unknown trafo

[AndersB]

Hi there.

I've been so lucky to get my hands on an old telephoneswitchboard - and it's loaded with trafos. the problem is that i don't know anything about them
(or very much of trafos in generel) I measured the resistance and the connections.

Could someone in here help to figure the ratings out (eg. 1:??) ?

TIA

Anders

 

[audiox]

Could be a hybrid trafo. Can you post a picture of the card where it is originally located? That could give a clue.

Most likely they have limited bandwidth making them not suitable for hifi audio (but there are exceptions). Probably easiest way to find out is to measure one of them with your computer soundcard. You can use for example RightMark Audio analyzer. It is free.

 

[AndersB]

Most likely they have limited bandwidth making them not suitable for hifi audio (but there are exceptions).

Well i thought of that too, but I'll try to run them thru the analyzer thanks for the help so far.

If you can se anything from the pictures or need some other closeupps please let me know

/Anders

 

[AndersB]

... And some photos...  :-[

 

[audiox]

There are no card edge connectors, so it can't be a "subscriber card" (don't know if that is the right term). There are not much analog circuitry either, so the analog part must be very simple. It could be a card that sends prerecorded messages to the telephone lines which are on hold. This is just a guess (without seeing the chip type numbers).

With 99% probability your transformers have very limited bandwidth. Even if they don't (I have that kind of "telephone" transformers, they are rare but do exist) they will saturate at quite low level. Signal levels in telephone systems are usually about 20dB lower than in pro audio. The relatively big size of the transformer is most likely because it is designed to work with DC hold current passing it.

 

[CJ]

flashed on some yellow lundahls in there, but no.

well, 11 ohms and 11 ohms is your balanced, 600 ohm primary, and since this is a fiberglass board coated with silicon, i would guess you have a secondary that would match up with a transistor, or possibly opamp?

so figure 2k, 10k,?

it is a step up, fo sho, you could use it as a low noise mic input, you do not need great response for human mid range, so don't worry about sweeping it.

wire it into an API or Langevin.

The dcr tells me that if you were yo rip that apart, you would find a U-I core with balanced coils on each leg.
i'm jus sayin...

 

[cuelist]

This is transformer by "Tradania" in Denmark. No longer around, probably now part of "Dantrafo".

 

[AndersB]

just seen that ter is something printet on the side of the trafo i says: 8431 - maybe it could help.

/anders

 

[CJ]

not a Lundahl number, everything the make starts with either a 1,2,3,5,6,7 or a 9.

 

[AndersB]

Well now I tryed using RightMark Audio analyzer. this is what I've found out for now. I Al so did a test with a 1 kHz sinewave to measure the dB - it's al in the pdf.

anyone got some useful DIY projects?

TIA

Anders B

 

[emrr]

That looks like it corresponds exactly to a Western Electric telephone transformer I've tested.  Probably a shared/licensed standard.