A coworker came in last week with a little mini amplifier (a Fender Mini Tonermaster®) that had stopped working. Being the curious sort, I opened it up, and looked at the main board. I immediately saw that D1 was physically blown (top half had blown off, and was rattling around inside the case). I figured this was probably the only issue, and brought it home to replace that diode (a simple 1N4003). After replacing it, however, the amp still didn’t work… which is why it’s nice I had it at home since I have the gear needed to diagnose the problem there. =)