Over-voltage. Voltage != current. :-) I think the concept is that the cap could have shorted out, thereby causing a too-high voltage to pass through it - or something like that! :-) In general, cause the circuit to mis-behave. I struggle with the analog circuits too. Just keep plugging away at it, each will slowly start to make sense. (Not the most complicated/sophisticated aspects, but if you understand a lot of what's going on, I'm sure someone here can help on the tricky bits.) DEC's maintainence/technical manuals are very good indeed for explaining how the analog circuits work - especially for those of us who can't just glance at a schematic and instantly, intuitively understand how the whole thing works. For me, reading them is really pretty much a must before trying to debug/repair analog stuff. This is where you need test instruments; an ESR meter (although that's not a universal solvent), a capacitance meter, etc, etc. (Also an ohmmeter, to check for shorted caps.) If you seriously expect to repair something like an 11/45, at a _minimum_ you need a decent 'scope. Don't even _try_ thinking you can do it without one. Fuhgeddaboutit. I like Tektronix 465's - they are common on eBay, and if you're patient, you can get one for $60-70. They are also a 'scope much used on these machines BITD. (We did.) Past that? Well, there are things that are nice to have (e.g. a de-soldering station), but you can often work around them (e.g. a pair of dikes and a solder sucker). A logic analyser would be nice, and I keep meaning to get one, but I haven't, yet, so they aren't essential. (Although for _some_ faults, a 'scope just doesn't cut it. If you can write a loop, fine. If not... time for a logic analyzer.) I'm trying to think what else is absolutely essential, past the 'scope (and the meter - you ought to buy your own, they aren't that much). Nothing comes to mind immediately - perhaps someone else here can add to the list. Noel