Help me to identify a couple of old transformers.

[jpm83]

I couldn't find any datasheets for these. Here are the pics.



Janne

[JasonG]

I would recommend taking a dmm to them. Judging from the picture your pulling those from a 60's (?) board. Knowing what they came from would help identify track down the specks. Those could be in house numbers used by the electronics manufacturer so you may never get the data sheets.
When working with old and odd electronics its good to get as much info as you can before you take it apart. If its working you can get the operating voltages for the device you want.
Measure it , de solder it , label it and put it in storage.

[jpm83]

Those are from an old transistor cassette radio. I have already de-soldered all of the trannys (which were PNP germanium) and some other stuff too. The manufacturer of this radio is National Panasonic.
   What should I measure and how from these transformers? I was hoping if they could have been used in octavia or in some other guitar effect stuff. I have this kind of DMM. http://support.metermantesttools.com/meterman-sales/download/asset/2277152_a_w.pdf

Janne

[Zben3129]

Well if you know which side is the primary, you can hook up a 12v ac if your in US or a 24vac tranny for places with 240v. Measure the voltage on the secondary (ac), and multiply by ten. Thats your vac out.

Zach

[jpm83]

Does this apply to the impedance tramsformers also? One those is connected some how to the cassette decks motor and I think that one is in the mic preamp and for the third I don't know where it's connected.

Janne

[jpm83]

The Manufacturer and Model were: National Panasonic Model RF-520LBS. Matsuhita Electric idustrial CO,. LTD And I live in Finland so it's rated to work with 220V AC.

[Zben3129]

Ok so...

use a 22vac transformer on the primary.

You can use the voltage out to determine impedance ratio aswell. There is a guide on this somewhere, but basically you find turns ratio and multiply by the load. Ill find that guide in the next few minutes.


Zach

[Zben3129]

I can't find that guide, but I believe I remember the formula...

First, get the primary:secondary ratio, known as turns ratio. This is simply vacIN:vacOUT. If you put 22v on the primary and get 1v on the secondary, your ratio is 22:1

If you do not get 1v on the secondary, multiply or divide the secondary number by whatever it takes to get 1. Then, do the same exact thing to the top number. (IE if you get .75v on the seconday, your ratio is 22:.75  however, we want  x:1, so multiply .75 AND 22 by 1.33 to get 29.2:1 ratio)

Now, square the larger (primary) number. 22 * 22 = 484. 484:1 is your impedance ratio,

Now, to reach reflected impedance on primary, multiply by the load.

For 8ohm speaker, you'd have 484 * 8 = 3872:1

for 16, 7744:1

for 4ohm, 1936:1


Formula is - turns ratio squared, times the load.

(22:1)²*8=3872:1


Zach

[jpm83]

Thanks for replies. How critical that 22vac is because I can find only transformers that give me 16vac, 6,45vac and 9vac.

Janne

[Zben3129]

You can use any of those. The only reason I suggested 22 is because it is 1/10 of your wall voltage, so you could just scale your voltage out by 10. Now, just set up a proportion.

1 number over another = 1 number over another.

Assuming you use 16v transformer....

So basically the math for this is multiply your Vout with the 16 (or 9.5, 4....etc)v xformer by 220v. Then, divide that result by your known transformers voltage to get the voltage out of the transformer under test with 220vac in.


Reasoning:




16vac       Scale Vout AC
_____  =  ____________

220vac     True Vout AC






so if you got 1vac out using a 16v transformer, you would have (220v)(1v)=(16v)(xv)......this would give you 13.75 voltson the secondary with 220volts in