[R-390] Re: UTC 68819 xfmr

Fri, 13 Dec 2002 18:08:39 -0800

Hi all,  thanks for the suggestions on the transformer.  It was id'd by one
member as 150/75000 ohms,  a transformer used in RC 47a & c (probably from the
40's or late 30's)  same as UTC 46779.  After first suggestion to do so,   I
measured it as 187 ohm /75000 ohm  so am satisfied I know what it is to the
degree I need to know (still curious why the voltage ratio didn't give the exact
impedance ratio though).  Since my first query,  I dug out three more of these
in my pile plus some other interesting input transformers including some WE
transformers and some signal corp small xfmrs so I have a number to experiment
with and explore.  thanks to all for providing what I needed.  Dan

Dave and Sharon Maples wrote:

> Drew: That's an excellent technique.  I think in this case I'd be inclined
> to apply 6 VAC to the 75,000 ohm winding, and measure the other winding.
> That way the resultant will be in the millivolt range, and the transformer
> won't pull any serious current...
>
> Dave WB4FUR
>
> -----Original Message-----
> From: [email protected] [mailto:[email protected]]On
> Behalf Of Drew Papanek
> Sent: Friday, December 13, 2002 1:12 PM
> To: [email protected]
> Subject: [R-390] Re: UTC 68819 xfmr
>
> Dan,
>
> You can easily determine the unknown impedance from voltage measurements.
> Apply an AC signal of appropriate frequency  to the known winding (110 VAC
> 60 Hz works well for a typical high impedance audio transformer winding).
> Measure AC voltage on secondary.  Divide this by primary voltage and square
> the result.  This gives you the impedance ratio from which you calculate the
> secondary impedance.   I have used 6.3 VAC on a low impedance winding and
> measured the resultant on the high impedance winding.  Don't apply high
> voltage to a low impedance winding or you'll let the smoke out.
>
> Drew
>
> >Date: Thu, 12 Dec 2002 15:35:49 -0800
> >From: Dan Merz <[email protected]>
> >Reply-To: [email protected]
> >To: R-390 List <[email protected]>
> >Subject: [R-390] UTC 68819 xfmr?
> >
> >Hi,  does anyone happen to know the prim/sec impedance of a UTC 68819
> >transformer,  Army #2Z9986-2;  the box is marked  ?50-ohm to 75,000 ohm
> >but not legible enough to make out the primary.  It's small unit about 3
> >inch high,  thanks,  Dan.
>
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