Do not open the amp. No user serviceable parts inside the amplifier.
Make sure the voltage selector switch on the left side panel is set properly (115V/230V) before plugging the amplifier on the AC outlet.
Never use the amp at a high moisture environment or near liquids.
The Microtubes 900 can deliver more than 115 db of power. Exposure to this level of sound can damage your hearing. Use proper hearing protection if you will be exposed.
The Microtubes 900 can deliver more than 900 Watts. Be sure that your speaker cabinet is able to handle that power. You can reduce the output of the amp by selecting the 2Ω mode on the rear panel (by the Speakon output jack).
Do not cover the vent holes. The Fan and vent holes are part of the cooling system of the amp. Covering the vent holes can produce overheating of the power amp damaging it.
Do not use an instrument cable as speaker cable. An Instrument cables are not design to deliver power signals going from the amplifier to the speaker.