Kensington and iGo both make universal power supplies that can be used to power various devices using special tips to configure voltage and current settings. I've often wondered if these could be hacked to use as lab supplies. A recent find of a Kensington 70 watt supply led me to do some experimenting.
I'm happy to report that both of these power supplies can be used as low-cost bench power supplies with adjustable voltage and current limiting. The Kensington types in particular are great building blocks for simple knob(pot)-controlled to more featured microprocessor-controlled supplies.
Kensington supplies provide 0 - 25 volt outputs at up to 6 amps. Voltage and current are each controlled by a pair of resistors in a voltage divider arrangement. A digital pot or DAC output can easily control these supplies.
iGo makes two types of supplies - a laptop supply and an "accessory" supply. The second is what I experimented with. It's more limited with a 3.1 - 9 volt range at up to 1.5 amps. Voltage and current are each controlled with a single resistor.
The details can be seen here:
Kensington SuppliesiGo SuppliesEither type of supply can be bought new for $15 or less. Add a few parts and you can have a nice bench supply.
Hmm, i'll try and find one of them in my city 
Man, kensington no longer sells them so no go.
If anyone is willing to sell me one, i'm all up.
I dug up an old Belkin Universal Adapter I had and it was identical right down to the pin-out of the connector. These instructions worked beautifully. Unfortunately I killed a component whilst trying to tear it apart. Can someone help me figure out what the little coil next to the mains inlet labeled 470 is? I want to try my hand at replacing it.
Says made in the USA!!!
In this pic you can see the component I broke;
BigER pics here;
http://www.flickr.com/photos/thespeedphreak/sets/72157629973057051/
i made something similar out of a targus 90w supply a while back. its adjustable from 15 - 24V, but i don't recall pins for current. i'll have to take another look....
-sj
Hmm, i'll try and find one of them in my city
Man, kensington no longer sells them so no go.
If anyone is willing to sell me one, i'm all up.
Here you go Dave. I just ordered 2 for myself.
Send me a message. How much did you pay for it?
I've heard these things are pretty fragile when out of the case. I'm going to leave it intact and connect it via the cable.
its pretty much useless outside of its case
fragile is an understatement
Those are active switches, used to improve conversion efficiency by removing the diode drop. Nice PCB planar transformers there, that board must be multilayered, 12 at least, to get the primary side small enough to fit in the layering under the ferrite caps.
Good thread. I just bought one of these to fool around with.
I've been messing around with these thing for a couple of years now. I've opened three of them to build programmable supplies. All three are now dead two because some random wire on my bench would fall into the board and make it pop. One mechanic while breaking open the case. There are a couple of very good reasons for getting them opened however. One is they cool much better. I added a heat sink were they ran hot. In there case you will find that they start to shut down due to heat if run at full power for a long time. The other advantage to getting inside there is that there is a continues 12V available (approximately) that is nice for running your programmable supply electronics. You'll find that voltage near the 12V input connector.
So there you go. Good Luck. If you are careful and don't make the same dumb mistakes I made you can gain something by breaking one open. But don't blame me if it breaks.
Cheers,
Dave
P.S. If some one needs a part contact me I have spares.
I've been messing around with these thing for a couple of years now. I've opened three of them to build programmable supplies. All three are now dead two because some random wire on my bench would fall into the board and make it pop. One mechanic while breaking open the case. There are a couple of very good reasons for getting them opened however. One is they cool much better. I added a heat sink were they ran hot. In there case you will find that they start to shut down due to heat if run at full power for a long time. The other advantage to getting inside there is that there is a continues 12V available (approximately) that is nice for running your programmable supply electronics. You'll find that voltage near the 12V input connector.
So there you go. Good Luck. If you are careful and don't make the same dumb mistakes I made you can gain something by breaking one open. But don't blame me if it breaks.
Cheers,
Dave
P.S. If some one needs a part contact me I have spares.
THanks for sharing.
DaveAVR where are you located? I need one of those 470 mH chokes on the inlet side of things.
terabyte - Contact me with a private message and your address and I'll drop one in the mail. You can buy me a beer next time your in Oregon. - Cheers, DaveAvr
Has anyone made any measurements on the outputs? I'm curious about the quality of the regulation, switching noise etc.
Has anyone made any measurements on the outputs? I'm curious about the quality of the regulation, switching noise etc.
Mine arrived today. Here's a no-load scope trace before I go to bed.
I got a few of these from overstock.com to experiment with.
The ones that actually arrived were model number 38004. It says 120 W max on the case, but 90 W continuous in the specifications. I guess there are 30 extra marketing watts thrown in for good measure.
I don't see an obvious way to open it. Any hints? Is the case welded shut?
The shiny top panel is held on with strong sticky tape.
Okay, that appears to be a ruse. I got it off and no screws underneath.