On the previous page surround stage...
This board contains controller that manages all functions of the preamplifier. It has USART to controll VFD display, I2C interface to communicate with output triggers, relay input source selector and LEDs on the front panel. Software SPI interface handle PGA2310 chain. TL431 gives reference voltage for internal ATMega16 ADC to control VCC voltage and switch board voltage divider. ULN2004 is an output stage for triggers addressed from PCF8574.
I bought it on the internet. I suppose it is a display from check till. I've been very lucky to get two brand new ones. They are really simple to controll through the serial interface. The given light is rather green then blue but after using filters I've achieved quite a good results.
It is a simple resistor ladder to give various set of voltages depending on pushed button. On the board there is also I2C expander to controll front panel LEDs.
On the next page power supply...