Transformer color code quandry
 

I've been going through some transformers to see what to keep and what
to lighten the load, so to speak. I found one that I can't quite figure
out. The thing is about the size we'd see on a 60's TV set. Nice piece
of iron and useful. The issue is this: There are four sets of windings.
The B+ set is easy, color and resistance are consistent with the
winding. There are 3 other windings. One is identifiable as the 5v
filament winding, another as the 6.3v winding, leaving what I believe is
the primary (blinding glimpse of the obvious?). There are 3 wires left
over for (what I believe is the primary. One black lead that pairs with
another dark color wire. They ohm out as would a primary winding; that
is, low resistance but an obvious inductive reactance. The bug is that
there's yet a third wire associated with this pair and the resistance is
several hundreds of ohms in relation to the other two. Any ideas? It
can't be a CT, of course, and its way too high resistance to be a 220v
tap. Also, the wire size of the "primary" is #16 and this outrider is
maybe #18 or #20. I didn't just fall off the turnip wagon but this is a
poser?

de Jeep/K3HVG



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Transformer color code quandry
 

K3HVG wrote:
I've been going through some transformers to see what to keep and what
to lighten the load, so to speak. I found one that I can't quite figure
out. The thing is about the size we'd see on a 60's TV set. Nice piece
of iron and useful. The issue is this: There are four sets of windings.
The B+ set is easy, color and resistance are consistent with the
winding. There are 3 other windings. One is identifiable as the 5v
filament winding, another as the 6.3v winding, leaving what I believe is
the primary (blinding glimpse of the obvious?). There are 3 wires left
over for (what I believe is the primary. One black lead that pairs with
another dark color wire. They ohm out as would a primary winding; that
is, low resistance but an obvious inductive reactance. The bug is that
there's yet a third wire associated with this pair and the resistance is
several hundreds of ohms in relation to the other two. Any ideas? It
can't be a CT, of course, and its way too high resistance to be a 220v
tap. Also, the wire size of the "primary" is #16 and this outrider is
maybe #18 or #20. I didn't just fall off the turnip wagon but this is a
poser?

Apply 6.3VAC to the 6.3V winding, from a filament transformer. Now
measure the voltages on the other leads and see what they are.

Yes, the unloaded voltage will be higher than the loaded voltage. Yes,
if you energize the secondary, the measured primary voltage will be
lower than normal since the transformer ratio is set up to account for
resistive losses and you now have the resistive losses PLUS the reverse
of that step-up. The two errors more or less cancel one another out,
and you wind up pretty close to the right value.
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."

Transformer color code quandry
 

On Wed, 18 Feb 2009 19:49:49 -0500, K3HVG wrote:

I've been going through some transformers to see what to keep and what
to lighten the load, so to speak. I found one that I can't quite figure
out. The thing is about the size we'd see on a 60's TV set. Nice piece
of iron and useful. The issue is this: There are four sets of windings.
The B+ set is easy, color and resistance are consistent with the
winding. There are 3 other windings. One is identifiable as the 5v
filament winding, another as the 6.3v winding, leaving what I believe is
the primary (blinding glimpse of the obvious?). There are 3 wires left
over for (what I believe is the primary. One black lead that pairs with
another dark color wire. They ohm out as would a primary winding; that
is, low resistance but an obvious inductive reactance. The bug is that
there's yet a third wire associated with this pair and the resistance is
several hundreds of ohms in relation to the other two. Any ideas? It
can't be a CT, of course, and its way too high resistance to be a 220v
tap. Also, the wire size of the "primary" is #16 and this outrider is
maybe #18 or #20. I didn't just fall off the turnip wagon but this is a
poser?

de Jeep/K3HVG

If you weren't across the continent I'd back my pickup up to your pile,
as a handy place for you to put the rejects...

--
http://www.wescottdesign.com

Transformer color code quandry
 

On Feb 18, 5:49*pm, K3HVG wrote:
I've been going through some transformers to see what to keep and what
to lighten the load, so to speak. *I found one that I can't quite figure
out. *The thing is about the size we'd see on a 60's TV set. *Nice piece
of iron and useful. The issue is this: *There are four sets of windings..
* The B+ set is easy, color and resistance are consistent with the
winding. *There are 3 other windings. *One is identifiable as the 5v
filament winding, another as the 6.3v winding, leaving what I believe is
the primary (blinding glimpse of the obvious?). *There are 3 wires left
over for (what I believe is the primary. *One black lead that pairs with
another dark color wire. *They ohm out as would a primary winding; that
is, low resistance but an obvious inductive reactance. *The bug is that
there's yet a third wire associated with this pair and the resistance is
several hundreds of ohms in relation to the other two. *Any ideas? *It
can't be a CT, of course, and its way too high resistance to be a 220v
tap. *Also, the wire size of the "primary" is #16 and this outrider is
maybe #18 or #20. *I didn't just fall off the turnip wagon but this is a
poser?

de Jeep/K3HVG

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See: http://www.radioremembered.org/xfmr.htm

Transformer color code quandry
 

I appreciate all the comments and have applied them to the issue. I
fired the transformer up and it does function, generally as expected.
The B+ bridge type winding puts out about 350v, unloaded. I expected
the one of the two filament windings (green) to be 5v but they both and
put out over 6.9v unloaded. The green winding puts out a good 6.5v with
a 5v rectifier tube filament wired to it, so it must be a healthy 6.3v
winding, instead. The outrider wire on the primary winding appears to
color code out as a "primary tap", using the link provided by Cmdr.
Buzz. Maybe the extra wire is, indeed, a 220v winding. If I could
remember from whence it came??? Again, thanks to all. de K3HVG



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Transformer color code quandry
 

"K3HVG" wrote in message
...



I appreciate all the comments and have applied them to the issue. I fired
the transformer up and it does function, generally as expected. The B+
bridge type winding puts out about 350v, unloaded. I expected the one of
the two filament windings (green) to be 5v but they both and put out over
6.9v unloaded. The green winding puts out a good 6.5v with a 5v rectifier
tube filament wired to it, so it must be a healthy 6.3v winding, instead.
The outrider wire on the primary winding appears to color code out as a
"primary tap", using the link provided by Cmdr. Buzz. Maybe the extra wire
is, indeed, a 220v winding. If I could remember from whence it came???
Again, thanks to all. de K3HVG



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What voltages are you reading on the "primary tap" when
testing? It should work as an autotransformer to give
some idea if it is indeed a 220 volt winding or 110 volt
tap.

Also, the lighter gauge might make more sense
considering that the primary current would be 50% of
what it would draw on 110 VAC when using the 220VAC
winding.

Pete