- Check all external fuses are intact.
- Obtain two RCA plugs that have been internally linked to form a short circuit input.
- Apply mains power check power LED. Do not connect speakers until a multimeter has confirmed that the DC reading at the speaker terminals (offset) is below 150mV, A typical value is 15mV.
- Leave the amplifier on and check it does not heat excessively under this no signal condition. This test is much better carried out by feeding the amplifier via a mains Watt meter like Electricity Usage Monitor Power Meter Plug Backlight Energy Monitor Plug Watt Meters 8 Modes, UK Socket Power Monitors Large LCD Display Consumption KWH Amp Volt Meter Outlet : Amazon.co.uk: DIY & Tools. The power consumed should be about 5W for amplifiers with a toroidal transformer. Some older Crimsons had a laminated transformer in which case expect up to 10W.
- Check the heatsink temperature using a IR thermometer such as KETOTEK Laser Thermometer Gun Infrared Thermometer Digital Non Contact Food Thermometers -50℃ – 600℃ (-58-1112℉) IR Thermometer Professional Grade Temperature Tester Recorder (not for human) : Amazon.co.uk: Business, Industry & Science Expect a few degrees Celsius above room temperature under no signal conditions.
- Power down for three minutes and then connect a known good signal source. Then power on and connect speakers to play quiet music. Again heat and power consumption should be minimal at 5W/10W as above.
- Crimson power amps have no click suppression at power up or down to preserve a solid direct connection to the speaker, The PCBs are designed to minimise on/off transients. Should the on/off click or thump be excessive or have any other added odd noises, there could be a transient instability at play which will need a bench test.