Great example of DIY custom test equipment! I kinda really love (Transistor Outline-92) TO-92/TO-18 "thru-hole" transistors given the lack of standards in Surface Mount SMT footprint pin numbering randomness.
Built one many moons ago, using a small well used transformer that had a 100V secondary, and a 6V secondary as well. Half wave rectified both, to get 150ish V as compliance, and used a simple constant current source with a LED, and a MJE13003 and a 2N2222A as pass elements, collector of the 2N222A being connected to the 9V supply that ran the constant current circuit, and a 1M resistor across the output to provide a discharge path. As I had often enough to test 75V zener diodes the ability to go to 150V was useful, though it could bite. the high voltage used a salvaged capacitor, IIRC 22uF 250V, and the low voltage a 1000uF 25V salvaged one as well, with the reference being a red LED and 2 1N4148 diodes in series, and a 150R resistor to set the 10mA current, though it really could not supply that for long periods, as the transistor was likely to overheat, being on a smallish heatsink. But as a quick and simple tester perfect, and it also was well capable of testing transistors for breakdown as well.
Btw: You should make one with a sawtooth generator and a voltage controlled current source to use for making diode plots on x/y oscilloscopes. Not everyone has those nice fancy curve plotters you have 😀
A few months ago I had to test zener from. Mac SE/30 power supply. They were around 30-35V. Rigged up my variable 50v supply and one resistor in series and a DVM to measure the voltages. By varying my supply voltage I was able to vary the current, although not as elegant as IMSAI Guys circuit it was enough to work out what value the zener was so we could test replacements. The part on the board didn’t give us any clues to its value. I was surprised how much voltage variation you get depending on the current and also the variance between two identical parts purchased together. Nearly 2-3V difference at that voltage.
Not sure why you didn’t just put 2 jumpers for added current. One for +5mA and the other for +10mA and the base load of 5mA. You could get 5, 10, 15 and 20mA options that way with two jumpers instead of 3 (or was it 4?).
There are small circuit board switches called DIP switches. You could use one of these (very low cost) switches to change the current. The zener impedance is another factor that needs to be measured. This is derived from a small change voltage with a change in current. Ideally the impedance should be zero but in real zeners it can be very bad!
Now I see why you have used a manually current programming cascade. The recommended test currents of Zener diodes differ allready for the same Zener voltage. But I would use a progressive current programmer like 2, 5, 10, 20 mA, also usable in combination, to get more settings in a broader current range. I think the precision of the resistors is not so important. You don't need 0.1%. The standard of 1% is enough. 5% would be ok as well.
Now that you've disassembled that weird connector you're going to find out tomorrow that you need it for something.
Of course :-)
It is also possible to order these copper areas gold plated.
A zener symbol whould be better but I guess it is up to the builder how it should look. Thanks for great videos.
Yep. I agree. A zener symbol would seem more intuitive.
Great example of DIY custom test equipment!
I kinda really love (Transistor Outline-92) TO-92/TO-18 "thru-hole" transistors given the lack of standards in Surface Mount SMT footprint pin numbering randomness.
Actually pretty cool the way you see the supply voltage and then the zener voltage 👍
Built one many moons ago, using a small well used transformer that had a 100V secondary, and a 6V secondary as well. Half wave rectified both, to get 150ish V as compliance, and used a simple constant current source with a LED, and a MJE13003 and a 2N2222A as pass elements, collector of the 2N222A being connected to the 9V supply that ran the constant current circuit, and a 1M resistor across the output to provide a discharge path. As I had often enough to test 75V zener diodes the ability to go to 150V was useful, though it could bite. the high voltage used a salvaged capacitor, IIRC 22uF 250V, and the low voltage a 1000uF 25V salvaged one as well, with the reference being a red LED and 2 1N4148 diodes in series, and a 150R resistor to set the 10mA current, though it really could not supply that for long periods, as the transistor was likely to overheat, being on a smallish heatsink. But as a quick and simple tester perfect, and it also was well capable of testing transistors for breakdown as well.
Keep your jumpers connected to 1 of the pins when they are not being used so you can always find them.
Good advice 👍
Xmas present ... Ho Ho Ho, IMSAI Elf
nice project, at work we used two smooth alligator clips soldered up on a protoboard to sort diodes for Vf 👍👍
Btw: You should make one with a sawtooth generator and a voltage controlled current source to use for making diode plots on x/y oscilloscopes.
Not everyone has those nice fancy curve plotters you have 😀
A few months ago I had to test zener from. Mac SE/30 power supply. They were around 30-35V. Rigged up my variable 50v supply and one resistor in series and a DVM to measure the voltages. By varying my supply voltage I was able to vary the current, although not as elegant as IMSAI Guys circuit it was enough to work out what value the zener was so we could test replacements. The part on the board didn’t give us any clues to its value. I was surprised how much voltage variation you get depending on the current and also the variance between two identical parts purchased together. Nearly 2-3V difference at that voltage.
Not sure why you didn’t just put 2 jumpers for added current. One for +5mA and the other for +10mA and the base load of 5mA. You could get 5, 10, 15 and 20mA options that way with two jumpers instead of 3 (or was it 4?).
There are small circuit board switches called DIP switches. You could use one of these (very low cost) switches to change the current. The zener impedance is another factor that needs to be measured. This is derived from a small change voltage with a change in current. Ideally the impedance should be zero but in real zeners it can be very bad!
DIP switches are nice but have one drawback: toggle count measured in a few hundreds.
@@LubosMedovarsky Good enough! By the time I test that many zener diodes I can swap out the switch.
Now I see why you have used a manually current programming cascade. The recommended test currents of Zener diodes differ allready for the same Zener voltage. But I would use a progressive current programmer like 2, 5, 10, 20 mA, also usable in combination, to get more settings in a broader current range. I think the precision of the resistors is not so important. You don't need 0.1%. The standard of 1% is enough. 5% would be ok as well.
3 holes instead of 4 was just to trigger my OCD right?
Zener diode tester 2.0 could be a Arduino project?
Not KIS. Why not use PS with adjustable current and voltage limiting?
Great piece of test kit !.....cheers.
👍👍👍👍👍