RCA Trafo Data // CRV Series

[MrG]

Hey all,

Looking for any data on the ‘40s/‘50s era RCA CRV series trafos. I just picked up an output trafo and can find no data thus far. Any ideas would be extremely helpful - thank you very much to anyone in advance!

Best,
MG

 

[CJ]

What does it look like? Can you post a pic?

Does it look like it would come apart very easily?

 

[emrr]

You won't find any, you have to figure out what it came from and/or take measurements.    CRV is Military I believe. 

 

[mjrippe]

What is the CRV number?  Any other markings?

 

[MrG]

Hey folks,

Thank you very much for your replies and time. I will be receiving this tomorrow and will be sure to take photos and update here with info. It’s (possibly painted?) black, so doesn’t look like others I’ve seen.

This brings up something I’ve never been able to put my finger on: I get checking for DCR, but how does one actually analyze impedance via test signals/processes? Any info would be much appreciated.

Thanks all,
MG

 

[MrG]

Hey all,

Received the trafo in good condition for its age, photos are below. Looking forward to hearing your thoughts!

Thanks much,
MG

 

[MrG]

And another! No writing anywhere :/

 

[emrr]

Small signal sized.  9xxxxx # series falls early 50’s.

 

[MrG]

Thanks, Doug. Could you please tell me what that practically implies? Like what range of impedance broadly?

And how might I measure them other than listening to test signals (which I’ll do)?

Thanks!
MG

 

[Brian Roth]

First of all:  figure out "which pin is which" by measuring the resistances.  From that, you'll be able to suss out more details.

Bri

 

[emrr]

Thanks, Doug. Could you please tell me what that practically implies? Like what range of impedance broadly?

And how might I measure them other than listening to test signals (which I’ll do)?

Thanks!
MG

It doesn't imply much.  Certainly nothing about impedance.  Measure the DCR and make a connection chart as Brian said.  Go find the old threads about measuring unknown transformers, there's a ton of information here about this.  DCR will give a pretty big clue about impedance, but nothing about response. 

 

[dmp]

If you don't have test equipment, look for a wall wart that has an AC output. Pretty easy to find. Just cut off the end and attach alligator clips to the leads.
Measure that with the AC voltage measurement on a multimeter to see what your test voltage will be (V_test).
Then put that on different terminals, and measure the other terminals with the multimeter.

For instance, if the primary were 1&2 and the secondary were 3&6, say you apply the AC test voltage to 1&2 (V_test) and measure the voltage on 3&6 (V_measure), you can get the turns ratio as V_test/V_measure.
If it were a 10:1 transformer, and your V_test=9v, the V_measure would be 0.9v.
Depending on what pins you hook up you may get strange or misleading results. Best to find the windings that have continuity with DC ohms, then impedances with AC volts.

If you want to know the impedances, the (turns ratio)^2 = Z_primary/Z_secondary
i.e. for a 10:1 transformer, the impedance would be 60k:600 (which assumes the secondary is 600 ohms).

A small signal transformer is most likely either an audio input or an audio output and they can both have multiple taps. Look at the RCA BA-2 schematic to see what the taps *might* look like for an input & output transformer.  The transformer numbers are labeled on that schematic and you see they have the same 901xxx-501 format.

 

[emrr]

It's also possible it's a power transformer.