How to Read Zener Diode Code


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Many technicians are confused on how to really read a zener diode code. There are many types of code number indicated on it's body. The look and shape of a zener diode sometimescan be mistaken to be a normal signal diode. To differentiate it, is by looking at the codenumber on it's body- whether it is a normal diode or zener diode. Thanks to the manufacturers where their main boards are printed with the word ‘ZD’ which referred to zener diode and ‘D’ means a diode.

However, from my experienced some printed circuit board the marking of ‘D’ also can represent zener diode. This will misled a technician into believing a zener diode is actually a diode. We as a technician or engineer must know or be sensitive about the marking. The only way to find out is by referring the code number printed on the component's body from a semiconductor data book. Without data book it is quite difficult to know the actual zener diode voltage. If you do not have the data book you may go to google search engine and type the following code and hope you can find the answer there! A wrong substitution of zener diode may caused your equipment to malfunction and sometimes will even blow your equipment. Time and money are loss due to that we lack of knowledge of identify the right zener diode voltage. If you are unable to identify the code, do not worry as this newsletter are here to guide you to successfully on how to read the zener diode code.

5.1=5.1Volt zener diode

5V1=5.1Volt zener diode

12= 12 Volt zener diode

12V= 12 Volt zener diode



Note: There is also part number such as BZVXXXXX where you have to find it from ECG SEMICONDUCTOR BOOK.

1N4746= 18 Volt 1 watt zener diode (refer to ECG PHILIPS SEMICONDUCTORS MASTER REPLACEMENT GUIDE)

6C2=6.2 Volt zener diode. (If you look at the zener diode code it is written as 6C2 READING FROM TOP TO BOTTOM) Don't read from bottom to top otherwise the value you get is 2C6 which you cannot find from data book!

I believe many will ask how do I get the voltage for the code of 6C2. Still refer to ECG book, you have to search for HZ part number. That's mean instead of finding 6C2, search for HZ6C2 and you will get the answer! The lowest zener voltage that I came across was 2.4 volt and the highest was 200 Volt 5 watt.

Conclusion- Be alert when checking the part number of a zener diode. Don't always assume that a small signal diode is always a zener diode. Carefully observe the marking on the main board and read the zener diode part number refer to the semiconductor book, preferably ECG SEMICONDUCTOR DATA BOOK which you can get from your local electronic distributor. With this knowledge in mind, you will be successfully find the right voltage of a zener diode.

Jestine Yong is a electronic repairer and writer. For more information on electronic repair please visit his website at


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