Need help interpreting the results of RG Keen's germanium transistor tester

[Henry89789]

I put one of these transistor testors together on a breadboard . It seems to be connected properly and it works (at least it gives readings for each portion of the test). My 2.47k resistor reads 2.4 on the meter and the 2.2m reads 2.1M. I used a Boss PSA power supply.

I tested a few AC125VI with results as follows:

    Voltage        press switch
1.  1.20              9.36
2.   .70               9.36
3.  .68               9.37
4.   .85              9.37

I have read the instructions on using the tester but I am not sure how to interpret the results. Do you have to do math for each test? Also I think I am doing something wrong because the results after pressing the switch are all the same.  Please help. Thanks.

[Henry89789]

In regard to the first reading:   1.20.  If one mA of leakage would result in a reading of 2.4  then this has .5 mA of leakage. Is that right?

second reading:   .70.   About a little less than 1/3 less than one mA . So the leakage would be about .3 mA.   Is this correct?

In regard to the gain, I don't understand how to figure that out given the consistent 9.36 readings after pressing the switch. I have read that article over and over and it seems to need a gain to figure out the gain. Don't understand that. Again please help me figure this out. Thanks.

[Arcane Analog]

Your tester has issues. Fix it first. You are reading the battery's straight voltage on the 9.XX readings.

[Henry89789]

Arcane:

thanks. Yeah I had the wrong value resistors. I put the right resistors and here's what I got.

             voltage                          press switch                   Hfe          Lkg
1.            .83                               1.66                            145          .33

2.            .89                               2.05                            116          .36

3.            .82                               1.60                            139         .35

4.          1.30                              2.35                             104         .52

Are my calculations correct?   Thanks.

[Arcane Analog]

I answered this exact question a few weeks ago. I provided random numbers and used them as an example. You should use the search function as this forum is full of information.

First, if using the RG method, you must regulate your power supply to an even 9V. A simple pot works well for that as it can dump the excess juice from your adapter or battery and make it easy to hit the 9V that RG specifies - along with the 2.472K and 2.2M resistors.

Measure your transistor for leakage with the tester and the old multimeter:
0.345V

As a side note, a lot of people use uA to note/discuss leakage: uA = microamps - mA = milliamps - 1000 uA = 1 mA
0.345V divided by 0.002472 = ~139.6uA of leakage

Flip Switch for the 'total' gain reading:
1.666V

So take the 'total' gain reading and subtract the leakage:
1.666 - 0.345 = 1.321V

Take that number and multiply by 100 for your 'true' gain.
1.321 x 100 = 132

Hope that helps.

[Henry89789]

Thanks. I found that thread - How to Calculate Transistor Leakage? - doing a search of your name. That RG Keen article seems to assume the knowledge of an electronic engineer on the part of the reader. It needs a serious "interpretive" flow chart type addendum for lay persons. Now I'm gonna study your answer here and that thread ....

[Arcane Analog]

You can also click on the links provided in quotes. There are links in all of the bold prtions starting with "Quote from:" which bring you to the thread/quote.