RCA transformer

Hello all, I just aquired a RCA SXMG-09 input transformer, and I can't find any info on it. I would like to make a tube mic pre with it, if it is suitable. Does anyone have any info?

Thanks,
David

Is that the only number on it?  No MI-xxxxxx #?  Could it be a Canadian variation?  Measure it. 

what did it come out of?

I don't know what it came out of, and there is no diagram on the can. Here are some ohms reading I took...

Pins
1-3  15.5 ohms
1-4  24.5 ohms

2-8  272 ohms
2-9  368 ohms

3-4  9.2 ohms

5-6  148 ohms

8-9  96 ohms

Every other pin combination is infinity

Thanks, forgive my newbieness
David

Here are some ohms reading I took

Click to expand...

So now you have magnetized the core of the transformer...

Gimme a break...

RuudNL said:

Here are some ohms reading I took

Click to expand...

So now you have magnetized the core of the transformer...

Click to expand...

try some audio into pins 1 - 4 and see what comes out of 2 - 9.

is pin 7 open to everything?
try from the can to pin 7 to see  if it is a ground/shield type deal

looks like utc pinout on the primary, but my theory goes to hell after that.

"Assume" the nominal audio impedance is 10 times the DC resistance.

So you have small variations around 200 ohms, 3K, and 1.5K.

> like to make a tube mic pre

1-4 input, 2-9 output, -may- be a 1:4 step-up. Which will work reasonably low-noise from mike into a triode grid. Altho I suspect this comes from early transistor work. If it is, indeed, a mike input.

Thanks for your help guys, pin 7 seems to be open to everything. I put 1 volt of 1khz tone into pins 1-4 and got about 4 volts out of 2-9. Pin 9 is connected to the can. So would this make the transformer a 1:4 as PRR suggested?

David

joe-electro said:

Gimme a break...

RuudNL said:

Here are some ohms reading I took

Click to expand...

So now you have magnetized the core of the transformer...

Click to expand...

Click to expand...

Yeah, I'm so sick of that non-sense.  Maybe some crappy Euro iron, but not any American stuff I've ever seen.  If the German and Brit stuff goes funky from that, there's something wrong with it in the first place. 

show us a picture, if you can.   Is this a mounted or a plug-in variety?  I'm assuming plug-in from the part #.

2 and 8 get mis read on xfmr plates a lot?
or is this an octal plug in out of an SS mixer?
there is talk on the forum of this transformer, i even might have taken one apart, but where?

do a search, there is something in the "one bottle" threazd, but i could not find it in the 33 pages

that is pobably a small utc input for a rca ba type transitor amp, so prr got it right.
is it lite gray and 1/4 the size of a fidel castro cigar?


i guessed pin 7, it is the core.

here is rev 2, see if this makes more sense.

you may have a broken connection at the header plate on pin 2.

CJ, it is indeed grey has nine pins and is a plug in type unit. 



Thanks guys!

Pretty sure that's the one found on some later SS PA gear.  935180 is the other RCA #.