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  #11  
Old 09-15-2013, 07:07 AM
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Did the math. At about 380 ua, a GFCI would not detect the fault.
My bad.
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  #12  
Old 09-15-2013, 04:59 PM
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First off the wrong symbol is used, Earth symbol instead of chassis.
It appears that the chassis is the common reference but on the DC supply the C.T. the common is raised above chassis by 3 reference/bias resistors (77)?.
Max.
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Old 09-15-2013, 06:12 PM
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True, the center tap of the high voltage winding is raised above ground by 3 resistors which apparently make some DC bias voltages, but that means nothing about how to apply the power cord.
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Old 09-15-2013, 06:26 PM
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Quote:
Originally Posted by #12 View Post
but that means nothing about how to apply the power cord.
True, Just an aside comment.
I never meant to muddy the water!
To OP, you may want to check or replace the two electrolytics either side of the DC PI filter, ones of that age tend to be a cause of failure, and take out the rectifier tube.
Max.
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Old 09-15-2013, 10:05 PM
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and take out the rectifier tube.
Max.
and THEY (the capacitors) take out the rectifier tube.
Just clearing up your phrasing.
(It sounded like you were telling HIM to take out the rectifier tube.)
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Old 09-16-2013, 03:46 AM
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Quote:
Originally Posted by MaxHeadRoom View Post
First off the wrong symbol is used, Earth symbol instead of chassis.
It appears that the chassis is the common reference but on the DC supply the C.T. the common is raised above chassis by 3 reference/bias resistors (77)?.
Max.
It wasn't the wrong symbol back then.

The symbol used in this schematic was commonly used for both types of "Earth",as well as for a real "earth" stake used with an external antenna.

It was usually obvious which was meant by the context.

The resistors between the transformer centre tap & chassis were for "back bias" which was used to simplify bias circuitry.

The chassis is several volts +ve w.r.t. the centre tap,so connecting the cathodes to chassis & returning the grids to various points along the voltage divider is the same as providing a separate -ve grid supply,but cheaper.

This is fairly easy to see in the audio stages,but is a bit messy in the IF stages with the additional circuitry for AGC.
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  #17  
Old 09-16-2013, 03:52 AM
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It wasn't the wrong symbol back then.
.
I wonder what the excuse is now though for current literature that makes the error?
Max.
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  #18  
Old 09-16-2013, 03:58 AM
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It is still usually obvious from the context .
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  #19  
Old 09-16-2013, 02:42 PM
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It is still usually obvious from the context .
??????????
You mean I have to make assumptions?
Max.
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Last edited by MaxHeadRoom; 09-16-2013 at 03:03 PM.
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  #20  
Old 09-17-2013, 03:47 PM
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??????????
You mean I have to make assumptions?
Max.
Yes,Max!
I stand my ground on this!
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