The Symptoms

Nothing more on the LCD than an amber glow of the backlight, no response to keys, backlight and LEDs of the tubes need longer to dim on switch off.

Technical Background

The ESX has five internal powerlines: +/-12V, +5V, +3,3V, +1,8V. The 12V is for the tubes and amps, +5V and +3,3V is mostly used for IOs of the Microcontroller, ADC, DACs etc. The 1,8V supply is needed for the digital part (core) of the embedded microcontroller. The fuse, which protects the 1,8V LDO (Low Drop Out), is blown, so the uc can't work.

How to Fix it

Open the ESX: Remove the plastic knobs by pulling them. Unscrew the allen keys. Remove the front. Remove four "golden" screws, not the black ones. Remove the panel holding the knobs. Look on the upper right side for a bunch of capacitors. Below is a SMD called "FUSE1". Measure the voltage on both sides of the fuse. If the voltage on both sides is "3.3V", then your fuse is ok. If not, you have to replace.

I measured the current going through the fuse. With all LEDs on, I got 1.7A. I testet with a 2A fuse for a whole weekend of musicmaking, it worked. So use a) a wire, if you're in a hurry or b) a 1206 footprint (I'm not sure about this) 2A fuse to replace.