Set multi meter to Diode Mode
Connect negative probe to ground (USB ground)
Connect positive probe to middle pin of charging port
If reading shows OL, it means NO short to ground.
Connect positive probe to ground (USB ground)
Connect negative probe to middle pin of charging port
If reading shows 0.9 v, it means Good
If reading shows OL, it means circuit is Open
Laptop Voltages
19 volts
5.0 volts - USB, Fan
3.3 volts - bios chip
1.3 volts - RAM
0.8-1.1 v - CPU
0.8-1.1 v - graphics
Schematics: http://laptop-schematics.com
Samsung Tab 3 &/or Tab 4
Problem: lines and funny colors on screen, image pixelated
Solution: First disconnect battery. Then check screen cable if properly seated. Remove cable & clean all contacts.
HP G6-2210SA
Problem: Dead laptop
Set multi meter to VDC setting
Diagnostics: Check for 19 volts on charging port. Check for 19 volts on power-supply capacitor next to the 4 mosfet. Check voltage on last pin of bios chip. It should read 3.1 volts.
Set multi meter to DIODE mode
Trace the positive voltage PATH from charging port connector (19-volt positive pin) to 1st mosfet chip pins. 0.0 volt reading here indicates continuity &/or connectivity.
Note: On the 1st IC mosfet all input pins are connected/soldered together.
With positive probe still on positive pin of charging port connector, touch negative probe to ground. OL reading means no short to ground. 0.0 volt reading means there's a short.
With positive probe now touching the 1st IC mosfet input pins, touch negative probe to output pins. 0.0 volt means good continuity &/or connectivity.
Next component (2nd mosfet, which is a large transistor). Touch negative probe to the metal electrode of the of the 2nd mosfet (transistor). 0.0 volt reading indicates connectivity &/or continuity.
Next touch positive probe on metal electrode of 2nd mosfet (transistor). Touch negative probe to one of the pins of 2nd mosfet. 0.0 volt means continuity &/or connectivity.
Next with negative probe still on one of the pins of 2nd mosfet, touch positive probe to ground. 0.0 volt means short to ground.
Apply voltage to board & feel for any warm or hot component. Apply petrol or alcohol to suspected component. The shorted component will quickly evaporate any petrol or alcohol applied to it.
Asus S200E
Problem: Dead laptop
Check voltages starting at charging port. 19 volts should be present. Continue to trace the 19 volts to next components (2 IC chip switches) located at the back of the mother board. On the first chip, 19 volts should pass through the output pins. If NOT, remove the faulty chip and bridge the input pins to the output pins.
Connect charger & trace for the 19 volts on the area where the first chip was removed, continuing to the input & output pins of the 2nd IC switch, to the resistor next to it.
3.1 volts should also be present in the last pin of bios chip.
Sony VAIO SVF152C29M
Problem: No backlight on screen
Light on LED screen has nothing to do with the picture/image being displayed. Start-up chip (SMC, ATA, ITE, ENE, WINBOND or any other brand) should receive a signal from the graphic card. Once that signal is received, that chip will order the screen to enable or tun on the light. There are 2 pins (3.3 volts) one is for brightness & the other is the LED On.
19 volts should also be present on the inverter.
Any graphic issue, it will result in no light. In order to have light the graphic card should be in good working condition. Ninty-nine percent of the time if the graphic card is fine, there should be light. However, it may also be possible that a fault in the graphic card may still produce the light on the screen. Symptoms on the screen would be lines, funny colors & pixelated images.
No light with picture: Possible faults would be broken ribbon cable, connector, graphic card or RAM.
No picture but with light: Possible faults would be broken ribbon cable or screen issue.
IMPORTANT: Before removing or replacing the screen connector make sure the battery is removed and the charger is disconnected. If not observed, this may damage the processor of the graphic card.
Diagnosis: No 19 volts on inverter. 19 volts should always be present, that's why it's important to remove the battery first before working on the screen.
Solution: Replace open fuse with a 5-ohm resistor on 19 volt supply to the screen.
Lenovo g50-30
Problem: Laptop won't power ON. All voltages, however, are present when mother board was checked.
Solution: Short BIOS battery pins with tweezers. Re-heat start-up chip, remove RAM memory & re-install battery.
Acer Cromebook SB5-571
Problem: Laptop won't power ON but has blue light on.
Solution: Once back cover is removed, disconnect battery connector & wait for about 3 minutes before re-connecting. Battery was charged using bench power supply at 2 amps for about 3 minutes..
Acer E1-571
Problem: Laptop won't power ON.
Solution: Set multi-meter to Diode mode. Connect positive probe to center pin of charging port & the negative probe to USB ground. Reading should be OL (good). Connect negative probe to center pin of charging port & the positive probe to USB ground. Reading should be 0.9 volts (good). On this video after the laptop has been opened, the negative cable on charging port showed that it had come off.
Acer Aspire 5742
Problem: No power, PC won't turn on
Diagnostic: With multi meter set on DIODE mode, place positive probe to center pin of charging port, while the negative probe on USB ground. Reading on the meter should show OL (good). Then reverse the probes, negative probe on center pin of charging port, positive probe on USB ground, reading on meter should show 0.9 volts (good). If meter reading here shows OL, that means an open circuit or a break on the circuit.
Solution: After opening the back cover of PC, and a close inspection of the charging port. The red cable on the positive pin was no longer soldered.
Acer Aspire F5-571
Problem: No power, dead
Solution: Once back cover is removed, disconnect battery, remove BIOS battery & short the Bios battery pins.
Dell Inspiron 7520
Problem: PC won't turn on - dead
Diagnostic: After removing back cover, the charging port pins were protruding from its casing/enclosure.
Solution: Use hot glue to fix problem.
Dell Inspiron N5040
Problem: PC won't turn on - dead
Diagnostic: 19 volts present on all test points. The suspected power-on switch also had its 3.3 volts.
It was after testing the switch for the 3.3 volts that activated the laptop to turn on. When keyboard was re-installed the PC failed to turn On again. Keyboard was shorted.
Solution: Replaced keyboard.
Dell Latitude E7240
NOTE: This laptop is extremely hard to remove the mother board.
Problem: Laptop won't power on - dead PC.
Diagnostic: After removing back cover, 19 volts was present on the charging connector. There was no 3.3 volts on BIOS chip. No 3.3 volts on power button as well.
Solution: Remove PC battery, remove BIOS battery & short BIOS battery pins. Remove RAM memory & re-seat.
NOTE: Upon putting mother board back, it was discovered fan was not spinning although it had the 5 volts. Disconnected the data cable & tap from a 3.3 volts (search for a 3.3 volts that would not be on all the time) to run the fan. With this modification fan would always be on when PC is turned on.
Samsung NP-300E 5C
Problem: Laptop won't power on. No light.
Solution: Set multi meter to DCV & trace the 19 volts starting at charging port, fuses, and all the way to the 2 switches IC chips. The 19 volts from the output pins of the 1st switch IC chip is missing. No 19 volts as well going to the input & output of the 2nd IC chip. This indicates that the 1st IC chip could be open or shorted to ground. Charger was removed. At this point 19 volts from bench power supply was applied on the input & output pins of 1st chip to determine if there was a short. The current being applied shows zero amps reading, which means there's no current going to the ground. In this particular case, there's no short to ground but an open circuit on the 1st IC chip. Removing the 1st IC chip & bridging the contacts from input to output would be the fix.
Samsung RV-511
Problem: Will not power up.
Diagnostic: Set multi meter to Diode Mode. Connect negative probe to ground & positive probe to center pin of charging port. Correct meter reading should be OL. Next connect negative probe to middle pin of charging port & positive probe to ground. Correct meter reading should be 0.9 volts. If this reads OL, it's indicative of an Open circuit. In this case both test points showed OL.
Upon inspection of the mother board, positive pin on charging port has lost its connection to the board.
Apple Ipad
Problem: Color of screen is blue
Diagnosis: Data pins may not be making proper contacts to connector.
Solution: Bend lightly the 2 shorter ends of tablet.
Apple iPAD Air
Problem: Slow charging or no charging
Solution: Connect unit to USB meter. Connect unit to charger. Then press both Home button & Power On button simultaneously while monitoring the USB meter. Repeat process until you see the amps increase to 1.0 amps or higher.
Apple iPAD 3
Problem: No power & not charging
Solution: Remove digitizer & screen. Found charging connector disconnected. Take voltage reading of battery. Battery reading was 3.3 volts & amps reading was low. Induced current from bench power supply to battery with 3 amps. After a few seconds, USB meter showed a charging current of 1.9 amps from the unit's charger.
JVC tv Model: LT-22DG52J
Problem: No power
Diagnosis: One of the diodes in power supply section is shorted.
Solution: Remove shorted diode. Apply heat transfer pads (will serve as heat sink/transfer) on the 2 remaining diodes in parallel with the faulty one.
Toshiba Satellite Pro C50
Problem: No power. Won't switch on.
Solution: Remove battery, BIOS battery, short bios battery pins, remove & reseat RAM.
Toshiba Satellite C655D-S5518
Problem: BIOS password
Solution: Make a jumper wire. Remove battery, hard drive & keep only one RAM memory. Bridge B500 points (right beneath the RAM memory) while booting up PC. Disconnect power. Reinstall HD & RAM & turn on PC.
Toshiba PRO R50-B-12N Laptop
Problem: PC won't switch ON
Diagnosis: 19 volts is present. Check voltage on power switch - it should have 3.3 volts.
Check power switch itself if opening and closing. Check solder points. Short power switch to ground to test. If all checks OK & still would not power on the likely problem would be the Hall Sensor (magnetic switch) right next the button switch.
HP Pavillion DV5 (Black screen, BIOS corrupted)
Symptoms: Black screen, flashing caps & num-lock
Diagnostics:
LEDs blink 1x - CPU not functional
LEDs blink 2x - BIOS corruption failure
LEDs blink 3x - Memory module (error not functional)
LEDs blink 4x - Graphics (controller not functional)
LEDs blink 5x - System board (general system board failure)
LEDs blink 6x - BIOS authentication failure
Solution: Remove battery. Press & hold On-Off switch for 1 minute.
Connect power adapter (without the battery) and turn on PC
Remove RAM memory chips (if more than 1). Reconnect one at a time.
Connect power adapter (without the battery) and turn on PC
Remove Keyboard
Connect power adapter (without the battery) and turn on PC
HP Probook 450G2 (No picture on screen)
Diagnosis: Fault was found after removing KB & removing cable connectors of all devices (power button, speaker cable, touch pad cable, mouse, and card reader cable) one by one. Mouse/Touch pad was the culprit.
Solution: Cleaned mouse/touch pad assembly but touch pad no longer works after repair. The picture on screen however was resolved.
