I have been checking out an iP4000 printer which was said to be working OK then suddenly stopped. When it is plugged in and switched on the power-on LED does not light. I have not pulled the switch out but with the top cover off I can access the switch terminals. I can't see them properly but there appear to be 4 of them (all soldered) though I suspect that 2 may simply be legs for mounting the switch on its small sub-board. One of the terminals registers about 3.4v (I think it was DC but may have been AC - tested some weeks ago). The switch is connected to the main board, not directly to the 230v phase. No other terminal is livened when the switch is turned on. I can't see any sign of a 230v standard glass fuse when peering around with the top cover off but haven't had the main board out. There may be one of those small thermal fuse thingees somewhere (can't remember what they're called).
Are there any other other tests/checks that a diyer can do (I know little about electronics)? Do these printers have a habit of open circuiting?