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 S.T.C Console Radiogram
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 Return to top of page · Post #: 1 · Written at 10:32:19 AM on 1 October 2020.
Bowler's Gravatar
 Location: Bongaree, QLD
 Member since 26 October 2018
 Member #: 2308
 Postcount: 39

Good morning all, I have a chasis from an STC radiogram model 8471. It is a push pull arrangement on the output. Could someone explain the output transformer workings. It appears that both transformers are wound on the one core. The circuit is available on the Kevin Chant site.Bowler


 
 Return to top of page · Post #: 2 · Written at 11:31:18 AM on 1 October 2020.
Gandhn's Gravatar
 Location: Cameron Park, NSW
 Member since 5 November 2010
 Member #: 770
 Postcount: 350

The specifications on Kevin's site refers to the two output transformers (in parallel), both mounted on the chassis.

What leads you to the thought they are wound on the same core? A photo of the chassis top should help.

Harold


 
 Return to top of page · Post #: 3 · Written at 6:52:31 AM on 2 October 2020.
Fred Lever's Gravatar
 Location: Toongabbie, NSW
 Member since 19 November 2015
 Member #: 1828
 Postcount: 915

Hi Bowler, I have one of these chassis.
Featured in a special projects thread on this site built into a big cabinet as a project
.
The chassis had TWO output transformers, one large one above the chassis to drive the main 12" speaker and a little unit mounted underneath to drive the tweeters.,
In mine both OPTs were faulty, open circuit.
I rewound the main one and coupled the tweeters from the main one through a 4.7μF cap.

Fred.


 
 Return to top of page · Post #: 4 · Written at 9:08:38 AM on 2 October 2020.
Bowler's Gravatar
 Location: Bongaree, QLD
 Member since 26 October 2018
 Member #: 2308
 Postcount: 39

Hi Fred and Harold, many thanks for your replies. The whole thing is making much more sense to me now. Bowler


 
 Return to top of page · Post #: 5 · Written at 10:25:46 AM on 8 October 2020.
Bowler's Gravatar
 Location: Bongaree, QLD
 Member since 26 October 2018
 Member #: 2308
 Postcount: 39

Good Morning Fred, Thanks for the previous advice on the stc 8471. Could you tell me what the 6.3 volt outlet was used for. There is a 100 ohm 10 watt variable resistor across the heater winding associated with this outlet. Bowler


 
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