Ericsson GF 768 Troubleshooting Manual
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Ericsson GF 768 Troubleshooting Manual

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4/00021-2/FEA 209 544/6 C
Contents
Troubleshooting guide.
GF 788/768/788e Standard.
Troubleshooting guide
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Summary of Contents for Ericsson GF 768

  • Page 1: Table Of Contents

    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.

  • Page 2: Component Classes

    Troubleshooting guide 4/00021-2/FEA 209 544/6 C Component classes. All the components in the phone are divided into classes and after every component in the troubleshooting guide you have a class written. The components are divided into four classes: A, B, C and D.The class of the component depends on how much of the phone’s performance is affected when replacing it.

  • Page 3: Abbreviations

    4/00021-2/FEA 209 544/6 C Troubleshooting guide Abbreviations. A: The power module at some phones. B: Crystal. C: Capacitor. D: Digital circuit. F: Over voltage protection. G: VCO. H: Buzzer, LED, pads for display. J: Connector. L: Coil. N: Analogue circuit. R: Resistor.

  • Page 4: Pin Placements

    Troubleshooting guide 4/00021-2/FEA 209 544/6 C Pin placements Single diode (PIN diode). Electrolytic capacitor. Double diode or single trans- Five pin circuit (usually volt- Double transistor. stor. age regulator). Eight pin circuit. 688 VCO circuit 788 VCO circuit Sixteen pin circuit Twenty pin circuit Crystal...
  • Page 5 4/00021-2/FEA 209 544/6 C Troubleshooting guide N800 D900 D600 D620 D610...

  • Page 6: Rtc

    Troubleshooting guide 4/00021-2/FEA 209 544/6 C 1. RTC Find the fault. Start the phone with a SIM-card and a fully charged battery inserted. Set the correct time. Remove the battery and reinsert it after a minute. • If the clock says 00:00, go to 1.2. Compare to the correct time.
  • Page 7 4/00021-2/FEA 209 544/6 C Troubleshooting guide a few hours of charging to get fully charged). Compare to the correct time. If the clock is speeding or if it is halted, go to 1.3. The clock is speeding or is halted. Open the phone and make sure the RTC crystal, B600, is correctly soldered.

  • Page 8: Keyboard

    Change the menu size to extended. Go to “Settings/Key sound” in the menus and change to “click”. Applies for GF 768/768c: Go to “Key sound” in the menus and change to “click”. Press the keys 1, 2, 3…*, 0, #. A clicking sound should be heard and the corresponding sign should be shown in the display at every key pressed.
  • Page 9 4/00021-2/FEA 209 544/6 C Troubleshooting guide Fig. 2.2 • If the resistance is high all the time, replace the corresponding microswitch. • If the resistance is low all the time, replace the corresponding microswitch. If that doesn’t help, check the sol- derings at D600 pads 1, 123, 124 and 128.
  • Page 10 Troubleshooting guide 4/00021-2/FEA 209 544/6 C 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 R634 (all in fig.
  • Page 11 4/00021-2/FEA 209 544/6 C Troubleshooting guide Fig. 2.5 • If the voltage is missing at one or more of the resistors, measure the resistance from marked side of C600 to the marked side of the resistor (~0 ohms). If the resistance is too high there’s a foil damage and the phone is to be discarded.
  • Page 12 Troubleshooting guide 4/00021-2/FEA 209 544/6 C Fig. 2.6 If voltage is missing at some keys in a row (se functional scheme fig. 2.4) there’s a foil damage and the phone is to be discarded. This is verified by measuring the resistance from the marked side of a working pad to a non-working (~0 ohms).

  • Page 13: Display

    4/00021-2/FEA 209 544/6 C Troubleshooting guide 3. Display. Type of fault. Insert a fully charged battery into the phone and start it up. • If it doesn’t start, go to chapter 6. • If the display is missing one or more segments, go to 3.2. •...
  • Page 14 Troubleshooting guide 4/00021-2/FEA 209 544/6 C Fig. 3.2 All the values are 0.2V . If any of the voltages are incorrect, measure the resistance of C633 (class A, >100 kohms, fig. 3.2) and C824 (class A, >25 kohms, fig. 3.2). •...
  • Page 15 4/00021-2/FEA 209 544/6 C Troubleshooting guide Fig. 3.3 Fig. 3.4 If the voltages at V608 are correct but the display is totally empty when phone is on, measure the voltages at the display pads, H622 (fig. 3.4): Pad # Name Voltage ~3.2V C-CLOCK...
  • Page 16 Troubleshooting guide 4/00021-2/FEA 209 544/6 C carded. If I C-DATA or I C-CLOCK voltage is missing, check VDIG at C600 (~3.2V, fig. 3.2). • If VDIG is incorrect, go to chapter 6. • If VDIG is correct, measure the resistance of R619 (class A, 2.2 kohms, fig. 3.2), R620 (class A, 2.2 kohms, fig 3.2), R615 (class A, 10 kohms, fig.
  • Page 17 4/00021-2/FEA 209 544/6 C Troubleshooting guide Pad # Name Voltage ~3.2V C-CLOCK VDIG ~3.2V VLCD ~-5V ~3.2V C-DATA Table 3.2 • If there isn’t VLCD voltage at pad 4, measure the resistances from the pad to V608 pin 2 (~0 ohms) and from pad 2 to GND (~0 ohms).

  • Page 18: Charging

    Troubleshooting guide 4/00021-2/FEA 209 544/6 C 4. Charging. Type of charging fault. Make a visual check of the battery and system connector. Replace if needed. Insert a fully charged battery and start the phone. • If it doesn’t start, go to chapter 6. •...
  • Page 19 4/00021-2/FEA 209 544/6 C Troubleshooting guide 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 Troubleshooting guide 4/00021-2/FEA 209 544/6 C 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 charging function as described in 4.1.1.
  • Page 21 4/00021-2/FEA 209 544/6 C Troubleshooting guide The phone doesn’t start when charger is inserted. Open the phone and check for water damage, especially at the system connector. The phone is to be discarded if the gold plating is damaged like in fig. 4.4. Fig.
  • Page 22 Troubleshooting guide 4/00021-2/FEA 209 544/6 C When you’ve repaired the fault you need to verify the charging function as described in 4.1.1. Starts, doesn’t charge but indicates charging. Open the phone and check for water damage, especially at the system connector. If the gold plating is damaged like in fig.

  • Page 23: Illumination And Buzzer

    4/00021-2/FEA 209 544/6 C Troubleshooting guide 5. Illumination and buzzer Type of fault. Insert a dummy battery and a SIM card into the phone, press the On/Off key and wait for the phone to get serv (with the test instrument or the GSM-net). •...
  • Page 24 Troubleshooting guide 4/00021-2/FEA 209 544/6 C Fig. 5.2 • If the voltage at H600 pad 4 is missing, measure the voltage at VRPAD (3.8V) at V706 pin 2 (class A, fig. 5.2. • If the voltage is missing, check if VRPAD is at N452 pin 5 (fig. 5.3). •...
  • Page 25 4/00021-2/FEA 209 544/6 C Troubleshooting guide • If it’s correct, replace V706 (class A). Measure the resistance from H600 pad 1 to V606 pin 3 (~0 ohms, fig. 5.2). • If it’s too high there’s a foil damage and the phone is to be discarded. •...
  • Page 26 Troubleshooting guide 4/00021-2/FEA 209 544/6 C Table 5.1 If none of the LEDs, H651-H654 and H655-H660, are lit, measure the voltage at the marked side of R607 (~3.1V, fig. 5.4). Before measuring you have to press a key for the processor to set the LED3K signal high for about 10s.
  • Page 27 4/00021-2/FEA 209 544/6 C Troubleshooting guide • If it’s too high there probably is a foil damage between VBATT and V706 pad 3 and the phone is to be discarded. • If it’s correct, replace V706 (class A). Check the soldering at D600 pin 93. If the fault remains, send the phone to the next level.

  • Page 28: Doesn't Start

    Troubleshooting guide 4/00021-2/FEA 209 544/6 C 6. Doesn’t start. Find out if the phone starts when pressing the On/off key. Insert a fully charged battery into the phone and press the On/Off key. • If the phone doesn’t start, go to 6.2. •...
  • Page 29 4/00021-2/FEA 209 544/6 C Troubleshooting guide As soon as the fault is fixed, send the phone through the normal flow. Visual check. Make an outer visual check. Make sure the battery connector is intact and that there aren’t any dirt or oxidation at the connector pins. Make sure the system connector isn’t dirty or water damaged.
  • Page 30 Troubleshooting guide 4/00021-2/FEA 209 544/6 C 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 probe (preferably iso- lated) as in fig.
  • Page 31 4/00021-2/FEA 209 544/6 C Troubleshooting guide Fig. 6.5 Fig. 6.6 shows the measuring point for VDSP. The picture shows 3 different locations where the VDSP regulator could be placed. At the 2/ROA 119 3283/7 (R2A) and the 2/ROA 117 3748/2 (all revisions) boards the measuring point is placed outside the DSP shielding and is easily accessed.
  • Page 32 Troubleshooting guide 4/00021-2/FEA 209 544/6 C Fig. 6.8 Fig. 6.9 • If there’s voltage at one of the measuring points, replace the corresponding regulator. VDIG – N702, VANA – N700, VDSP – N701, VRAD – N453, VVCO – N451 and VRPAD – N452 (all of them class A). •...
  • Page 33 4/00021-2/FEA 209 544/6 C Troubleshooting guide 6.4.2 Doesn’t consume any current when On/Off key is pressed. Open the phone and check for water damage. Make sure there aren’t water damage, dirt or oxidation at the battery or system connector pads. Give the board power and start it up by pressing the On/Off key (in the fixture or in the back cover with a dummy battery inserted, mount system connector to make the board lie steady in the back cover).
  • Page 34 Troubleshooting guide 4/00021-2/FEA 209 544/6 C • If the resistance is too low, send the phone to the next level. 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.
  • Page 35 4/00021-2/FEA 209 544/6 C Troubleshooting guide 6.4.4 The phone runs as long as the On/Off key is pressed. Open the phone and check for water damage. Make sure there aren’t water damage, dirt or oxidation at the battery or system connector pads. Mount the board in the fixture, start it up and keep it running by keeping the On/Off key pressed.
  • Page 36 Troubleshooting guide 4/00021-2/FEA 209 544/6 C you’ve verified that the amplitude of the master clock is correct. Try programming the phone after every component replaced. If the fault remains, send the phone to the next level. 6.4.6 Is programmable but doesn’t start afterwards or is troublesome in the flash programmer. Open the phone and check for water damage.

  • Page 37: Sim Fault

    4/00021-2/FEA 209 544/6 C Troubleshooting guide 7. SIM fault (“Insert card”). Definition of SIM fault. Insert a functional SIM card and a fully charged battery into the phone. Start it up using the On/Off key. • If “Wrong card” or “Insert correct card” appears in the display it means that the phone is SIM locked and can’t be repaired at this level.
  • Page 38 Troubleshooting guide 4/00021-2/FEA 209 544/6 C age at N705 pin 2 (~3.1V, fig. 7.4). Fig. 7.3 shows the component side of the circuit board. 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). •...
  • Page 39 4/00021-2/FEA 209 544/6 C Troubleshooting guide next level. • If VDIG is correct, measure the resistance of R706 (class A, ~4.7 ohms, fig. 7.4). Note that at the 2/ROA 117 3632/1 boards the resistor is placed as in “AREA B” in fig 7.4. •...

  • Page 40: No Serv

    Troubleshooting guide 4/00021-2/FEA 209 544/6 C 8. No serv or not able to connect calls. Find out if the fault is Rx- or Tx-related. Connect the phone (with signaling program) to a GSM test instrument and try to get serv at –68.5dBm signal strength.
  • Page 41 4/00021-2/FEA 209 544/6 C Troubleshooting guide Fig. 8.3 • If the resistance is too low, replace Z200 (class B, fig. 8.3). The resistance usually becomes a few ohms when Z200 breaks. Give the board power and start it up by pressing the On/Off key (in the fixture or in the back cover with a dummy battery inserted, mount system connector to make the board lie steady in the back cover).
  • Page 42 Troubleshooting guide 4/00021-2/FEA 209 544/6 C Read the Rx-level value from the instrument while call is connected. If the RX-level value is at 43 3 steps mak e sure the output power is 31-35dBm. • If it is, the phone probably isn’t faulty. Lower the signal strength to –102dBm and make sure the Rx-level is 6- 12 steps and that the Rx-quality is 0-2 steps.

  • Page 43: Audio

    4/00021-2/FEA 209 544/6 C Troubleshooting guide 9. Audio. Type of fault. Make a call from the phone that is to be tested (later called the phone) to a phone that is working correctly (later called the reference phone). Check the function of the microphone and the earphone. Connect a handsfree unit to the system connector of the phone.
  • Page 44 Troubleshooting guide 4/00021-2/FEA 209 544/6 C Fig. 9.2 If the fault remains, send the phone to the next level. Microphone out of order. Open the phone and check for water damages. Wash the system and microphone connector pads if needed. Most of the microphone faults are mechanical.
  • Page 45 4/00021-2/FEA 209 544/6 C Troubleshooting guide Fig. 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 dome foil (fig. 9.5) and at the system connector pads.
  • Page 46 Troubleshooting guide 4/00021-2/FEA 209 544/6 C Fig. 9.5 Wash the circuit board if needed using alcohol and a brush. Assemble the phone and test it as in 9.1. If the fault remains, open the phone. Give the board power and start it up by pressing the On/Off key without the system cable connected.
  • Page 47 4/00021-2/FEA 209 544/6 C Troubleshooting guide Fig. 9.7 • If the VDSP voltage is too low, replace N701 (class A, fig. 9.6). The N701 circuit can only be replaced at 2/ ROA 119 3283/7 R2A boards. At the other boards the circuit is placed under the DSP shielding (E203). If that’s the case, send the phone to the next level.
  • Page 48 Troubleshooting guide 4/00021-2/FEA 209 544/6 C • If the resistance increased, replace D600 (class B, fig. 9.2). • If the resistance didn’t increase when removing the R601 resistor or if it didn’t help to replace D600, send the phone to the next level. •...
  • Page 49 4/00021-2/FEA 209 544/6 C Troubleshooting guide circuit board (fig. 9.4). Check the solderings of N800 (fig. 9.2). Give the board power and start it up by pressing the On/Off key without the system cable connected. Measure the voltage at the marked side of R825 (~3.1V, fig. 9.4). •...

  • Page 50: Spare Part List

    Troubleshooting guide 4/00021-2/FEA 209 544/6 C Spare part list Standard repair, 700 series 10.1Electrical Componets Partslist Positon Part number Note B600 RTM 501 661/01 C632 RJC 463 3022/56 C633 RJC 464 3035/68 C634 RJC 463 3023/18 Only on 2/ROA 117 3632/1 C680 RJC 464 3023/33 C690...
  • Page 51 4/00021-2/FEA 209 544/6 C Troubleshooting guide Positon Part number Note H656 RKZ 433 634/4 H657 RKZ 433 634/4 H658 RKZ 433 634/4 H659 RKZ 433 634/4 H660 RKZ 433 634/4 J810 SXA 120 5152 SXA 104 4014 Mounted on 2/ROA 117 3748/2 & /3 and 2/ROA 119 3632/1 R2A and above J820 RMD 955 101/01...
  • Page 52 Troubleshooting guide 4/00021-2/FEA 209 544/6 C Positon Part number Note R630 REP 622 456/1 R631 REP 622 456/1 R632 REP 622 456/1 R633 REP 622 456/1 R634 REP 622 456/1 R635 REP 622 455/22 R636 REP 622 455/22 R651 REP 622 454/1 R704 REP 622 456/1 R706...

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