18
Unusual output conditions
The vast majority of amplifier faults show up as
high positive or negative DC output voltages.
An independent circuit in the Halcro amplifiers
senses any unreasonable DC. output voltage
and switches the amplifier off if this occurs.
Likewise, if any excessive output current flows
for an extended length of time, this also
implies a fault and an independent circuit
measures this and will shut down the amplifier.
Power supply output current
limiting
To further reduce the possibility of fault
conditions causing substantial damage, the
power supply is limited in its maximum
available average output current. Note that
this level is higher than the amplifier’s normal
current limiting conditions. The power supply
limit will only cut in under fault conditions.
Internal power supply
protection
There are numerous power supply protection
circuits, for example:
•
two independent over temperature cut
outs
•
two independent master clock fault
sensing circuits
•
all power supplies, including those for
“housekeeping” Standby, active power
factor correction and switch mode power
etc check for under/over voltage and
over current conditions
•
the small signal power supplies have
transient diode over-voltage protection.
Mains transient overload
protection
The mains input is protected against all but the
most severe mains input transients. Three
independent circuits achieve this: two surge
absorbers and high energy inductive filtering.
Input overload protection
The inputs have over-voltage protection
circuits, which will handle most typical input
overloads.
Amplifier inter-stage
protection
In addition within the amplifier stages, there
are more than a dozen protection circuits.