> regulation of excellent xformers can be 10% or less and with very
> cheap wall warts it can be 30% or worse. A cheap 6.3V @ 100mA
> xformer may deliver 6.3V + 30%  = 8.2V with no load

That's something you need to be aware of when using wallwarts/
plug-packs/battery eliminators. A neighbour of mine was caught out
badly when he used a higher amp 12V in an alarm system. The
circuitry was designed to load the original p-p down to 12V. When
he swapped that p-p for another, the circuit loading had virtually no
effect and the system saw 18V rather than 12V. Not a forgiving
design, and it was his fault, but still .........  You have to assume that
most people do not have a DMM and wouldn't know or care how
a transformer works. They see the "12V" and that's what they were
looking for

I recently picked up a load of plug-packs (thank you Russell) that
are unregulated and nominally 12V @ 150mA. Open circuit they
measure 19.2V or +60% !!!!! That's OK, I knew that beforehand
and have the circuit designed for them. There's a label on the blister
pack (but not on the p-p itself unfortunately) stating

"WARNING - UNREGULATED. Output voltage will be higher if
your appliance draws less than the rated current"

Dangerous if you don't know the implications of that - especially as
the warning is not on the item but rather on the packaging, which
would typically be in the bin pretty smartly - and I'll be including
more specific information in the product's manual as well as moving
the warning sticker to the p-p


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