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Biasing Problems


 
6/5/1999 4:40 PM
Warren
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Biasing Problems
Hey all,  
 
I'm trying to bias using the transformer shunt method, but I think I'm doing something wrong here.  
 
I'm going from Pin 3 to the center tap, but I'm not getting any reading on the meter. Do I have to un-solder the center tap from ground to get it to read or am I doing something else wrong? I've got the meter set to the 200mA DC setting, red probe on the pin, black on the ground.  
 
Any help would be greatly apprectiated.
 
6/5/1999 7:37 PM
Dave S.
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Warren:  
 
You don't have to disconnect the wire from the lug. It sounds as if you might have a blown fuse in you meter or your probes to your meter is not connected right.  
 
What type of meter are you using?  
 
Dave S.
 
 
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6/5/1999 7:42 PM
Dave S.
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Warren:  
 
One more thing. You was refering to the center tap as ground. The center tap should be connect to the B+ rail. If you connect your current meter from pin 3 to ground it would be a short....Blown fuse!  
 
Best Wishes  
Dave S.
 
6/6/1999 9:27 AM
Tom Lennon
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Warren,  
I just did the same measurement on a Princeton silverface. The first thing I did wrong was not hook up my meter leads correctly ( at the meter). I had to move the red lead over to the mA position to get a reading. The next thing I did wrong was to go from pin 3 to ground as in a plate voltage measurement. That blew the fuse in my meter.  
The red lead goes to the center tap and the black lead goes to pin 3, ( red lead, red center tap wire) then I started to get the readings. I still managed to touch something else in the vicinity of pin 3 and blew another fuse so I put shrink tubing on all but just the very tip of my leads. One other precaution I took was to make the center tap connection last and remove it first after taking the measurement since it was easier to place the lead there and any inadvertant contacts w/ the black lead wouldn't complete a circuit.  
Tom Lennon
 
6/6/1999 1:58 PM
Warren
email

You know,  
 
I think it would work better if I was using the center tap on the output transformer rather than the power transformer.  
 
Now I just gotta dig up some more fuses and its on to the next lesson...  
 
Thanks for all the help,  
 
Warren
 
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