Old Ericsson GH-337 no singal & display problem...

[Ken-mkII]

Hi there:

Recently, my friend gave me and old Ericsson GH-337 GSM phone. Which still can power up, but can't make/receive call, others is okej beside the LCD display is a little bit burr...

After power up, the phone keeps displaying "Seraching...." on the LCD...., and if I switch to use manual seraching and select net function in the menu, it can find those network and display the code (460-00, 460-01 etc), but just can't logged in. So I bet this should be the problem of the transmit module problem at first.

But.... if I put the phone beside the amplifer and then turn on the phone, I can hear "DU... DU...du...du..." (But the sound still different with normal working phone) from the speaker of the amplifer, it means the phone tried to transmit the singal out to hand-shake w/ the network but then the singal drop....

So, I connect an amp meter to check the transmit current after the phone power on, it display around 350ma then drop to around around 150ma... 0.5 sec later, 350ma-150ma-... continully.

Then I keep it running.... Suddenly, the LCD freeze, but after press those keys, I can still hear the click sound from the buzzer, it means the phone is not dead yet. Then power off and on again, the LCD become BLACK blocks!! Can't see any charactors... But still can hear the click sound when I press those key on keypad....

So, I use a power supply to supply the voltage to the phone and check the voltage when the phone's LCD will freeze and turn black, Around 6.3v, the phone's LCD will freeze, if I re-power up the phone on this voltage, the LCD will become all black after power up. But if increase the voltage to upper (6.5v), the LCD will display normally after power on the phone.....

So..... What is the problem of the phone?? Is it really the transmit module burn??? Beside, as the LCD problem, is it the data storage in EEPROM is corrupted? As this is an old phone, I don't have any information to repair it....

Does anyone would like to help me on it and give me some ideas??

Thanks a lots, and sorry for my bad english.

Best regards,
Ken Yaksa

[genocite]

eeprom maybe corrupted if the display encounter any problem, signal could be related to it ...