lcd all segments disappear after a while of turning it on

[abdolah]

LCD IN MM-26 HIFI sound amplifier device 
lcd all segments disappear after a while of turning it on
lcd part no :  AH7-10035A
lcd driver : LC72362n

PIN 55=lcd DRIVER SUPPLY power bias = 4.8v . test on board 4.8v
pin 56=VLC 0=4.9v . on board test 4.4v
pin 57=VLC 1=3.1v . on board test 2.3v
pin 58=VLC 2=1.6v . on board test 1.2v

the problem is the disappearance of all the segments after a while of turning it on after replacing some caps the problem take longer to appear
backlight always on 
service manual
https://data2.manualslib.com/pdf5/118/11707/1170619-samsung/mm26.pdf?5b9666aa11c8a6af062235031239619b&take=binary

[Swake]

Found attached datasheet for the driver LC72362N, but it does not match the table on page 9-11 of the service manual that you linked and nothing in the datasheet about driving LCD's. So, something is wrong here.
Some other chips in the same family have LCD drivers. such as the LC7230 and LC72323 but it doesn't match the service manual either. Do you have any better information?

Can you measure ripple on the power supply lines?

Is anything running hot? If you do not have a thermal camera you can check for a heating using a quickly evaporating alcohol based solution such as IPA or lighter fluid. Apply the fluid over some area, then switch on the device, if the fluid evaporated quickly on one of the components then that is a suspect.

[hummerjanne]

Does your device have eeprom?

[abdolah]

no idont think so . it has a memory to remember the last settings for the volume and the equalizer 
 but not sure what does that do with all the segments disappearing
   

[abdolah]

the driver number is in the service manual

no i don't have an oscilloscope unfortunately

no nothing is getting hot .. no short . etc
the device is working but after a while of turning the device on and let it working for maybe an 1 hour  this problem appears
 

[wraper]

All segments disappearing could easily mean firmware crashing. If not refreshed, LCD will keep showing its last state but will fade away gradually. Or everything could disappear instantly, depends on how it's driven. LCD itself would not be my first suspect. Does everything else actually function besides LCD showing nothing? Sound may be still coming but can you say change the volume or do something else?

[abdolah]

yes everything else works fine even when the segments start disappearing the device is fully function . the buttons are responding no problems . the screen response is the problem

when the problem starts when pressing any buttons some segments of the screen will appear and slowly disappear  .. including the volume buttons . the text will appear and slowly disappear
same when holding the buttons 

[Swake]

When you switch it off for about 15 to 30 minutes will it work normally again after that?

You can try to re-solder all the connections of the LCD and the surrounding components.
If the LCD is connected with a zebra strip then dismantle everything very gently, clean the strip with clear water and a very clean cloth.

[tom66]

I think zebra strip is a possible problem too. Have you applied pressure to the front panel when the problem occurs, do the segments appear to fade in and out?

[abdolah]

yes after the problem appear turning it off for Like  haLf an hour and turning it back on will fix it but the problem will be back after a while

NO DRY solder JOINTS , I have re solder  all the joints with fresh Solder
the screen is not connected via stripe it's connected using a CONDUCTIVE Glue     

[abdolah]

only when buttons pressed
I will check again on the screen to see if it's connected via a stripe or not
if it's I will clean it with some Isopropyl Alcohol and I will tell you the result

[Swake]

It points in the direction of a thermal issue or some charge building up over time.

When the issue appears, try cooling down component by component to find out the location of the issue. Cool it with compressed air. Eventually you could use 99% IPA if you have a sprayer. Avoid using 70% IPA or similar on powered up equipment, this can cause shorts because of the water content.