Part identification and Trouble-shooting procedure:

• Do not apply power to the module until the following steps are completed:

• Visually inspect the board for part placement. (Exercise I: Identify correct parts, and values).

• Diode’s cathodes (-) can be identified with a thick black line on the device, or a brown line (glassy diode), or a white line), or a half-circle notch, SMD diodes with sot-23 package: solo pin is the cathode, left pin on the dual-pin side is anode. Check for good diodes: Using a Volt Meter the positive to negative resistance should be in the range of K Ohms, the opposite should be in the range of M Ohms. Using diode test setting, the voltage from + to – should be 0.5 to 0.7volts, the opposite should be several volts to “overload”, depending on type of volt meter.

• Capacitors: Electrolytic caps (-) is cathode, (+) is anode, ceramic and chip capacitors mostly are unmarked, and non-polarized, Tantalum cap’s usually are in yellow, the line indicating positive (+), (opposite to diode’s marking). The voltage rating (eg. 16V, or 50V) on Electrolytic capacitors are important, over voltage will result in overheat or a little explosion. Chip capacitors are in brown or yellow color. Should measure as open circuit (high resistance) with DC, and short circuit (low resistance) with AC (high frequency).

• Transistor: Sot-23 package, solo pin is Collector, Base on the left, Emitter is on the right (looking into the part with solo on the head orientation). The silkscreen (symbol) of transistors may be Q123, or T12. Check for good bipolar transistors: using a volt meter on a NPN transistor, base to emitter should measure like a diode, collector to emitter should have same reading as a diode too. For PNP transistor, the measurements are reversed.

• Resistors: Chip resistors are in black or blue color. Most are 10% tolerance, 1% resistors mostly are in 1206, and blue color. Leaded resistor values are in color band. SMD resistor values are the small numbers on the back. Resistors are non-polarized. Their physical sizes can vary from 0503 to very large ones.

• Inductors: leaded inductors usually have exposed copper wires going around an circular or an I-core. SMD inductors are in yellow, or black color. They cannot be easily identified. Should measured a short circuit with DC, and high impedance with high frequency. Adjustable inductors can be tuned using a non-metallic tool. Symbol: L123

• Relay: Micro-relay looks like an IC with black plastic package. It can not be easily identified. Symbol: K123 or Y 123

• Crystal or ceramic oscillator: May be in a metal can, circular, rectangular, or in chip form. Or in bright orange, yellow, blue rectangular package. Usually are non-polarized. Symbol: X1, Y2, Z1

• Thermistor: SMD thermistors can look like inductors, dark and unmarked. Reset-able thermistors looks like disc capacitors or MOV’s. They may be in yellow, rectangular shape with 2 leads. Usually has a bump on the disc. PTC type thermistor’s resistance is proportional to temperature. NTC type’s resistance is inversely proportional to temperature. Reset-able fuses will return to the normal state after power is removed for a few minutes. Some fuses are inserted in the wires. Symbol: V12, F1

• IC: Pin #1 can be identified by a dot, or a cut-corner. Pin arrangement is counter-clockwise.

• (Exercise II: Measure transistor’s resistance)

• Open circuit vs. Short circuit with DC

• Read schematics and layout plots: check for correct version of the drawings. Identify external connectors and pins. Identify Power supply and ground pins. Power supply and ground pins for IC’s are not shown sometimes. Ground symbols may be different from US, Japan or European’s. Input and output symbols. Pin #’s on the IC’s may not match the ones on the drawing. What are refdes (reference designators)? Pad size and orientation. 0603, 0805, 1206, 2010, 2512. Connector pins arrangement. Traces on the board: cut or short problem. Operation Amplifier and logic gates drawings may be shown partial. There are usually two or four devices on one IC. Not all the devices are used or drawn. The power supply to these IC’s are not always shown. The devices can be tested by manually feed signal into the input pins, and observe the result from output.

• Circuit board: FR4, Flex, ETM circuit board ground layer. Soldering and repair procedure. What to look for when you receive a new board? Silkscreen, pad, solder mask, fiducials, test points, part orientation.

• Ready Instruments: Oscilloscope, Power supply, micro-ohm meter, emulator, logic analyzer, impedance analyzer, spectrum analyzer and volt meter settings, type of probes. When and how to use these instruments. What and where are ATE’s? Wave forms seen on scope. Where to probe? What to look for?

• Measure all Power Supply pins (Such as Vpwr, Vcc, Vdd, Vbat, A+, Vign, IGN, Vkav, or KL_30) pins to Ground resistance, and check for short circuit between power supply and ground.

• Measure all Power Supply pins (Such as Vpwr, Vcc, Vdd, Vbat, A+, Vign, IGN, Vkav, or KL_30) pins to each other’s resistance, and check for short circuit among power supply lines.

• Measure I/O open and short. Visually inspect all polarized parts such as diodes, capacitors.

• Measure the continuity of all I/O's from the connector pins to the controller IC pins. Identify the main micro-controller IC: by crystal or ceramic oscillator, or by a glass window on the back of IC. Look for cold soldering, circuit board defects, poor contacts between pin and socket, and pin-assignment problem.

• Power up the test unit on bench, starts with minimum voltage such as 5.5V. Typical test voltage for automotive device is 12.5V DC. Maximum is 18V DC.

• Symptoms of problem: How to tell if there is something wrong? Vcc is not present. Draw too little or too much current. Parts overheated. OSC not running. Output not present. No response from input

• Partial circuit test, and Isolation of circuits. Micro-controller failure modes. DC test(presence of power supply, Regulated voltage output, stand-by and operating current draw), AC test( timing delays), RF (frequency and magnitude) , and Functional tests. Screen room effect.

• Cut traces or solder jumper wires wisely.

• (Exercise III: Identify and fix a “dark current” failure problem)

• Exercise the module in all possible operation modes such as AM, FM, Tape, IGN on, lamp and observe the current draw and oscillator frequency. Which components need oscillator? Answer: Any circuit that requires clock source, or frequency source such as Radio tuner, or Remote control device.

• Use ATE (Automatic Test Equipment) to test PCM or Radio or other modules where applicable, to characterize the unit, and compare with specifications

• Run cold, hot, vibration, and all other necessary tests to screen the units. Look for high stand-by current and intermittent malfunction.

• Run In-Vehicle test. Using OBDC tester.