Couldn't you just measure with a multimeter before opening? I use discharge resistors that are good with under a second. Unfortunately they're warm, so probably not fit for a case that size. However they mount on the chassis, so that helps dissipate heat. They're 50w, but only bleed a couple watts a piece. They seem perfectly reliable. I don't know what yours are, but it's nice to not have to worry. I suppose in a PFC network their values may be a determinate, however.