Identifying transformers??

[wildbill hickup]

I have collected a few transformers from different power supplies and TV boards and would like to make use of some of them. However I can't seem to find any listings of part numbers (similar to Xing IC's) I have googled till I'm blind and don't seem to be able to come up with any information scimatics, inputs, outputs, manufacturers, etc. The particular on in question This time) comes from an old TV, numbers on it are LT174F 004T TCE 9321 Rev. B there are 16 pins 8 on a side and the only marking is on one pin marked MS. Can anyone point me to some sort of identification listing or is there no such thing?  If not, short of hooking up to AC and checking other pins for voltage how can I test these things to get an idea of what they do (ratio, 1 to 1 isolation, etc)

[johnlm]

I really don't think there is an kind of cross reference for transformers.  They almost always go into a specialized application and there has never been much of any kind of multiple company sourcing in the way there is for transistors and ICs.  Although there may be many companies build similiar transformers, they have not ever been given any kind of JEDEC types of numbering scheme so there is not much of a way to cross reference by the using the manufacturer's in house numbering that may be on them.  

With simple transformers that have a single (115 or 230 V) primary and only a couple of low voltage secondaries you can experiment with them and usually come up with at least knowing which terminals go to the primary (usually a much higher DC resistance winding) and then find out which terminals make up secondary outputs by finding continuity from terminal to terminal.  From that point you can try connecting the primary to 115 V and see what kind of output voltages you get on the secondaries.  Trying to determine the current rating of the secondaries is not so easy.  And some transformers were not even made to connect to a primary voltage of 115 or 230 V such as those found in switching power supplies.  In general unless you know what application it came out of and whether it was meant to be connected to 115 or 230 on the primary, it is pretty difficult (and sometimes possibly hazzardous) to get any real good information on them short of maybe contacting the manufacturer, and even then they may not give you any info except maybe to tell you it was made as a custom unit for company XYZ and they cannot give out any details.

Johnlm

[terry5732]

I have found that in many items i've torn apart the transformer was the only problem component.

And 99% of the time it was a component added to the transformer to protect it that actually failed. There is a small overload device which cuts power if it overheats. Usually found wrapped in transformer under about the top two layers of tape. Just an unbelievable failure rate on these. Especially in wall warts.

Just to play with connections to get ratios, you could try feeding with an old 24 VAC power supply like for toy trains or such. You could still get yourself a tickle and spill your beer but not so dangerous.

None of these little transformers will have output ratings of greater than 500mA to maybe 1 amp. Generally, big output needs big transformer.  You can use these to get get 120 VAC from 12VDC but you would be limited to applications using less than about 12 Watts!

A good place for a little heavier transformer to step up 12 VDC to 120 VAC is an old battery charger - the heavier the better. Pick up every cheap one you see at garage sales. Two heavy duty rectifiers in each too. And maybe even an ammeter. The older ones which were switchable to charge 6 or 12 volts are center tapped - perfect for an inverter.

[oztules]

hmmmmmm... very few trannies will be off the shelf components identifiable with a useful code so blind bushranging is the order of the day.

1. mains voltages are dangerous. if your not conversant and comfortable with them seek personal guidance from some slob who is

 that being said lets get on with the meat and potatoes part..

2. If it has not got metal laminates, chances are it's not for mains use (torroidal core trannies excepted)
   
3. If you have reason to believe it is from the power supply part of the device and it is not a ferrite tranny surrounded by ic's and fets, chances are it is a power tranny
   
4. try and use an isolated power supply for the mains supply. If you have two say 12v power transformers, connect the two secondaries together ie 12v to 12v. now when you drive one of them with the mains it will step down to 12 then back up to mains voltage in tranny no2. This will be isolated, and to get a shock you will have to hold both wires. If you have rcd fusing in your property, then you could disregard this step as very good protection is provided by the residual current devices.
   
5. wire a mains voltage 20watt incandescent lightglobe in series with your test ac line. Its purpose is to stop the test tranny from becoming an incendery device. If the input you have chosen is wrong, the light will glow. If the light stays off you have in all probability found the primary
   
6. using meter test all the windings for ohms. the highest resistance stands the best chance of being the primary.
   
7. drive the "primary" with the lightglobe in series. If it is the primary, the light will be off, and you can read mains voltage on the ac scale off the meter accross this winding. Check the other windings for their respective voltages and note all readings. job done. (if the other windings have no readings, then primary is open)
   
8. If globe glows, then this is not power tranny, or you have hooked up the wrong winding. go back to step 6 . I the globe  still glows and the test winding is the highest resistance winding then.... not a power tranny.
   
   

once again, if you are new to mains power, then seek guidance from someone in person who is familiar with these voltages and the foibles of mains electricity.... be respectfully afraid, many people have not had a second chance. Its 240v over here and packs a lethal punch.

hope this helps..........oztules

 

[drdongle]

There are no cross references for these transformers because they are built to order for each product and not "generic". Simplest way to reuse them is to trace the circuitry before you take them off the board. ID the 120 V primary first then IDing the secondaries is simple.

And the thermal protection on the primary is often the problem with open primaries. simply cut the first few layers of tape and when you find it, bridge it with a peace of wire and glue the tape back down.