I've been told that the trouble usually starts with the DC power source on old Delta 10/20 controllers. AC "ripple" effect, and dried out capacitors (old age) being most common. Check the Dynapath support page here http://dynapath.com/page_support_powersupplies.htm. If you are lucky, the trouble will end there. I have experienced the same WDT error you describe and am awaiting a final verdict from "Parts & Smarts."