Ericsson GF768 Troubleshooting Manual Download

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4/00021-2/FEA 209 544/6 C

Troubleshooting guide

Troubleshooting guide.

GF 788/768/788e Standard.

Contents

page

Component Classes

Abbreviations

Pin placements

1. RTC

2. Keyboard

3. Display

4. Charging

5. Illumination and buzzer

6. Doesn’t start

7. SIM fault

8. No serv

9. Audio

10. Spare part list

Summary of Contents for GF768

Page 1: ...oting guide GF 788 768 788e Standard Contents page Component Classes 2 Abbreviations 3 Pin placements 4 1 RTC 6 2 Keyboard 8 3 Display 13 4 Charging 18 5 Illumination and buzzer 23 6 Doesn t start 28...

Page 2: ...n replacing it Class A and B A test call towards the real net not only towards a GSM test instrument and run it through the normal tests is enough to verify the functionality since the performance of...

Page 3: ...m connector that the processor uses to determine if there s any handsfree equipment attached PHF1 The same signal as PORTHF but at the processor side REGON Logical signal that activates the voltage re...

Page 4: ...n placements Single diode PIN diode Electrolytic capacitor Double diode or single trans stor Five pin circuit usually volt age regulator Double transistor Eight pin circuit 688 VCO circuit 788 VCO cir...

Page 5: ...4 00021 2 FEA 209 544 6 C Troubleshooting guide 5 N800 D900 D600 D620 D610...

Page 6: ...or if it is halted go to 1 3 The component side of the circuit board is shown in fig 1 1 Fig 1 1 1 2 The phone shows 00 00 after removing and reinserting the battery Open the phone and make sure that...

Page 7: ...the correct time If the clock is speeding or if it is halted go to 1 3 1 3 The clock is speeding or is halted Open the phone and make sure the RTC crystal B600 is correctly soldered If it is replace...

Page 8: ...CLR and When pressing Yes the phone should try to place a call when pressing No it should disconnect it Pressing CLR should make it clear the display and and should make it scroll through the menus 3...

Page 9: ...doesn t help check the solderings at D600 pads 1 123 124 and 128 If the solderings are correct replace D600 class B fig 2 3 2 3 One or more keys non functional Open the phone and check for water damag...

Page 10: ...4 00021 2 FEA 209 544 6 C 10 Fig 2 4 Measure VDIG fig 2 5 3 2V If the voltage is incorrect go to chapter 6 If it s correct check if there s any voltage 3 2V at marked sides of R630 R631 R632 R633 and...

Page 11: ...kohms and class A If the resistances are correct check the solderings at D600 pads 120 122 128 and 1 If the solderings are correct replace D600 class B fig 2 1 If the voltages are correct at both sid...

Page 12: ...he resistance from the marked side of a working pad to a non working 0 ohms The foil damage is usually caused by water damage If for instance there s voltage at pads 4 and 5 but not at 6 and volume up...

Page 13: ...nt consumption You can also disassemble the phone give the board power start it up with the display mounted and check the current consumption that way If the phone consumes more than 200mA make sure t...

Page 14: ...If any of the resistances are too low replace the corresponding capacitor If the voltages and VRPAD are correct replace the diode If VRPAD is incorrect go to chapter 6 If the voltages at the diode exc...

Page 15: ...he voltages at the display pads H622 fig 3 4 Table 3 1 If there isn t VLCD voltage at pad 6 measure the resistances from the pad to V608 pin 1 0 ohms and from pad 5 to GND 0 ohms If any of the resista...

Page 16: ...s A and V611 class A diodes Compare the result to the values in fig 3 5 Fig 3 5 All the values are 0 2V If any of the voltages are incorrect measure the resistance of C633 class A 100 kohms fig 3 5 an...

Page 17: ...00 class B Fig 3 6 3 4 The display is completely black Open the phone and check for water damages Give the board power and start it up with the display mounted by pressing the On Off key If the phone...

Page 18: ...e phone The voltage of the battery must be so high that you can start the phone with it Otherwise the charging doesn t start immediately Cut the cable from a charger and make a charging test cable Con...

Page 19: ...4 00021 2 FEA 209 544 6 C Troubleshooting guide 19 Fig 4 1 Give the board power and start it up using the On Off key Check the VDIG VANA 3 2V fig 4 2 and VRAD 3 8V fig 4 3 feed voltages...

Page 20: ...09 544 6 C 20 Fig 4 2 Fig 4 3 If any of the voltages are incorrect go to chapter 6 If the voltages are correct send the phone to the next level When you ve repaired the fault you need to verify the ch...

Page 21: ...e resistance is too high measure the resistance of R458 class B 0 1 ohms fig 4 3 and R455 class A 390 ohms fig 4 3 If the resistances are correct measure the resistance from the marked side of R455 to...

Page 22: ...the resistance is too high measure the resistances of R458 class B 0 1 ohms fig 4 2 and R455 class A 390 ohms fig 4 2 If they are correct measure the resistance from DCIO to the marked side of R455 0...

Page 23: ...link red the battery indicator in the display should show an empty blinking battery and the phone should warn with a beep If the top indicator doesn t blink red the battery indicator doesn t show an e...

Page 24: ...5 fig 5 3 If VRPAD is incorrect or missing go to chapter 6 Fig 5 3 If the voltage at N452 pin 5 is correct measure the resistance from it to V706 pin 2 0 ohms If it s too high there s a foil damage a...

Page 25: ...rt it up If a few but not all of the LEDs aren t lit replace them If none of the LEDs are lit measure the resistance of one of them If the resistance is 0 ohms there s a short circuit in at least one...

Page 26: ...o the next level 5 5 Green top indicator doesn t work Open the phone and check for water damage Make sure the double LED H650 class A fig 5 2 isn t incorrectly soldered If the solderings are correct g...

Page 27: ...ng and the buzzer sounds faintly Open the phone and check for water damage Give the board power and start it up Measure the VRPAD voltage 3 8V at V706 pin 2 class A fig 5 2 If VRPAD is correct replace...

Page 28: ...charging function works and the phone starts lights the background illumination asks for SIM or PIN seeks net when pressing the On Off key it s probably not faulty or the fault is intermittent Open t...

Page 29: ...en the On Off key is pressed go to 6 4 2 If the phone consumes more than 200mA remove the display and try again If the current consumption went down the display was faulty If the current consumption s...

Page 30: ...30 Fig 6 3 Fig 6 4 shows measuring points for VANA VRPAD and VVCO Since the measuring point for VVCO is beneath the big radio shielding E202 you have to measure through one of the holes using a thin p...

Page 31: ...e 2 ROA 117 3748 2 all revisions boards the measuring point is placed outside the DSP shielding and is easily accessed At the 2 ROA 119 3283 7 all R4 revisions and 2 ROA 117 3632 1 all revisions board...

Page 32: ...here s no voltage at V702 pin 2 it means that the REGON signal comes from one of the regulators or from V704 V708 or V709 fig 6 6 V708 and V709 aren t used in the 2 ROA 117 3748 2 boards all revi sion...

Page 33: ...25 kohms If the resistance is correct replace the corresponding regulator VDIG N702 VANA N700 VDSP N701 all class A The VDSP regulator can only be replaced at this level if the circuit board is a 2 RO...

Page 34: ...evel If all of the feed voltages are correct measure the amplitude of the 13MHz master clock at C680 class A 0 6V t t fig 6 4 D900 fig 6 2 usually gets hot when the clock signal is missing If the sign...

Page 35: ...d in the fixture Start it up and keep it running by keeping DCIO high Measure VANA and VDIG 3 2V fig 6 4 and 6 3 If any of the voltages are too low measure the resistance from it to ground VDIG 500 oh...

Page 36: ...e corresponding regulator In that case send the phone to the next level If any of the voltages are to high replace the corresponding regulator Check VRAD fig 6 9 3 8V VVCO fig 6 4 3 8V measure through...

Page 37: ...t part of the level 3 test If PIN or Enter PIN appears in the display it means that the SIM card is locked with a personal code Only if Insert card appears in the display there s a SIM fault 7 2 Measu...

Page 38: ...ard Fig 7 3 Fig 7 4 If the input voltage is too low or missing check the VDIG feed voltage 3 2V at C600 fig 7 4 If VDIG is too low measure the resistance from it to ground 500 ohms If it s correct rep...

Page 39: ...phone is to be discarded 7 4 VSIMPAD voltage is correct Open the phone and check for water damage Clean the SIM pads X600 fig 7 3 using alcohol and a brush Assemble the phone with a new SIM holder an...

Page 40: ...f the correct model since there is two kinds Fig 8 1 shows what kind of back cover is to be used with which board Fig 8 1 Replace the antenna connector and try again Note that there are different mode...

Page 41: ...ke sure the back cover is of the correct model since there is two kinds Fig 8 1 shows what kind of back cover is to be used with which board Replace the antenna connector if it hasn t been replaced ye...

Page 42: ...el value is too high and therefore you have to send it to the next level If the Rx level is below 38 steps at 68 5dBm signal strength or below 5 steps at 102dBm signal strength the fault is Rx related...

Page 43: ...sound in the reference phone go to 9 3 If both the microphone in the phone and the microphone of the handsfree don t work send the phone to the next level If both the microphone and the earphone don...

Page 44: ...moving the system connector Fig 9 3 Make sure the sound channel gasket is properly mounted and free from dust Replace the system connector and microphone with a pair you know works Test the phone agai...

Page 45: ...5 Fig 9 4 9 4 Both the earphone and the microphone of the phone out of order Open the phone and check for water damages Make especially sure there s no dirt or oxide between the components below the d...

Page 46: ...the measuring point for VDSP The figure shows three possible placements of the VDSP regulator At the 2 ROA 119 3283 7 R2A and 2 ROA 117 3748 all revisions boards the regulator is placed outside the D...

Page 47: ...o low replace the corresponding resistor fig 9 4 and 9 5 both of class A If the voltage is too low at both sides of R601 or R605 check the VSIMPAD voltage at marked sides of R635 and R636 5V fig 9 4 R...

Page 48: ...rrect connect a handsfree to the system connector Measure the voltage at both sides of R601 0V fig 9 4 and at D600 pin 70 0V If the voltage isn t correct check the soldering at D600 pin 70 fig 9 2 If...

Page 49: ...e system connector pads X602 fig 9 8 1 2 and 4 Measure the resistance of C850 and C851 both 100 kohms of class A and in fig 9 4 Make sure all the components in fig 9 10 R803 R804 and C813 are mounted...

Page 50: ...nted on 2 ROA 119 3283 7 R4C C692 RJC 464 3035 68 C710 RJC 464 3046 1 C720 RJE 338 1256 6 C810 RJC 464 3035 33 C812 RJC 464 3035 68 C813 RJE 599 2107 15 C816 RJC 464 3024 12 C818 RJC 464 3035 68 C819...

Page 51: ...8 2 3 N701 RYT 113 6095 1 N702 RYT 113 6057 4 RYT 113 6279 1 Mounted on 2 ROA 117 3748 2 3 N703 RYT 113 6040 5C N705 RYT 113 048 C N706 RYT 113 6071 5 R455 REP 645 620 1 R458 REP 645 623 39 R600 REP 6...

Page 52: ...REP 622 654 39 REP 622 655 1 Mounted on 2 ROA 117 3748 2 3 R803 REP 622 456 1 R804 REP 622 456 1 R805 REP 622 655 15 REP 622 654 56 Mounted on 2 ROA 117 3748 2 3 R816 REP 622 453 47 R817 REP 622 454 1...

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