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Ways to test a transformer

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Nostrafus

New Member
Aiight, I got this circuit I want to duplicate (it broke, was made poorly, and want to remake it with better components) and the transformer has only one marking on it, no serial or anything, and I'm afraid to strip it to pieces to look for it as I may not be able to rewind it and get the same performance for testing what kind it is.

Anyone got any ideas.

Marking is 18, can't tell if it's on primary or secondary as the windings are covered by shrink plastic.
 

Nostrafus

New Member
I was thinking hooking up a AA to the primary windings and then use a multimeter on the secondary and getting the ratio so I can figure out what it is.
 

mattg2k4

New Member
Holding a AA to a transformer won't give you much to work with, a single up and down cycle of the voltage then the AA is applied and removed. I don't know if a multimeter will be able to measure this, but if it can it will only appear for a second and you might not catch it.

A 555 square wave generator could be hooked up say at 60 Hz (seeing as how that's the frequency of mains here), or if you're feeling fancy, you could turn that into a sine wave generator. Or just hook it up to mains. That might be a bit risky, since mains is mains, but it would certainly be easy.
 

stevez

Active Member
I agree with avoiding connecting to the mains - too dangerous. You could take a doorbell transformer to drop the mains voltage to something safe ( the sine wave generator is best but not sure you have access to one). Then take a small light bulb (bulb, not LED) with a voltage at least that of the doorbell transformer that will act as a series resistor to limit the current - and apply voltage to one side momentarily and measure the voltage across the transformer leads on the input - then on the output. The ratio of the voltages should tell you what you want to know. What you won't know is how much current the windings can take. There is a crude rule of thumb for total power rating of a transformer based on the cross sectional area of the core but I don't have access to my manual at the moment.
 

Jamesj

New Member
Let me start by saying Im a newbie. I have completed a few projects. But not a whole lot. anyway... I have a transformer, robbed from a apc back ups 1250. No findable data. it has 120v input but 4 outputs, 2 spade terminals and 2 red wires between them 1 wire is 14 gauge the other is 10 gauge. I measured it at 16.26vac (either wire to spade) and 32.5 vac spade to spade, wire to wire was 0v. The amps on my fluke were like 8.6 (16v) and 19.9 (32v) I didnt have a load on it or anything. Just plugged into the wall. I want to build an adjustable power supply for projects ranging from 3vdc up to 50 or so if possible. Can it be done with this?
 
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