I had an ABM for years, every now and then it needed a good clean out, remove the gear tray and blow everywhere out with an airline first, get in the jacks etc and around the eq sliders, then liberally spray everywhere with servisol from maplins whilst turning sliding pushing and pulling every knob and control as you go, leave it stood on its end for a good few hours to dry out, connect it up and enjoy the hiss and crackle free goodness
done it at least four times to mine, give the cooling fan blades a wipe down too.
sorry for the lack of caps i have a bust arm!