I went through this amp about 6 months ago and updated it with all the Harbach mods. Was using it in CW/Tune on SSB last eve. when I hear a noise inside by the diode board RM-220. Shut the unit down and opened it up. D17 was shorted on the board, D16,D15 appeared different also in the diode check with my Fluke . I went ahead and changed all the diodes on the RM220 and checked the resistors. Next I checked the filter caps, all appeared good with cap checker, but D4 on the cap board was also shorted. Anyone have any thoughts on what could have caused this failure ?