This samsung tv repair godstone came in with the complaint of wide screen and contortion (line swimming) across the vertical line of the display. Although you can modify the horizontal size, you just can’t make it into smaller and the horizontal size still big and curve inward. You could also obviously see all the up and down lines at the display have a small wave (distortion) across it. At first I think it was caused by a defective filter capacitor at secondary side of the display but all the capacitors examined to be okay.
Considering that all the caps analyzed okay, now I totally concentrate on the horizontally size and pincushion routine area. If there are any components shorted or faulty in this field, it will cause the display to go big (wide) and many times you cannot tune it back to normal size. From experienced, generally the issue was the modulation diode who have shorted or a pincushion transistor which may have leaked. But both components and all the local circuit components checked to be okay too. Applying high voltage probe to test on the anode voltage proved it to within the right range. Regarding your information, if the holddown or safety capacitor capacitance value out it could also cause the display to turn big however the high volts measured at the anode cap would be higher.
Since all the suspected components measured okay, I actually would then use volts testing to locate the fault. Just before doing the voltage test, I observed that the eeprom ic is installed just beneath the picture pipe. If any eeprom ic in any monitor located under the belly of the CRT, then chances are high the data would be corrupted by the discharge of the CRT.
If you repair some of the latest type of Samsung Monitor, you will understand why because the Samsung monitor had a piece of aluminum shielding to protect the microprocessor and eeprom IC from being discharge on it. A corrupted eeprom data could cause the mini processor to output a wrong signal to certain or all circuit. In case it send a completely wrong signal to the DPMS circuit, then the keep track of will shutdown once the power is on.
The particular ACER AJ17 eeprom IC part number was 24C08. I used to keep good eeprom data in my hardisk for future use just in situation if there is a need to reprogram the eeprom IC. I took out the eeprom IC from the board and insert it to the center outlet of the pony prog eeprom serial programmer. I then connect it to the serial port of my computer and commence to look for the good data for this model. I actually do keep a lot of ACER monitor eeprom IC data. Once I got it, I actually overwrite the old data with the good data.
Installing back the eeprom IC took only a while and the Keep track of was switched “on”. Guess what? Not only the horizontal size now returned to normal, the contortion at the vertical ranges vanished too. You better believe it that a corrupted eeprom IC could cause many weird symptoms. For some monitors, once the eeprom IC have been programmed, although the monitor work, the colour may run. Some techs are good in changing the code in the data and tune to the desire colors.