Electronic – Identify Zener diode

diodesidentificationzener

I need two 5.1V Zener diodes for a small project.

My knowledge in electrical engineering are severely limited, but have some boxes with components that I have taken from various electronic equipment. Among these are a few, what I believe to be, Zener diodes. Looks like this:

Old picture: http://i.stack.imgur.com/91zpw.jpg (from web)

Edit: Here is a picture of the stash. The ones at the bottom are the “otherwise colored as described below.” (My hand is a bit more steady then what the lines would suggest :P)

stash

Inscription on the ones I have are:

  3 |   2  |  1 |  1  |  1 |   1  | 1 | <- How many I have
----+------+----+-----+----+------+---+
 48 | I N4 | 56 | 13Z | 13 | 5.6Y | 9 |
 H  | I 48 | B3 |     | B2 |      | 1 | {- Inscription
    |   ST |    |     |    |      | C |

I also have some that looks similar to the one in the picture, but they have blue instead of black "paint" as well as a silver line on the end with the paint (inside the glass). Of those I have 12 without markings and three with the marking: T5. Not sure if these are Zener diodes.

Question is if I am in luck and any of the ones I have can be used.

Anyhow it would also be nice to know if those inscriptions bear any meaning one can decipher.

Schematic:

enter image description here

Best Answer

Unless you get lucky and find a whole part number (as in the 1N4148), you're better off measuring. Get a 20 V supply or so and a 2 kΩ resistor. Most diodes (other than LEDs, but that's not the issue here) aren't going to be damaged with either 20 V reverse voltage or 10 mA thru them either way.

Connect the 20 V with the 2 kΩ in series to each diode and measure the voltage. With the + to the anode and - to the cathode (striped end), all the diodes should measure around 700-800 mV. If a diode measures 20 V that way, then it's blown. If it measures about half that, then it's a Schottky and not a zener.

Now flip the diode around and measure the voltage again. This will show you the Zener voltage. Put them in bins accordingly. If a diode measures the full 20 V, then it's either not a Zener (like the 1N4148), or its Zener voltage exceeds 20 V (unlikely).

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