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Can I combine old powers supplies to supply higher voltage/amperage to one device?

QUESTION:

I have dozens of 12v, 9v, 6v, 5v, 4.5v, and 3.7v power adapters laying around, but need a 24v 2a power supply. I know with batteries you can simply daisy chain them together (sequentially) to attain higher voltage (as is done in most electronic devices) or in parallel to address higher amperage needs. Is there a simple way to do this with power adapters? (could I throw the inner workings of two 12v 1a power supplies on a board, and connect them in such a manner as to acheive the equivalent of 24v 2a? My guess is no. If not, is there some way I can somehow utilize parts from my vast collection of powers adapters, to create a 24v 2a adapter?

SPECIFICS:

Let me preface the remainder of this by saying that I have no training whatsoever in electronics, or circuit design, other than what I picked up from my "101 in 1 electronics set" when I was a child. I am however, (I've been told) pretty sharp, and due to an overwhelming need to understand how everything works, have learned a few things over the years (mostly by taking things apart), and am now able to diagnose and repair most broken home electronics that I have so far encountered. (DVD players, CD drives, laptops, desktop computers, monitors, tvs, whatever) I have deduced that most electronics malfunction due to a failed connection of some sort rather than bad components.

I have an old iBook (Blueberry), which no longer has a power adapter. (in retrospect I should have saved the part, which only had a frayed wire - and had caused a short) Apple incorrectly diagnosed the iBook as "fried" along with the power adapter. (my 2nd replacement, the first two adapters met death in the same manner - frayed connector)

I have since determined through tinkering (and plugging in a friend's adapter) that the iBook is functional. In fact, now it works better than it did before! (Due to the fact that I thought it was broken, I have since fully dismantled the iBook in order to understand it's inner workings, and in doing so, discovered the source of the CD drive failure (bad CD-ROM drive which I replaced with a CD-RW from my Dell that just happened to fit), and the USB port failure, (broken connectors) and repaired the USB port by hammering copper speaker wire flat then bending it into shape, and replacing the 4 contact points inside the USB port, which I then saudered to the motherboard. (I didn't have enough "wire" to apply sauder to when I first attempted to simply sauder (together) the original connectors that had broken))

What I need is a 24 adapter, which I would prefer to make one myself rather than pay money money for another crappy replacement that will eventually fray again anyway, I am unemployed right now, so I can't really afford a new one anyway.

That being said, do I really even need 24v? I know just about all computers that I have tinkered with seem to have two internal supplies,

12v and 5v. (all devices/boards are subsequently designed to use one or in some cases both of these power supplies, at least this has been my observation) Would there be a relatively simple way to connect a power block from one of my old desktop macs? (I'm assuming that the 24v DC gets converted to 12v, and 5v immediately after the power enters the computer. Where would I want to connect the 12V & 5V? (what am I looking for on the motherboard? unfortunately everything is very small, and labeled only with letters and numbers that no doubt mean something to someone with an Apple iBook Repair manual but are apparently meaningless without one.

And, as for the jack, I already have this covered. (It's just a mini stereo jack. the outer connector simply powers the light on the jack reciever) (Although if I decide to use a power brick from a destop Mac, I will fashion a new conncector of some sort. I suppose just a standard internal power connector (Red, Black, Black, Yellow) for desktop computers would suffice, and be otherwise appropiate.

I welcome your comments and suggestions!

David Franklin

Reply to
Daaavey
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Its been said here a few times that putting pc switch mode power supplies in parallel or series is problomatic and may break the supplies, you might get away with it if you dont draw much current, but if one shuts down the other one can destroy by reverse driving current through it.

Ive converted a SMPS to run at higher op voltage before, but it needs a reasonable amount of experience, and a great deal of care to not cuase electrocution ! It involves rewinding one of the secondaries and using beefier diodes and changing the voltage feedback network and current limit to suit.

I also used a much beefier IGBT for the switch on the input, for simplicity I removed the components from all but the one output. in fact with a higher voltage switch it might not be necessary to rewind the transformer just use the highest winding. ofc it depends on the topology of the primary stage. if the transformer is heavily varnished/encapsulated/glued wich many of them are then rewinding is unlikly to be possible.

However it can make a usefull high power power supply.

Colin =^.^=

Reply to
colin

That iBook uses a shrouded power connector that will not be available from any source other than Apple or Apple's third-party addon suppliers.

Two good options: (1) go to an Apple dealer and get the power supply (as a repair part, it's probably still available). (2) get a third-party or used power supply but BEWARE newer iBooks use a different connector, and the eBay picture won't tell you for sure. The old black power supplies for black Powerbook G3 are compatible, if you can find them.

The box of random power adapters is unlikely to help, because this is a forty-plus watt adapter, and most little wallwarts are good for more like 3 watts. If you could come up with a combination, it'd take $30 worth of power strips to plug 'em in.

Since you're willing to do repair, finding a dead adapter and dissecting the cable for rewiring might work; beware trying to take the saucer apart, though, it's glued with solvent-weld joints and does not disassemble gracefully. You gotta repair one with a break at the tip, not at the saucer joint.

Reply to
whit3rd

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