First allow me to apologize to the rest of the list for this off-topic debate. I was trying to throw an olive branch to Rick and not confuse the original poster with apparently conflicting information. I repeat we are all held to the same physical laws controlling how electronic devices behave. The immediate consequence of a shorted diode is to present the power supply reservoir capacitance directly across the transformer winding. Since large capacitors look like a short to AC voltage, large ripple currents will flow often leading to secondary failures if the transformer isn't adequately fused. Depending upon the rectifier topology, these large fault currents from a shorted diode may flow through other diodes in the circuit. In the case of a non-center tapped full wave bridge, the diodes opposite the shorted one will each carry the full fault current for half the time. One conducting during the positive half cycle, one during the negative half cycle. If the fault persists long enough one or both of these can fail too (from over "current" induced heating). JR PS: I won't bore the list with my full curriculum vitae but I've been designing electronic circuits for a few tens of years. I have managed an engineering department for a large music industry manufacturer and hold 8 US Patents.