Had had spare time to try again...
First I learned, fet's can be out of order while measuring ok for IDSS check. The defective device showed 900k of resistance between gate and source, new ones are beyond the capabilities of measuring. Still those defective device showed their once stated IDSS when testing. The offset between the gates of a pair was around 0.3V, with new ones 0.00V
But, the current source (which I stuffed with new devices just to be on the safe side) now draws excessive power (around 36mA)
There is no voltage drop over Rload, something still tricks me here...
Rüdiger
First I learned, fet's can be out of order while measuring ok for IDSS check. The defective device showed 900k of resistance between gate and source, new ones are beyond the capabilities of measuring. Still those defective device showed their once stated IDSS when testing. The offset between the gates of a pair was around 0.3V, with new ones 0.00V
But, the current source (which I stuffed with new devices just to be on the safe side) now draws excessive power (around 36mA)
There is no voltage drop over Rload, something still tricks me here...
Rüdiger
Fred, you worry too much. Look at the construction of a 2SK146. Does this make sense to you? You will find that two 2SK147's are put together face to face. Guess what? One has to be upside down. Still they work, still they track. Why worry about it? The same goes for the 2SK170, and many other devices.
Hi,
Are you sure nothing's operating at Znil? Sorry, I didn't do the maths but if you experience excessive current then it follows that something is conducting that is'nt suppsed to.
Check it,)
Are you sure nothing's operating at Znil? Sorry, I didn't do the maths but if you experience excessive current then it follows that something is conducting that is'nt suppsed to.
Check it,)
I hit the wrong one again?
"Fred, you worry too much. Look at the construction of a 2SK146. Does this make sense to you? You will find that two 2SK147's are put together face to face. Guess what? One has to be upside down.* Still they work, still they track. Why worry about it? The same goes for the 2SK170, and many other devices."
John I was trying to provoke the other JC a little. I did not think the Toshibas were asymmetrical as most jfets are which why I included the examples and the die diagram of the second source for the K147. I thought those were sufficient clues to indicate I was having a little fun with Mr. Carr..... Sorry you got caught in the crossfire of the pie fight. While you're here though, what should one do with that center pin on the K389 and J109 and when is actually all right to remove that tag on the mattress that reads Do Not Remove?
Fred
*Actuallly it not upside down but is rotated 180 degrees about the axis extending in the direction of the legs. You are right about the K146 indicates the two drain and two source legs are adjacent.
"Fred, you worry too much. Look at the construction of a 2SK146. Does this make sense to you? You will find that two 2SK147's are put together face to face. Guess what? One has to be upside down.* Still they work, still they track. Why worry about it? The same goes for the 2SK170, and many other devices."
John I was trying to provoke the other JC a little. I did not think the Toshibas were asymmetrical as most jfets are which why I included the examples and the die diagram of the second source for the K147. I thought those were sufficient clues to indicate I was having a little fun with Mr. Carr..... Sorry you got caught in the crossfire of the pie fight. While you're here though, what should one do with that center pin on the K389 and J109 and when is actually all right to remove that tag on the mattress that reads Do Not Remove?
Fred
*Actuallly it not upside down but is rotated 180 degrees about the axis extending in the direction of the legs. You are right about the K146 indicates the two drain and two source legs are adjacent.
That has been quiet true
I made a silly mistake
I still have to figure out why the whole unit distorts lower frequencies while it is perfectly without noise and measures ok. Seems to be some weird interaction between fet-stage and output stage.
Apart from that, i would really like to know, why a defective fet can pass through the correct amount of current?
Rüdiger
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