Aguilar DB 751 Mode D'emploi page 6

Diagnostic and Protection
The DB751 is equipped with a self-diagnostic and status/protection circuit.
Upon power-up, the unit's blue status LED will blink for approximately 45
seconds. During this time several circuit parameters are verified, or al-
lowed to become self calibrated.
1. The high B+ voltage to the preamp tubes is slowly ramped up, allowing
the tube heaters to warm up before full current is drawn by the valves.
2. DC offset at the amp's output is monitored. Only if none is present
(normal condition), will the unit proceed with the self-check protocol.
3. Temperature on the MOSFET heat sink is checked, and again only if
normal temperature is detected, will the status check continue.
4. If all the voltages, offsets, and temperature are in accordance with
factory specifications, then the amp's input, and output relays will be
energized. This will then cause the operate LED to illuminate and the
status LED to stop blinking. The amp is now ready for normal operation.
5. The circuit continues monitoring the above parameters to protect both
the DB 751 and the speakers connected to the amp in the event of unit
or user error. This will be indicated by the status LED's blinking.
6. If the status LED continues blinking, or starts blinking during amplifier use,
this indicates a system fault. The amplifier requires servicing in order for
normal operation to resume.
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