How to Read Zener Diode Code

zener diode symbol from Wikipedia.com

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

BZX85C22=22Volt 1 watt zener diode (refer to ECG PHILIPS SEMICONDUCTORS MASTER REPLACEMENT GUIDE)

BZY85C22=22Volt 1/2 watt zener diode (refer to ECG PHILIPS SEMICONDUCTORS MASTER REPLACEMENT GUIDE)

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 a writer and if you want to become a professional in testing electronic components please visit his website at http://www.TestingElectronicComponents.com

What is EEPROM?

EEPROM stands for Electrical Erasable Programmable Read Only Memory and also referred to as E²PROM. As the name suggest, an EEPROM can be both erased and programmed with electrical pulses. Since it can be both electrically written into and electrically erased, the EEPROM can be rapidly programmed and erased in circuit for reprogramming without removing them from the circuit board.

EEPROM is also called a non-volatile memory because when power is turned off the stored data in the EEPROM will not be erased or intact. New EEPROM have no data in it and usually have to program with a programmer before it can be use. Information stored in this type of memory can be retained for many years without a steady power supply.

What is the function of EEPROM? EEPROMs are used to store user programmable information such as: -

• VCR programming information

• CD programming information

• Digital satellite receiver control data

• User information on various consumer products

EEPROM in monitor performs two functions:

• When a monitor is switch on it will copies all data or information from the EEPROM to the microprocessor. For example, the EEPROM will let the microprocessor know the frequencies at which the monitor is going to operate.

• The EEPROM is used to store the current settings of the monitor. The settings of the monitor will not be erased even when the monitor is turned off. Anytime a change is made in the monitor settings, the microprocessor updates the setting in the EEPROM. When the monitor is turn on again, the stored settings are used to set up the monitor for operation.

What are the symptoms if the MONITOR or TV’s EEPROM data is corrupted or damaged?

• No high voltage (no display).

• Horizontal or vertical frequencies run.

• Cannot save (store) current setting.

• Certain control functions like sound, brightness and contrast control does not functioning.

• On Screen Display (OSD) does not function or the OSD have a corrupted display.

• High voltage shut down (EEPROM set the horizontal frequency way too low or twice the line frequency perhaps leading to failure of the horizontal output transistor (HOT)).

What is an EEPROM programmer or copier?

EEPROM seldom fail, they just lose or have their memory (data) corrupted may be due to high voltage and static discharge from a monitor. Once reprogrammed they are as good as new. As mentioned earlier, new EEPROMs are blank and need information or data to be loaded in order for it to functions. The job of copying the data into an EEPROM is done by a programmer or a copier. Programmers comes in all shapes and sizes. You can copy these devices for repair replacement only. You cannot copy them for resale without a letter of approved from the vendor who produced them. There is quite a number of companies selling EEPROM programmer:

Typical EEPROM part no:

24C02, 24C04, 24C08 etc

24C325, 24C645AT17C65, AT17C128 etc

93C06, 93C46, 93C56, 93C66 etc

25010, 25020, 25040 etc

Jestine Yong is a electronic repairer and a writer and if you want to become a professional in testing electronic components please visit his website at http://www.TestingElectronicComponents.com