SissySIT

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#282
juanitox said:
i have mesured my pair of TH51s and at 18V VDS i have one at 850ma for -1.92V gate bias and the other at 950ma

is it ok for the project ? 😕
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Unfortunately, ZM is "off the grid" (see post #262) but if you look at post #81, he says that anything between "-1 to -3V6 is adequate for SissySIT circuit".

Your measurements are slightly below the -1V, but close. ZM's post says that he will be away until Saturday, so hopefully he will be able to answer your question then.
 
#283
YES ang NO？

Ben Mah said:
Unfortunately, ZM is "off the grid" (see post #262) but if you look at post #81, he says that anything between "-1 to -3V6 is adequate for SissySIT circuit".

Your measurements are slightly below the -1V, but close. ZM's post says that he will be away until Saturday, so hopefully he will be able to answer your question then.
Click to expand...

Select 10V voltmeter
1 turn the 10V voltmeter with the pot to full 9V

2 now switch on power supply and turn the pot that the voltage goes down from 9V slowly

3 watch the ampere meter, when see 2A, stopp turning the pot and look at the 10V meter what ist the value….maybe 5V or 3V or 2V….or ……the SITs are all very different°

4. you write the value of voltmeter on the SIT or in a list… Or….
 
#284
Sounds right. When power supply is on and pot is to full 9V, current should be 0A. As 9v is reduced, current should increase from 0A, and yes, you write the value of Vgs when I=2A.

There will be different values of Vgs for different SITs. Since the 9V negative terminal is connected to the gate through the pot and 1K resistor and the positive terminal is connected to ground, Vgs is actually considered to be a negative value.
 
#285
Ben Mah said:
Unfortunately, ZM is "off the grid" (see post #262) but if you look at post #81, he says that anything between "-1 to -3V6 is adequate for SissySIT circuit".

Your measurements are slightly below the -1V, but close. ZM's post says that he will be away until Saturday, so hopefully he will be able to answer your question then.
Click to expand...

i have made new try with a stronger power supply and i get with -2.4V gate bias
1.83A with the first and 1.93A with the other so mine are not really matched
:whazzat:
 
#286
You do not have two DMM (digital multi meter)!at your working place instead of the simple volt and ampere meters?


pras1170 said:
This is the material I prepared (the experiment has not officially started yet, because the voltmeter has a problem, it stays there all the time and does not return to zero. I will buy another voltmeter tomorrow to replace it) : according to # 81
Everybody take a look at it for me, right?
I have not turned on the power, everything is imitation state, has not officially plugged in power
Let's take a look. Is that right?

5 a current meter
9 v battery
10 v voltage meter

1 w 1 k resistor
10 k locator
24 v power supply
24V dc fan
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#287
Ben Mah said:
Watanabetomoaki has replied with an answer:

"The written numbers on them means Id (A), at Vds=25V Vgs=-1V aroun 25 degreeC."
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As I mentioned in an earlier post, I have two THF-51Ss from watanabetomoaki that have 2.5 written on them. When I tested them at 24V and 1.8A, I measured Vgs of -4.46V and -3.54V respectively.

I just measured the one with Vgs = -4.46V again but with Vds 25V and Id = 2.5A to try to mimic watanabetomoaki's parameters. The result was Vgs= -4.28V.

Lowering Vgs even more raises Id even more, so I cannot replicate the Vds=25V, Vgs=-1V, Id=2.5A.

I wonder about the capacity of his power supply? Can it produce more than 2.5A? If it cannot, that is probably a good thing as testing at Vgs=-1V does not seem like a safe way to grade the devices.

I am in discussions with him and I have mentioned that testing at Vgs = -1V may not be a good thing.
 
#288
juanitox said:
i have made new try with a stronger power supply and i get with -2.4V gate bias
1.83A with the first and 1.93A with the other so mine are not really matched
:whazzat:
Click to expand...

I should learn to read properly. I misread your earlier post that mentioned 850ma and 950ma, and 1.92V. In my mind I saw 850mV and 950mV, and 1.92A, and thus my erroneous comment regarding them being close to -1V.

Old age is scrambling my brain and eyesight.
 
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#289
generg said:
You do not have two DMM (digital multi meter)!at your working place instead of the simple volt and ampere meters?
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This experiment was taken out of my shop by me, and I worked in the shop during the day, with less comprehensive tools

We'll do what we said yesterday, test it, and then publish the results

I don't have time to take it out and test it. I have time in the afternoon
 
#291
Please take a look, I am right? Please take a look at the test process;
THF-51T OLD USED
THF-51S NEW NOS 2SK182ES NEW NOS
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#295
Zen Mod said:
for THF51-S , body is drain ( no need for isolation for test , just keep heatsink electrically from other voltage potentials , other than + rail), fat protruding pin is source,while thin protruding pin is gate



again , any power N channel JFet , having ebough cojones , and having gate voltage in range of -1 to -3V6 is adequate for SissySIT circuit

if you sort your P channel mosfets , and use those with highish gate voltage (for -19 to -25V and Iq 1A8 to 2A) , in area of -4V5 , JFet can have even -4V gate voltage for intended conditions
have more questions , shoot
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Copy the language of Zen Mod

And having gate voltage in range of -1 to -3V6 is adequate for SissySIT circuit

Did I do that?
 
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