their Safe Operating Area
(SOA). The SOA is a set of limits given by the output transistor
manufacturer to ensure reliability. The 840A deals gracefully with brief
periods of overload by controlling the drive to the output transistors. If
the overload is sustained for a period, the output relays disconnect the
amplifier from the loudspeakers and the display shows a flashing
Cambridge Audio has developed a proprietary protection system to
ensure reliability and a long life to its amplifiers. This protection system
comprises of five main protection methods:
1. DC detection
Indication - Unit has switched off during operation, display flashes “DC
ERROR”.
Description - CAP5 offers loudspeaker protection if the output of the
amplifier goes to a high constant voltage (DC) because of some internal
fault. This is a rare fault although detecting it could just save those
expensive loudspeakers.
Remedy - Due to the necessary sensitivity of the DC protection circuit,
hard clipping of the amplifier may cause DC protection to be triggered.
If this fault occurs please switch the unit off, power up again and check
operation with a reduced volume level. If the DC fault occurs again
please contact your dealer for service.
2. Over temperature detection
Indication - Unit has switched off during operation, display flashes
“OVER TEMP”.
Description - CAP5 includes temperature detection which constantly
monitors the heat generated by the output transistors. If the monitored
temperature reaches a high level (suitably within the limits of the output
devices) the amplifier will automatically switch into a fault mode. The unit
should ideally be left for 15 minutes in this state to cool down adequately.
CAP5 - FIVE WAY PROTECTION SYSTEM
Mode
Volume
Mode
Volume
Mode
Volume