I usually use DC 'wall warts' - Interesting! I hadn't measured an AC one, I just let someone else use those, usually. I didn't anticipate any real drop in voltage - guess I forgot about internal resistive losses inside the transformer, which is already part of why a DC plugpack "peaks" sans load. Need a vacation here, obviously I used to use a DC Lump, put it through a reverse protection diode for safety , then a fuse & Zener for over-voltage protection (cheaper: Use the reverse protection diode AS a fuse, not ideal but cheap! Even lower cost: Skip the series diode, put DC In - Fuse - Reverse diode to ground, or skip the fuse & let the plugpack's diodes blow if you must ) Then a nice Cap, regulator, etc. I'm migrating to using a bridge rectifier for input protection, (yeah, you lose 2 diode drops, but it's always SAFE, and it's cheap, and accepts DC or AC input. ) True, on the rest I like the recent trend to try to use different plugs for different voltage ranges; Even though it is a pain in terms of finding all those sockets, makes it less likely that someone will plug a 15VDC plug into their 4.5VDC device, then complain to the manufacturer about poor design quality Hoping Chris gets a new plugpack! Mark Jinx wrote: > > Correct, I know exactly what you mean about DC plugpacks. I would > still not trust a label and consider it prudent to measure the AC voltage. > You never know what, if any, standards the manufacturer has. If you'd > agree that a loaded transformer's voltage will drop, then it's not > unreasonable to suggest that a manufacturer could install one with a > higher voltage that will drop to the stated voltage at the stated load. > As an example I have a small labelled 18V 0.3A AC adaptor for a > UV EPROM eraser (no retification or caps at all). It measures 20.3VAC > unloaded but 17.4VAC in use. > > Whether we agree or agree to disagree I think a point about not > assuming labelled voltages on plugpacks is worth mentioning. I've > stopped at least one of my customers blowing a circuit I'd made for > him by checking his chosen 4.5V plugpack before he used it. Admittedly > it was a DC one and if he'd been in the know he could have expected > it to be as high as it was (7.5V). With so many low voltage CMOS > devices now on PCBs and the consequent general reduction in current > required, if you aren't using a regulator you'd be ill-advised not to check > a bought plugpack (please don't think I just said you give ill advice). > > All of this is academic in Chris' case. It looks as though the supply he's > got will be inadequate anyway. > > WBR Jinx. > > > > BTW, Jinx, not true that you'll see 15VAC out unloaded - We're not > > talking after rectification here, but before - when you don't load a DC > > supply, it peaks up (and also you see less ripple than at heavy loads > > > > > > Mark > > > > Jinx wrote: > > > > > > If the figure of 200mA is on the label then that will be the current > > > at the labelled voltage. In all probability the unloaded voltage will > > > be higher, perhaps 15VAC. > > -- I do small package shipping for small businesses, world-wide.