One of the quirks with those Performas having a slide-out motherboard concerns oxidization that can develop on the gold-plated contacts/pins along the edge of the motherboard, compromising the connection they make when engaged in the main slot from which individual wires run to the DB-15 display port, the optical and hard drives, front panel audio and speaker, etc. If the pins on the motherboard aren't making a good connection within the slot, you can experience odd problems with any of those items mentioned. To correct this, you should remove the motherboard, lay it on a non-static inducing surface (like a newspaper), and then gently scrub the pins along the leading edge of the board (upper and lower sides) with a soft, white eraser. Don't use a pink-colored pencil eraser. They'll probably have a dark gold appearance before you begin, but will be much brighter/shiny afterward. Be sure to blow off any residual rubber shavings, prior to re-installing the motherboard. Reconnect everything and see if the problem has been eliminated. The previous recommendation about replacing the motherboard's 4.5-volt alkaline battery is always a good one for those Macs. Unlike most of Apple's computers of that period that used a 3.6-volt ½AA lithium battery (that rarely tends to leak), the alkaline battery in those Performas is notorious for leaking solution, after it has been dead for a while. I've seen motherboards ruined by the corrosion left in the path of the leak. A date that reverts to 1956 every time the computer is unplugged from AC power is a good indication that the battery is shot.
