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Old 23rd January 2005, 06:20 PM   #1
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Join Date: May 2004
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Question Transformer question?

Hi!
I could use some help.
I ran across a broken Ups (one iof those cans who are supose to power computers for a couple of minutes if the power fails).
Of course i took it home to see if i could use anyparts of it.

To my question. in the box there was a big transformer, a blown leadbattery and some broken electronics. Since i know very little of how one of these works iŽm kinda confused. when i took out the transformer which seems ok. there were 4 thin black wires running in which are all interconnected with eachother and 2 really fat ones coming out. however i have no idea what kind of voltage or currency it will supply.

there was also what apears to be an amp or a beafy voltageregulatur. 4 pices of aluminum roughly 100*100*4 mm with four transistors apiece, ie 16 transistors. the thing that confuses me the most is the fact that the fat wires were connected to these aluminum heatsinks!!
WHY ?

Is there an easy way to figure this out, Is it somekind of special transformer.?

Can i use it for say a multichannes chipamp.

Can i use any of teh other bits perhaps or should i just chuck the whole mess in the nearest garbagecan and keep looking?

sincere
Mcameron
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Old 23rd January 2005, 06:58 PM   #2
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It would be easier if you had posted a pictere, but anyway... The trafo is meant to charge the battery(ies). The thin wires shall be the primary (probably 2x115VAC, high voltage, low current). The thick wires are from the secondary (probably around 12VAC, high current). I am almost sure that it aren't 'transistors', but diodes on that heatsink.

This trafo has gost just one secondary. For a chipamp you need or two secondaries or a center tapped one, to obtain a + and - rail (and ground, off course). So, with this trafo you won't have succes. Find another one (so you can have + and -) or save it for a 'charging battery' circuit

You can save the heatsink, using them for the opamps.

And everybody is allowed to correct any mistake from my part.
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Old 23rd January 2005, 07:02 PM   #3
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Hi !!

I will try to explain how it works:
The ups uses high frequency switching supply to step up the
DC voltage from it's rechargable battery to 120VAC needed for
the computer.
It also has a special transformer designed for high frequency,
(with much less winding on it). DO NOT attemp to use it as
a regular transformer by connecting it to 120VAC !!
Now for the wires....
The transistors are usually high current mosfets, that are
all connected in parallel and connected to the transformer via the drain leg (the drain leg is also connected to the case of the transistor).
The designer simply connected all the drain legs to the transformer via the heatsink (which is a common connection
for all of them).

Hope I'v cleared things out a bit...

There should be another regular transformer for the battery
charger, though.


Best regards,

Udi.
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Old 23rd January 2005, 07:03 PM   #4
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Default Well then...

i got a new doorstop it seems.

Thanx for the quick reply
ciao
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Old 23rd January 2005, 07:30 PM   #5
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I'm sorry..I have a mistake in the explanation...
It is a LOW frequency switching supply and not high frequency
as I wrote. Everything else if fine.


Udi.
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Old 23rd January 2005, 07:52 PM   #6
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Yes you can use the transformer for a chip amp supply, the only problem is your going to need two of them.. Some expensive UPS's do have dual transformers though.

Anyway you connect the two transformers together at the low voltage outputs (the big fat wires, 14.5V AC). You connect the "hot" and "cold" wires together, making a ground and 14AC/14AC on each end.

The other 120V side of the transformers can be paralled with the mains. I very carefully tested which wires were the correct ones to give 14.5VAC on the output, watch polarity as well.


Once you are done you will have +/- 19VDC (should be fine for most chipamps) and some insane VA rating like 1400VA.

Here are a few pictures: transformers, final

btw you can use some of the parts if you want, theres a lot of filtering like X/Y caps, mains filters, and large inductors.
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