EEprom Testing-Application, Operation and Failure 

Before explaining the EEprom testing subject below, you  have to know the introduction about eeprom first. Nowadays it is very common to see eeprom ic in electronic equipment. What is eeprom? EEprom means Electrical Erasable Programmable Read Only Memory and also referred to as E²PROM chip or i2c.

As the name suggest, an EEPROM can be both erased and programmed with electrical pulses from a programmer kit, burner or the equipment itself. Since it can be both electrically written into and electrically erased, the EEPROM ic can be quickly programmed and erased in circuit for reprogramming without taking them out from the main board.

EEPROM ic is also called a non-volatile memory because when the power is switched off, the stored data (information) in the EEPROM ic will not be erased or corrupt and the data is still intact. New EEPROM ic have no data (blank) inside and normally have to program it first with a programmer tools before it can be use on electronic circuit.

If you just installed a new or blank eeprom ic into a main board, even though with the same part number, I can say that the equipment will surely not going to work because the cpu or microprocessor do not know how to function.  Information or data stored in this type of memory can be retained for many years even without a continuous dc power supply to the ic. 

What is EEPROM application or operation?
EEPROMs mainly store user programmable information such as: -

• VCR programming information or data
• CD programming information or data
• Digital satellite receiver control data or information
• User information on various consumer products such as in Television.

The EEPROM ic in Computer Monitor performs two tasks: -

• When a monitor is turn on it will copies all the data or information from the EEPROM to the microprocessor or cpu. For instance, the EEPROM will let the cpu know the frequencies at which the monitor is going to run.

• The EEPROM ic is used to store the current settings of the Monitor. The current settings of the monitor will not be erased even when the monitor is switched off. Anytime when a change is made in the monitor settings, the cpu update the setting in the EEPROM (store data in eeprom). When the monitor is switch on again, the stored settings in eeprom ic are used to set up the monitor for operation. 

Assuming the data file in MONITOR or TV’s EEPROM are corrupted, damaged and failure detected, what would be the display symptoms like?

• There would be no high voltage (no display) because the cpu don’t activate the 12 volt line supply to the horizontal and vertical oscillator ic.
• The ic will not save (store) the current setting of the equipment
• Some control functions like sound, brightness, horizontal size and contrast control will not work.

• The On Screen Display (OSD) would not work or the OSD will have a corrupted or erratic display.
• Equipment high voltage will shut down (EEPROM set wrongly the horizontal frequency and will lead to a failure of the horizontal output transistor (HOT)).

What is an EEPROM programmer or copier?

EEPROM ic seldom failed or damaged, they just lose or have their memories (information) corrupted may be due to high voltage and static discharge from a monitor. There are certain types of monitor designed where the eeprom ic is located under the belly of the picture tube.

Prolong switch on and off will sometime caused the eeprom data to corrupt. That’s why you will see an aluminium shielding was installed on top of eeprom and microprocessor. If the data files already corrupted, once reprogrammed the ic, they will work as good as new. You must save first the original data into hard disk and retrieve it when testing or reprogram the ic.

For some Monitor brands where the eeprom ic data always corrupt, I have to save the good working Monitor data first for future use. As mentioned above, new EEPROMs ic are blank and no data inside and need to be loaded in order for it to work. The job of copying the data into an EEPROM is done by a programmer kit, burner or a copier.

EEprom Programmers comes in all designed, shapes and sizes. You can copy these devices data for troubleshoot replacement only. You are not allowed to copy them for resale without a letter of approved from the supplier who manufactured them. You can get the same eeprom programmer that I’m using from this website.

http://www.lancos.com/prog.html

The pony prog serial interface programming software is included and update version can be download from their website.

Typical EEPROM part numbers are: -

2402, 2404, 2408
24C02, 24C04, 24C08, 24C16
24C325, 24C645AT17C65, AT17C128
93C06, 93C46, 93C56, 93C66
25010, 25020, 25040

If you want to know more information about the eeprom ic datasheet and cross reference for testing purposes, you can always log on to internet and search for it.