Let's start with the beginning. Are you sure you measured that AC output correctly ?
We'll have to know the output of the power brick is OK before we can blaim the AR-2.
Something you SHOULD check: The edge connector and the PCB "fingers" where it sits. The difference between the output of the +5V on the AR-2 and what you measure on the PCB is HUGE !!!
See if the connector has a TIGHT grip on the edge of the PCB, see if there is any burning or corrosion....
As you know there is a regulation circuit that will try to up the +5V output so be careful....