JBL A6000GTi, Service Manual, Page: 17 / 62

137159-1 Rev. 1 A6000GTi Service Manual
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2003 Crown Audio, Inc.
Theory Of Operations 3-6
disabled, and a crowbar circuit is employed to drain the rail voltage to prevent any further
damage.
3.2.4. Thermal Limit Control (TLC)
The TLC circuit is used to control the output of the amplifier while monitoring the
temperature of the amplifier output devices and of the power supply switching devices.
When the devices begin to overheat, the TLC circuit begins to compress the input signal,
scaling back the output power until the unit is capable of cooling itself again.
On the input board, U104-C and U104-D form a window comparator with the input signal
and two DC voltages created by U110-A and U110-D. As the unit begins to heat up, the
window narrows, and when the input signal reaches the upper or lower limit on the window
comparator, the compressor drive circuit is activated and the input is compressed in the
same manner as IOC.