An expansion on my post on your blog....
Nice one again! I am obsessed about standby power consumption and have a couple of Yokogawa WT210 power meters which I use to analyze appliances and such, which are very accurate down to the 5ma range. I have a Tektronix MSO4032 which has a big mechanical pushbutton switch on the front which I ASSUMED isolated the power supply circuit from the mains when off. After viewing your blog I hooked the MSO4032 up to the WT210 and here are my observations:
MSO4032 on: 238V (UK Mains), .361A, 77.54W (Mode RMS)
MSO4032 standby: 241.92V (UK Mains), 3.57ma, 0.0007W (Mode RMS)
Pics attached.
Sorry Dave, but I am not going to take my scope apart and look at the PSU circuitry, however I imagine that there may be some line filtering circuitry of such (e.g. MOVs) which result in some sort of measurable leakage current. The Yokogawa WT210 is an approved meter for Energy Star compliance and can be trusted to measure standby power consumption, and cost about £3000 each. (Amazingly the second unit was purchased on eBay for about £600.)
I agree that 6W standby is out of order in today's times. We are all fully aware of the environmental impact of energy consumption, and companies should incorporate features such as mains isolation into their product designs. Unlike a PC, TV or a set-op box, there is no reason to have a scope on standby.
I have gone as far as measuring the standby power consumption of supposed "green gadgets", such as a power strip that would shut off devices (e.g. DVD, set-top box) when your TV is turned off (i.e. UK Dragon's Den gadget from a few years back), and was saddened to discover that the cheap PSU that powered it drew 1W in standby, which was more than my TV consumed in standby! Oh well..........
Comox