Ericsson T18 Service Manual
T18s, T18sc Standard Electrical Repairs
Approved according to 1776-2/FEA 209 544
Trouble-shooting
instruction
T18s, T18sc
Service Manual by Toko
4/00021-2/FEA 209 544/12.B
T18s, T18sc Standard Electrical Repairs
Table of contents
1 Conditions .......................................................................................... 3
2 No SERV/Not able to connect calls. ............................................... 6
3 Doesn’t start. ................................................................................... 12
4 Audio. ............................................................................................... 21
5 Display. ............................................................................................ 30
6 Charging fault ................................................................................. 34
7 SIM fault ("Insert card") ............................................................... 38
8 Keyboard ......................................................................................... 45
9 Illumination, buzzer and vibrator. ................................................ 48
10 RTC .................................................................................................. 57
11 Component list ................................................................................ 59
4/00021-2/FEA 209 544/12.B 2 (60)
1 Conditions
1.1 Component classifications.
After each component, which fault can be verified by the trouble-shooting instructions in this folder, the classification of the component is written. The components
are divided into four classes, A,B,C and D. The classes are seperated depending on
how muchof the prestanda of the phone that is affected by replacing the component.
Class A and B:Replacing the component doesn´t affect the prestanda that much,
Class C: The phone has to be calibrated at station level after replacing the com-
Class D: It demands advanced equipment and calibration at board level and
T18s, T18sc Standard Electrical Repairs
you only have to do a test call towards a real network before you perform a function test after the exchange.
ponent, since the components tolerances are so large it can affect the
prestanda of the phone.
because of that class D-components won´t be replaced.
4/00021-2/FEA 209 544/12.B 3 (60)
T18s, T18sc Standard Electrical Repairs
1.2 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, the power module at some phones.
R: Resistor.
S: Keyboard pads.
U: BALUN. A circuit that converts a signal from balanced to unbalanced or the
opposite.
V: Transistor or diode.
X: Contact surface at the circuit board.
Z: Filter.
AGND: Ground for analogue signals.
DCIO: DC voltage used for charging the battery through the system connector.
DCON: Logical signal from the processor that keeps the phone running after
you’ve released the On/Off key.
EXTAUD: Input signal at the system connector that the processor uses to deter-
mine if there’s any external audio equipment attached.
EXTAUDI: The same signal as the EXTAUD signal but at the processor side.
GND: Ground.
LED1G and LED2R:Logical signal used to activate the green or red top indicator.
LED3K: Logical signal used to activate the background illumination.
ONSRQ: Voltage from the On/Off key that starts the phone.
PORTHF: Input signal at the system connector that the processor uses to deter-
mine 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 regulators.
4/00021-2/FEA 209 544/12.B 4 (60)
T18s, T18sc Standard Electrical Repairs
RTC: Real time clock. The clock that keeps track of time and date.
SIMCLK: Clock signal from the processor, through D901, used for communica-
tions with the SIM.
SIMDAT: Data signal from the processor, through D901, used for communica-
tions with the SIM.
SIMRST: Reset signal from the processor, through D901, used for communica-
tions with the SIM.
SIMVCC: The up switched VDIG, 5 V (in D901), used for the SIM.
VBATT: Battery voltage, 4.8 V.
VBUZZ: Feed voltage to the voltage transformer for the display (becomes
VLCD and VLCDMEAS).
VCORE: Feed voltage to D600 and D900, 2.5 V.
VDIG: DC voltage for the processor and memory, 3.2 V.
VLCD: DC voltage for the display that controls the contrast.
VLCDMEAS:The same as above, but is used in N800 to measure the voltage.
VRAD: DC voltage for the radio part except the synthesizer, 3.8 V.
VRPAD: DC voltage for the radio part in D600, 3.2 V.
VRTC: DC voltage for the real time clock, 3.1 V, also existing when the phone
is powered off..
VVCO: DC voltage for the synthesizer, 3.8 V.
VVIC: Feed voltage to D901 (SIM-controller circuit), 3.2 V).
2
C: Two line serial communications standard using one clock and one data
I
line.
LO: Local oscillator.
PWM: Pulse width modulation.
4/00021-2/FEA 209 544/12.B 5 (60)
T18s, T18sc Standard Electrical Repairs
2 No SERV/Not able to connect calls.
2.1 Find out if the fault is Rx or Tx related.
Connect the phone (with signalling program) to a GSM test instrument and try to
get SERV at –68.5dBm signal strength. Check both bands (GSM 900 and 1800).
• If the phone doesn’t get SERV at any of the bands, proceed to section 2.2.
• If the phone gets SERV at the GSM 900 or the GSM 1800 band, proceed to sec-
tion 2.4.
• If the phone gets SERV but you’re not able to connect calls at any of the bands,
proceed to section 2.3.
2.2 The phone doesn’t get SERV.
Open the phone and check for liquid damages.
Make sure the back cover isn’t broken or of the wrong model since there are two to
choose from. Fig. 2.1 shows what model of back cover is to be used.
Fig. 2.1
Replace the antenna connector. Note that there are several models to choose from
and you must use the correct model. Fig. 2.2 shows what antenna connector model
is to be used.
Fig. 2.2
4/00021-2/FEA 209 544/12.B 6 (60)
T18s, T18sc Standard Electrical Repairs
Try again to get SERV at –102dBm.
• If the phone gets SERV at –102dBm there’s probably nothing wrong with the
phone. Run the phone through the final test (Go/No go-test).
Open the phone.
Give the board power and start it up by pressing the On/Off key.
Measure the VVCO voltage at pin 5 of N470 (fig. 2.3, ~3.8V).
• If the voltage is too low, replace N470 and C472 (both of class A and in fig. 2.3).
* If the voltage still is too low, send the phone to Advanced electrical
repairs.
Measure the resistances of C541-C546 (>200 kohms, fig. 2.3).
• If the resistance of any of the capacitors is too low, replace the corresponding
capacitor.
Check the solderings of Z530, C531 and L530 (fig. 2.3).
If the fault remains, send the phone to advanced electrical repairs.
4/00021-2/FEA 209 544/12.B 7 (60)
T18s, T18sc Standard Electrical Repairs
Fig. 2.3
4/00021-2/FEA 209 544/12.B 8 (60)
T18s, T18sc Standard Electrical Repairs
2.3 Connect a call at powerlevel 5 towards the
instrument with an input signal of –
68.5dBm.
If you’re not able to connect a call, open the phone and check for liquid damages.
Make sure the back cover isn’t broken and that it is of the correct model as there are
two to choose from (fig. 2.1).
Replace the antenna connector (if it hasn’t been replaced before) and try again. Note
that there are several models to choose from and it’s important to mount the correct
one (fig.2.2).
If the phone still doesn’t work then the fault is most likely Tx-related or there’s a
feed voltage fault.
4/00021-2/FEA 209 544/12.B 9 (60)
T18s, T18sc Standard Electrical Repairs
Fig. 2.4
Give the board power and start it up (in the fixture).
Measure the VRAD voltage at C482 (~3.8V, fig. 2.3).
• If the voltage is incorrect, replace N480 (class A, fig. 2.3).
Check the solderings of G300 and Z440 (fig. 2.4).
Make sure L301, C392 and V301 (fig. 2.4) aren’t burnt.
If the fault remains, send the phone to Advanced electrical repairs.
4/00021-2/FEA 209 544/12.B 10 (60)
T18s, T18sc Standard Electrical Repairs
2.4 No SERV at the GSM 900 or the GSM 1800
band.
2.4.1 No SERV at the GSM 900 band.
Measure the voltage drop of the V213 diode (~0.6V, fig. 2.3, class A).
Measure the resistance of R247 (~33 kohms, class A, fig. 2.3).
Measure the voltage at pin 3 of G201 (fig. 2.3) when you’re starting the phone.
There should be a voltage peak of ~3.5V.
• If there is no voltage peak, replace V211 (class B), V212 (class B) and C271
(class A, all in fig. 2.3).
2.4.2 No SERV at the GSM 1800 band.
Measure the voltage at pin 3 of G200 when you’re starting the phone. There should
be a voltage peak of ~3.5V.
• If there is no voltage peak, replace V211 (class B) and C270 (class A, both in fig.
2.3).
If the fault remains, send the phone to Advanced electrical repairs.
4/00021-2/FEA 209 544/12.B 11 (60)
3 Doesn’t start.
3.1 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, proceed to section 3.2.
• If the phone starts, check the charging function as described in the “Charging”
chapter (6.1.1).
3.2 Visual check.
Make an outer visual check.
• Make sure the battery connector isn’t broken and that the connector pins aren’t
dirty or oxidised.
• Make sure the system connector isn’t dirty or liquid damaged.
T18s, T18sc Standard Electrical Repairs
Open the phone and make a visual check of the circuit board.
• Check for any liquid damages and dirty or oxidised system and battery connector
pads, especially at the battery connector pads.
Fig. 3.1 shows typical dirt at the battery connector pads.
Fig. 3.1
4/00021-2/FEA 209 544/12.B 12 (60)
T18s, T18sc Standard Electrical Repairs
Make sure the dome foil isn’t damaged, especially at the On/Off key.
Make sure there are no faulty solderings at D600 (fig. 3.2, class B).
Fig. 3.2
• If the fault is fixed, send the phone through the normal flow.
If the fault remains, continue at 3.3.
3.3 Current consumption with the On/Off key
pressed.
Insert a dummy battery into the phone.
• If the phone consumes current immediately, proceed to section 3.4.1.
Start the phone by pressing the On/Off key and check the current consumption.
If the phone doesn’t consume any current when the On/Off key is being pressed it’s
most likely the dome foil that’s faulty.
• Open the phone and remove the dome foil.
• Make sure there is no liquid damages at the circuit board, especially around the
On/Off key. Any dirt at the keypads is cleaned away using a brush and alcohol.
• Mount a new dome foil (note that the circuit board must be dry when mounting a
new dome foil).
• Give the board power and start it up (in the fixture or in the back cover with the
system connector mounted to make the board lie steady).
• If the phone doesn’t consume any current when the On/Off key is being pressed,
proceed to section 3.4.2.
4/00021-2/FEA 209 544/12.B 13 (60)
T18s, T18sc Standard Electrical Repairs
If the phone consumes more than 200mA, remove the display and check again.
• The fault was due to the display if the current consumption went down.
• If the current consumption still is too high, proceed to section 3.4.3.
If the phone consumes between 1 and 200 mA, starts (asks for SIM, searches for a
net...) and works as long as the On/Off key is pressed, but shuts off at once when the
key is released, proceed to section 3.4.4.
If the phone doesn’t start, try programming it in the flash programmer.
• If the phone doesn’t start in the flash programmer, proceed to section 3.4.5.
• If you’re able to program the phone but it doesn’t start afterwards or if the phone
is troublesome in the flash programmer, proceed to section 3.4.6.
• If the phone starts after programming it in the flash programmer there’s probably
nothing wrong with the phone but to eliminate intermittent faults, check the circuit board for liquid damages and make sure there are no faulty solderings at
D600 (fig. 3.2).
3.4 Measuring a powered board.
3.4.1 Consumes current immediately (without the On/
Off key being pressed or DCIO kept high).
Open the phone and check for liquid damages.
Make sure the pads for the battery connector and system connector aren’t dirty, oxi-
dised or liquid damaged.
Remove the dome foil and clean the keypads using a brush and alcohol.
Place the circuit board in the fixture without starting it up.
Check the voltages VDIG, VCORE, VRAD, VVCO and VRPAD (fig. 3.3).
4/00021-2/FEA 209 544/12.B 14 (60)
T18s, T18sc Standard Electrical Repairs
Fig. 3.3
4/00021-2/FEA 209 544/12.B 15 (60)
T18s, T18sc Standard Electrical Repairs
Fig. 3.4
• If there’s voltage at any of the regulators, replace the corresponding regulator
(VDIG – N702, VRAD – N480, VVCO – N470, VCORE – N700, all four of
class A).
• If there’s voltage at all of the regulators, measure the voltage at pin 1 of V702
(~0V, fig. 3.4).
* If the voltage is correct, send the phone to Advanced electrical repairs.
* If the voltage is incorrect there’s probably a short circuit at the On/Off key-
pads. It’s almost always crumbs from the dome foil that causes it. Clean it
away using alcohol and a brush.
If the fault remains, send the phone to Advanced electrical repairs.
4/00021-2/FEA 209 544/12.B 16 (60)
T18s, T18sc Standard Electrical Repairs
3.4.2 Consumes no current when the On/Off key is
being pressed.
Open the phone and check for liquid damages.
Make sure the pads for the battery connector and system connector aren’t dirty, oxi-
dised or liquid damaged.
Give the board power and start it up.
Check the current consumption.
• If the phone still doesn’t consume any current, measure the resistance from the
marked side of the “No” key (On/Off, fig. 3.5) to pin 1 of V702 (fig. 3.4, ~2.2
kohms).
* If the resistance is correct, measure the resistance from pin 3 of V702 to pin
3 of N702 (fig. 3.4, ~0 ohms).
* If the resistance is correct, replace V702 (fig. 3.4, class A).
* If the resistance is incorrect there’s a foil damage and the phone is to be
discarded.
* If the resistance is incorrect there’s a foil damage and the phone is to be discarded.
Fig. 3.5
If the fault remains, send the phone to Advanced electrical repairs.
4/00021-2/FEA 209 544/12.B 17 (60)
T18s, T18sc Standard Electrical Repairs
3.4.3 Consumes more than 200mA.
Open the phone and check for liquid damages.
Make sure the pads for the battery connector and system connector aren’t dirty, oxi-
dised or liquid damaged.
Put the board in the fixture, start it up and keep it running by keeping DCIO high.
Check the VDIG (~3.2V) and VCORE (~2.5V, both in fig. 3.3) voltages.
• If any of the voltages are too low, measure the resistance from it to ground
(VDIG>48 kohms, VCORE>40 kohms).
* If the resistance is correct, replace the corresponding regulator (VDIG –
N702, VCORE – N700, both of class A).
* If the resistance is incorrect, send the phone to Advanced electrical
repairs.
• If the VDIG and VCORE voltages are correct, check the VRAD (~3.8V), VVCO
(~3.8V), VRPAD (~3.2V, all in fig. 3.3) voltages.
* If any of the voltages are too low, measure the resistance from it to ground
(VRAD and VVCO>100 kohms, VRPAD>40 kohms).
*If the resistance is correct, replace the corresponding regulator (VRAD –
N480, VRPAD – N702 and VVCO – N470), all of class A).
* If the resistance is too low there’s a short circuit in one of the circuits fed
by that voltage. Send the phone to Advanced electrical repairs.
* If the voltages are correct, measure the resistance from VBATT to ground
(>500 kohms, fig. 3.1).
* If the resistance is incorrect, send the phone to Advanced electrical
repairs.
4/00021-2/FEA 209 544/12.B 18 (60)
Loading...