Hi All

I am desperately trying to fix a Christmas marching band for the Kid's xmas tree. The device itself is originally from America, however it was plugged directly into a 230V supply with no inverter and therefore has probably fried the transformer. I am going to replace the transformer and thought I might as well replace it with a 230V transformer to remove the need for a voltage inverter. I have found a transformer and think I understand how to wire it up, however a small question the power to the board is 2x6v, I assume this as the board has 2 red wires going to it with 6v printed on the board next to each input, (I am waiting for a reply from the manufacturer to confirm the output required from the transformer) however there is a white wire next to the 2 red ones which is designated "CT". Does anyone know what this means and what's its for, the transformer I propose to buy doesn't seem to cater for a CT wire? I have attached a picture of the board and a tech sheet for the transformer. The board was manufactured approx. in 1993 so its pretty old.

Many thanks

 

Try VTX-126-100-206 if you want a 100 VA size.
Then use the first drawing with purple marks on it to see how to do a center tap.

 

Many thanks for your reply #12 however I Am still none the wiser on what the CT is?

 

Center tap

 

Your circuit will use a Centre Tapped transformer like this...

 

Hi Dodgydave, thanks for your reply. I now understand what the CT stands for and what it is. My next question based on the mains transformers I have found (I have attached a spec sheet) do I need to use the CT wire, is it just a case of wiring a 230V wire to the inputs and bridging as per the spec sheet and taking the 2 x 6v red wires and connecting to the outputs, then in theory it should work right? As the transformer is not a centre tap transformer or should I be looking for a centre tap transformer?

 

No, you must use a Ct transformer, search for a 6-0-6V transformer.

 

If that IC is damaged, then you will have to spend 50 to $75 to find a set of Marching Santas on ebay.

 

Further to the above post, am I correct in saying the old transformer was really old and therefore outputted 12v and the CT was to split it to 2x6v whereas the new transformer already does this and the CT is not needed?

 

If that IC is damaged, then you will have to spend 50 to $75 to find a set of Marching Santas on ebay.

Well I am hoping its not damaged, fingers crossed

 

Hi Dodgydave, thanks for your reply. I now understand what the CT stands for and what it is. My next question based on the mains transformers I have found (I have attached a spec sheet) do I need to use the CT wire, is it just a case of wiring a 230V wire to the inputs and bridging as per the spec sheet and taking the 2 x 6v red wires and connecting to the outputs, then in theory it should work right? As the transformer is not a centre tap transformer or should I be looking for a centre tap transformer?

The "center tap" is the center of -6 and +6 for an overall 12V transformer. The center tap becomes the ground (zero volts) and the other two phases (positive 6 volts and negative 6 volts). The center tap is NEEEDED or you will have no connection to ground.

 

should I be looking for a centre tap transformer?

No, you're looking AT a center tap transformer. Just make a connection where the purple mark is on the drawing of the secondary windings and THAT is the center tap. See? It's in the center of the windings!

And you have to use it. Connect a wire from the center of the output windings (the purple mark) to that place on the circuit board marked, "CT". You will have to use a piece of wire to connect the center tap of the transformer to the place marked, "CT". It should be about 16 or 15 gauge wire. (Somebody translate that into British for me.)

Or you can go look for a center tapped transformer with the wire already attached.

 

No, you must use a Ct transformer, search for a 6-0-6V transformer.

Ok so i

No, you must use a Ct transformer, search for a 6-0-6V transformer.

Ok so is it ok to replace the 110v with a 230v as long as the output is the same? and I guess the CT goes to the 0 element of the transformer?

 

Yes, you need a 230V to 6-0-6v transformer.

 

Ok so i

Ok so is it ok to replace the 110v with a 230v as long as the output is the same? and I guess the CT goes to the 0 element of the transformer?

Yes, your transformer will have a pair of wires for your 230VAC and three exit wires (one odd color). The odd color is the center tap.

 

Those Tfrs mention they are dual winding which implies 2 separate windings, if so they will require phasing if they are not marked in order to set them up as a CT style.
The picture also shows twin secondaries.
This is the same as a CT when wired this way.
Max.

 

Hello,

You can also get transformers with two separate primaries and two separate secondaries.
Those can be connected as followed:



Bertus

 

Hi Everyone thank you so much for your time and effort to reply. If I were to check the IC to make sure its not damaged before purchasing a transformer how would I do this? with a multi meter?

 

You could test it with a couple of batteries, the 6vac in would be equivalent to ~9v-0-9v DC supplies after capacitor filtering.
Max.

 

You could test it with a couple of batteries, the 6vac in would be equivalent to ~9v-0-9v DC supplies after capacitor filtering.
Max.

you lost me on the capacitor filtering