## [TechAssist] Re: Sears antique radio, transformer problem

• From: "Christopher Barnak" <cbarnak@xxxxxxxxxxxxx>
• To: <techassist@xxxxxxxxxxxxx>
• Date: Wed, 11 Jan 2006 07:48:57 -0500

```Apply the 1000 hz signal through a small value rheostat.
Measure the signal the junction of the transformer and the rheostat.
Adjust the rheostat until the signal is =BD the applied signal.
Remove the rheostat and measure it's resistance. That is the impedance =
of=20
the transformer.=20

Chris Barnak
Norfolk Public Schools

>>> alg@xxxxxxxxxxx 01/10/06 10:51 PM >>>
If you really want to find the impeadance use a 1000 hz signal connected=20=

to the winding and use voltage/current to calculate.

Al G

J Silverman wrote:
> Not ohm meter ohms - impedance ohms! Impedance ohms are not easy to =
measure.
> Easiest way is to look it up in the transformer manufacturers catalog. =
Also
> the transformer has to have enough iron to handle the DC current without
> saturating. It needs big wire to have low ohm meter ohms in order to be
> efficient and send the power to the speaker instead of burning it up in =
the
> transformer.
> Jerry Silverman Greentron Inc
> Mail to: greentron@xxxxxxx=20
> 4 Newland Ave Greenville SC
> 29609                864 232 3889
> ----- Original Message -----
> From: "KENNETH BARNES" <KENNYB928@xxxxxxx>
> To: <techassist@xxxxxxxxxxxxx>
> Sent: Monday, January 09, 2006 5:22 PM
> Subject: [TechAssist] Re: Sears antique radio, transformer problem
>=20
>=20
>=20
>>  Russ:  Thanks for your reply.  I hooked another transformer in circuit =
-
>=20
> primary reads 175 ohms, secondary .7 ohms.  Speaker doesn't give good =
sound
> as you said.  Bad transf. is about 3 times larger than the one I subbed =
for
> and iron core is much larger in the bad transf.     Any ideas?    Thanks
> again.   Kenny
>=20
>>  ----- Original Message -----
>>  From: Hoyt's TV<mailto:hoytstv@xxxxxxxxxxx>
>>  To: techassist@xxxxxxxxxxxxx<mailto:techassist@xxxxxxxxxxxxx>
>>  Sent: Tuesday, January 03, 2006 2:12 PM
>>  Subject: [TechAssist] Re: Sears antique radio, transformer problem
>>
>>  You can figure it out by the type of output tube they both fit. Look
>=20
> them up
>=20
>>  in an RCA tube manual. I believe will tell you the output impedance =
for
>=20
> the
>=20
>>  tubes. Tubes weren't too fussy though, I think you could get by with
>=20
> most
>=20
>>  any output transformer for a radio of similar type. Likewise the tube
>=20
> won't
>=20
>>  care too much about using a 4 ohm speaker with an 8 ohm transformer.
>=20
> However
>=20
>>  your audiophile customer may go ballistic when those 25kc notes that
>=20
> he's
>=20
>>  accustomed to hearing crystal clear, become a little distorted.
>>
>>
>>  Russ Hoyt
>>  Hoyt's TV
>>  Exeter, NH
>>
>>
>>  ----- Original Message -----
>>  From: "KENNETH BARNES" <KENNYB928@xxxxxxx<mailto:KENNYB928@xxxxxxx>>
>>  To: "techassist"
>=20
> <techassist@xxxxxxxxxxxxx<mailto:techassist@xxxxxxxxxxxxx>>
>=20
>>  Sent: Tuesday, January 03, 2006 12:07 PM
>>  Subject: [TechAssist] Re: Sears antique radio, transformer problem
>>
>>
>>  > Sears antique radio - Question:  A transformer mounted on the =
speaker
>=20
> is
>=20
>>  > open on the primary.  The secondary winding on the transformer is .5
>=20
> ohms.
>=20
>>  > The B+ feeding the transformer primary is 90 volts.  The speaker is
>=20
> 3.6
>=20
>>  > ohms.  I have a good transf. from another speaker which is 8 ohms, =
the
>>  > secondary winding is .7 ohms, the primary winding is 175 ohms.  Can =
I
>=20
> use
>=20
>>  > this transformer in place of the bad one?     TIA            Kenny
>>  > Kenny Barnes TV
>>  > 928 S. Marshall St.
>>  > Boone IA 50036
>>  > 515 432 5250
>>  >
>=20
> KENNYB928@xxxxxxx<mailto:KENNYB928@xxxxxxx<mailto:KENNYB928@xxxxxxx<mailt=
o:K
> ENNYB928@xxxxxxx>>
>=20
>>  >
>>
>=20
>=20
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