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

[Daaavey]

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

 

[colin]

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?

snip ...

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 =^.^=

 

[[email protected]]

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 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)

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.