Hello,

I was tasked with finding a replacement for a transformer that goes into one of our pcbs. The transformer is obsolete and as I am looking at different options. I am getting overwhelmed with drawing notations and naming conventions.

The transformer I want to replace is the Sprague-Goodman GLSW4M202. I assumed that pins 1 and pins 5 are the primary dot and secondary dot respectably. My board layout has pin 1 as an RF input pins 2 and 5 are grounded and pin 4 is the output. I did a quick test and inputted 1MHz 500mV sine wave into pin 1 and measured pin 4 and the sine wave was out of phase by ~180 degrees.


I have yet to find a transformer with this exact layout other than the Neosid 00 5532 00. (The only vendor I have found is italian and might be a bit difficult to get since I am based in the US atm.)



I've found several that might match. I am not entirely sure what the top end of the band limit I need but it is not 2000MHz.

While I am still on the hunt though can some one also explain what different drawing convention mean such as below:

Are those just different ways of drawing them? and should I just go with the the Pin configuration as that is less confusing?

Lastly, what about the ones with the center tap. Does it mean that I can get the primary output and secondary output and they are just out of phase? (assuming I keep a 1:1 core)


Thanks for taking the time to read.

 

The dot indicates phasing, i.e. same start direction for each winding.
What is wrong with the original, what about rewinding it if neccessary?
If rewinding, record all details when removing original windings.

 

The dot indicates phasing, i.e. same start direction for each winding.
What is wrong with the original, what about rewinding it if neccessary?
If rewinding, record all details when removing original windings.

Hello,

Thanks for the info. I understand the dot, but sometimes there are some weird drawings that go a little away from conventional drawings.

There is nothing wrong with the original only that it is obsolete and need to get something to replace it.

 

So if nothing is wrong, why replace it??

 

The transformer I want to replace is the Sprague-Goodman GLSW4M202. I assumed that pins 1 and pins 5 are the primary dot and secondary dot respectably.

Looks like a 1:1 voltage balun so your assumption is correct. You could theoretically also use it as a 1:1 current balun with the primary/secondary dot then being in different places.

My board layout has pin 1 as an RF input pins 2 and 5 are grounded and pin 4 is the output. I did a quick test and inputted 1MHz 500mV sine wave into pin 1 and measured pin 4 and the sine wave was out of phase by ~180 degrees.

Phase inversion is to be expected in your case.

While I am still on the hunt though can some one also explain what different drawing convention mean such as below:

Both examples are 1:1 current baluns.

You can use the first one also as a voltage balun, as a direct replacement of the obsolet Sprague-Goodman, but the achieved bandwidth would probably differ from the one specified in the datasheet.

The second example is a specialized form of a 1:1 current balun with a third, entirely separate winding for extended symmetry/balance down to very low frequencies. It is not a fit for your now obsolet transformer.

Lastly, what about the ones with the center tap. Does it mean that I can get the primary output and secondary output and they are just out of phase? (assuming I keep a 1:1 core)

You can use, as shown, a 1:1 voltage balun with center tap by simply leaving the tap open but it does not fit your current PCB layout.

 

So if nothing is wrong, why replace it??

They way I read the OP, he isn't trying to remove and replace a transformer on existing boards, but rather replace a transformer that is obsolete (as in not available anymore?) in the design for a product they have going forward.