Working principle of the voltage regulator - LED TV backlights

LED TV back light led voltage regulator working  

There are large arrays of LEDs located behind the LCD panel in a typical LCD TV LED back-lighting system as shown in Figure below . In this array are a large number of parallel channels of LEDs connected in series depending on the size of the TV and the type of back-lighting, for example edge back-lighting (less LEDs but more in series) or direct back-lighting (more LEDs in parallel) . The LED voltage (VLED) is provided by the White LED Back-light Driver Board to each LED channel and is regulated to a level needed by the highest voltage required to maximize the light output of each LED string .

Depending upon the power supply requirements determined by the number of LEDs in the string or grouping of parallel LED strings, the up-stream power source for the LED back-light driver board may be a DC/DC step-up boost converter, a DC/DC step-down converter or more commonly an AC/DC converter . In the case where supply voltage is lower than the required VLED, a step-up boost converter will be used . As an example, a LED boost converter LED back-lighting system will be described in detail in this paper for a direct back-lighting application, however the theory of operation will also apply to both the step-down converter and AC/DC converter situation.

LED Forward Current (IF) vs. Forward Voltage (VF)

High brightness LEDs used in LCD backlighting require high LED current which also equates to higher LED forward voltage . A typical relationship between TV backlight LED forward current (IF) and forward voltage (VF) is illustrated in Figure below. For example, if a user wants to set the LED current to 80mA maximum, a minimum of 3 .65V forward voltage must be provided to each LED in the string . If the power supply can only provide 3 .6V to each LED, then the maximum LED current is limited to 74mA .

Simplified LED Backlight LCD TV Block Diagram and Direct-type LED Array.

Typical LED Forward Current (IF) vs. Forward Voltage (VF).

 LED String with a Current Sink

Figure below  shows an LED backlight string with a controller which sets the brightness level with current sinks . VCS must be large enough in order for the current sink to operate properly . The lowest VCS of all of the LED strings will be the LED string with the largest composite forward voltage . The regulated VLED must be greater than VCS plus the highest composite LED forward voltage . If this condition is met, all the strings will have VCS greater than the dropout voltage (see the Dropout Voltage section of this document) and thus all current sinks will operate properly . In Figure 4, the LEDs in Ch . 1 (black) have a VF equal to 3 .5V and the LEDs in Ch . 2 have VF equal to 3 .2V . So if the highest voltage condition is met, each LED current sink will have sufficient headroom to provide accurate current to set the light output correctly . If VLED is regulated too low, the highest voltage LED string will be out of regulation and enter dropout, minimizing output current . On the other hand, if VLED is regulated too high, each LED string will have more than enough regulated voltage and good output current accuracy but unnecessary power will be dissipated across the current sink, resulting in extra power and heat dissipation.

Series LED String with Current Sink Control.

LED Array, 16 Channels of 10 LEDs Connected in Series.

 The LEDs in this example need 70mA to effectively backlight the LCD panel, but the Ch .1 LEDs have a higher VF than Ch . 2, requiring 35V to get 70mA .

 Boost Converter Driving LED Array

In a system where supply voltage (VIN) is lower than VLED, a step-up boost converter is used to provide power to the LED strings . As shown in Figure bellow, the output voltage of the boost converter drives all the LED strings . The feedback signal CSFBO connected to CSFB on the boost converter provides the lowest VCS level from all the LED strings and also controls how the VLED voltage is regulated . When the CSFB voltage is lower than the dropout voltage that is necessary for the LEDs to operate correctly, the stepup converter will boost the VLED level . However, when the CSFB voltage is higher than the dropout voltage, the step-up converter will stop boosting VLED . During this time, the LED current is provided by the boost output capacitor (C5) . This boost is set as a forced PWM system, so the pass switch (T1) will turn on with a minimum on-time (unless current limit or OVP is reached) to provide output current to the LEDs as well . At some point when the required LED current is higher than the current provided by the boost capacitor and the minimum on-time of T1, the VLED will start to drop and CSFB will go below the dropout voltage . At that time, the step-up converter will start boosting the VLED voltage level . Normal operation of the AAT2404 and AAT2403 is shown in the scope shots in Figures.The OVP setting on the boost is calculated to be at least 10% greater than the total forward voltage of each LED string plus the minimum VCS .

Example LED Back-light with Boost Controlled VLED.

Normal Operation of AAT2404 and AAT2403 with all Current Sinks (CS) in the AAT2403 set to 100mA, 80% DOT Correction (80mA) and 50% Gray Scale, No Delay.

While all CS are OFF, the VOUT level of the AAT2404 is at the OVP level . While all CS are ON, the VOUT level of the AAT2404 is regulated to the voltage required for the LEDs to sink 80mA

in the AAT2403 set to 100mA, 50% DOT Correction (50mA) and 50% Gray Scale, No Delay.

While all CS are OFF, the VOUT level of the AAT2404 is at the OVP level . While all CS are ON, the VOUT level of the AAT2404 is regulated to the voltage required for the LEDs to sink 50mA .

Normal Operation of AAT2404 and AAT2403 while AAT2404 is being set to 100mA,

100% PWM Duty Ratio (fully turned on at 100mA).

Dropout Voltage

The dropout voltage is the voltage level when the current sinks in the backlight controller start to go out of current regulation . This is also the voltage level used as the reference for the power supply converter . For a current sink to operate with good accuracy, VCS has to be greater than the dropout voltage . As shown in Figure 9 for the AAT2403, the dropout voltage will be different depending upon the maximum current requirement and is proportional to the current sink current (ILED) and RSET value (R2 in Figure 5) . When using the AAT2404 boost converter, the same values of RSET should be used for both AAT2403 and AAT2404 . However for a stand alone power supply working with AAT2403, the dropout voltage is the reference voltage for the converter which should be determined by the RSET value .

Dropout Voltage is the VCS Voltage Level Point where ILED starts to Roll Off

(100% PWM Duty Ratio and 100% DOT).

Startup

During startup, since LED strings are not yet turned on, the CSFB voltage is at 0V, so the boost converter will start stepping up VLED . In the case of the AAT2404, the startup voltage soft starts to 90% of the OVP voltage . This provides enough voltage level for VLED when the first LED string turns on . The boost converter will not step up full VLED until the CSFB voltage is below the reference (dropout) voltage .

Sample and Hold During ON/OFF

In some systems it is desirable to maintain the operating LED voltage when the LED current sinks are OFF . When the LEDs are OFF, the voltage across the LED string decreases . When the LED string turns off, the current sink voltage will rise . Without a sample and hold technique, the LED voltage will regulate down in order to drive the current sink voltage to the regulation point even though the LED string is OFF . Since there is no power consumed when the LED string is off, regulating the current sink voltage during the OFF time of the LED string is unnecessary . A potentially unwanted effect of regulating the LED voltage during the OFF time is that additional time is necessary to establish the proper LED voltage when the current sink is turned back on as the LED voltage slews to the required voltage level . During this time, the current in the LED string will not be regulated and will tend to be less than the final desired LED current level . For the AAT2404, when the external current sinks are ON, the CSFB is regulated to the internal reference (dropout) voltage . When the external current sinks are OFF or CSFB voltage is greater than an internal set voltage (2 .5V), the LED voltage is determined by the voltage level left on the on the compensation capacitor (C3 in Figure ) which has been disconnected from the feedback loop . During this OFF time, since the inductor current is proportional to the compensation capacitor’s voltage, VLED will not decrease and will be either held or increase slightly until required to turn on the LEDs . In the extreme case when no LED current is drawn, VLED could be charged as high as OVP, which will provide enough voltage level headroom for the next current sink to turn back on . In this case, VLED will operate between OVP and the minimum VLED . This will eliminate the unwanted effect of converter response time and current slewing when the LED is turned back on again .

To disable the sample and hold feature on the AAT2404, a 10k resistor can be inserted from CSFB to ground . VLED will be regulated even when the current sinks are OFF, causing current slewing during turn on .

TV LED Backlight Drivers and Related Devices

The following devices have a Voltage mode CSFBO output (and input for cascading ICs):
AAT2401
AAT2402S
AAT2403
The voltage mode feedback of each of these ICs is intended for direct interfacing to the AAT2404 boost converter or in master/slave operation with the AAT2400 or AAT2402M .
When using these devices as a single driver or if the device is the first IC in a cascaded chain of ICs, then the CSFBI input pin should be terminated to VCC to remove it from the system . The reference voltage (dropout voltage) is unique to each external power supply and can be determined as described in the Dropout Voltage.

Lenovo Flex 3 – Disassembling procedure – How to test the battery charger – How to remove the cover – How to remove the battery pack

To verify a symptom, follow the steps below:
1. Turn off the computer.
2. Connect the AC adapter.
3. Make sure that power is supplied when you turn on the computer.
4. Turn off the computer.
5. Disconnect the AC adapter.
6. Make sure that the battery pack supplies power when you turn on the computer.
If you suspect a power problem, see the appropriate power supply checkout:
“Checking the AC adapter”
“Checking operational charging”
Checking the AC adapter
You are here because the computer fails only when the AC adapter is used.
If the power-on indicator does not turn on, check the power cord of the AC adapter for correct continuity and installation.
To check the AC adapter, follow the steps below:
1. Unplug the AC adapter cable from the computer.
2. Measure the output voltage at the plug of the AC adapter cable. See the following figure:

Note: Output voltage for the AC adapter pin No. 2 may differ from the one you are servicing.

3. If the voltage is not correct, replace the AC adapter.
4. If the voltage is acceptable, do the following:
Replace the system board.
Note: Noise from the AC adapter does not always indicate a defect.
Checking operational charging
To check whether the battery charges properly during operation, use a discharged battery pack or a battery pack that has less than 50% of the total power remaining when installed in the computer.

Perform operational charging. If the battery status indicator or icon is not lit, remove the battery pack and let it return to room temperature. Reinstall the battery pack. If the charge indicator or icon is still off, replace the battery pack. If the charge indicator is still not lit, replace the system board.

Restore of factory default

The Lenovo Flex 3-1120/Flex 3-1130 computer comes with pre-installed OneKey Recovery System.In order to save application files and the initial backed up files of the system, the hard disk in a Lenovo computer includes a hidden partition when it is shipped. If you need to restore the system to the point of your first boot up, just enter Lenovo OneKey Recovery System and run System Recovery.

Disassembling procedure 

How to remove Base cover
Remove the screws 1. Then remove the base cover 2.

How to remove Battery pack

Unplug the battery connector 1 and remove the screws 2. Then remove the battery pack in the direction shown by arrow 3.

How to remove Hard disk drive

Detach HDD connector in the direction shown by arrow 1.

Remove the frame fixing screws 2.

Remove the hard disk drive in the direction shown by arrow 3

Sony COMPACT DISC DECK RECEIVER - SONY HCD-GTR33 - GTR55 - GTR77 – Test mode - panel test procedure – cold reset – Factory preset – power amplifier schematic diagram

SONY HCD-GTR33 - GTR55 - GTR77: TEST MODE

PANEL TEST MODE
This mode is used to check the fluorescent indicator tube, LEDs, keys, [MASTER VOLUME] jog, [OPERATION DIAL] jog, model, destination and software version.
Procedure:
1. Press [STOP] button, [METER MODE] button and [DISC SKIP/ EX-CHANGE] button simultaneously.
2. All LEDs and segments in fluorescent indicator tube are lighted up.
3. When you want to enter to the software version display mode, press [DISC 1] button. The model information appears on the fluorescent indicator tube.
# “GVX 1S” is shown for MHC-GTR33.
# “GVX 3S” is shown for MHC-GTR55.
# “GVX 4S” is shown for MHC-GTR77.
Press [DISC 1] button again to view the destination information.
4. During the destination information display, press [DISC 1] button. Each time [DISC 1] button is pressed, the fluorescent indicator tube shows the version of each category software in the following sequence: SC, MTK (DMB Board firmware version), GC, SYS, CD, CDMA, CDMB, ST, TC TA, TM , MTR (METER) and return back to model information display.
5. When [DISC 3] button is pressed while the version numbers are being displayed except model and destination, the date of the software creation appears. When [DISC 3] button is pressed again, the display returns to the software version display. When [DISC 1] button is pressed while the date of the software creation is being displayed, the date of the software creation is displayed in the same order of software version display.
6. Press [DISC 2] button, the key check mode is activated.
7. In the key check mode, the fluorescent indicator tube displays “K 0 V0”.
Each time a button is pressed, “K” value increases. However, once a button has been pressed, it is no longer taken into account. “V” value increases in the manner of 0,1, 2, 3 ... if [MASTER VOLUME] knob is turned clockwise, or it decreases in the manner of 0, 9, 8,7 ... if [MASTER VOLUME] knob is turned counterclockwise.
8. When [DISC SKIP/EX-CHANGE] button is pressed after all LEDs and segments in fluorescent indicator tube light up, alternate segments in fluorescent indicator tube and LEDs would light up. If you press [DISC SKIP/EX-CHANGE] button again, another half of alternate segments in fluorescent indicator tube and LEDs would light up. Pressing [DISC SKIP/ EX-CHANGE] button again would cause all segments in fluorescent indicator tube and LEDs light up.
9. To release from this mode, press three buttons in the same manner as step 1, or disconnect the power cord.

COMMON TEST MODE
This mode is used to check operations of the Amplifier section.
Procedure:
To enter Common Test Mode
1. Press [STOP] button, [METER MODE] button and [OPEN/
CLOSE] button simultaneously.
2. The CD ring indicators flash on the fluorescent indicator tube.
The function is changed to AUDIO and the volume is changed
to VOLUME MIN.
Check of Amplifier
1. Press [EQ BAND/SURROUND] button repeatedly until a message “GEQ MAX” appears on the fluorescent indicator tube. GEQ increases to its maximum.

2. Press [EQ BAND/SURROUND] button repeatedly until a message “GEQ MIN” appears on the fluorescent indicator tube. GEQ decreases to its minimum.
3. Press [EQ BAND/SURROUND] button repeatedly until a message “GEQ FLAT” appears on the fluorescent indicator tube. GEQ is set to flat.
4. When the [MASTER VOLUME] knob is turned clockwise even slightly, the sound volume increases to its maximum and a message “VOLUME MAX” appears on the fluorescent indicator tube.
5. When the [MASTER VOLUME] knob is turned counterclockwise even slightly, the sound volume decreases to its minimum and a message “VOLUME MIN” appears on the fluorescent indicator tube.
To release from Common Test mode
1. To release from this mode, press [STANDBY] button.
2. The cold reset is enforced at the same time.

COLD RESET
The cold reset clears all data including preset data stored in the EEPROM to initial conditions. Execute this mode when returning the set to the customer.
Procedure:
1. Press [STANDBY] button to turn on the system.
2. Press [STOP] button, [ENTER] button, and [STANDBY] button simultaneously.
3. “COLD RESET” appears on the fluorescent indicator tube.
After that, the fluorescent indicator tube becomes blank for a while, and the system is reset.
VACS ON/OFF
This mode is used to switch ON and OFF the VACS (Variable Attenuation Control System).
Procedure:
1. Press [STANDBY] button to turn on the system.
2. Press [STOP] button, [RETURN], and [DISPLAY] button simultaneously. The message “VACS OFF” or “VACS ON” appears on the fluorescent indicator tube.

TUNER STEP CHANGE
The step interval of AM channels can be toggled between 9 kHz
and 10 kHz.
Procedure:
1. Press [?/1 STANDBY] button to turn on the system.
2. Press [TUNER/BAND] button repeatedly to select the “AM”.
3. Press [?/1 STANDBY] button to turn off the system.
4. Press [ENTER] button and [STANDBY] button simultaneously. The system turns on automatically. The message “AM 9K STEP” or “AM 10K STEP” appears on the fluorescent indicator tube and thus the channel step is changed.
CD SHIP MODE (WITH MEMORY CLEAR)
This mode moves the optical pick-up to the position durable to
vibration and clears all data including preset data stored in the EEPROM to initial conditions during the next AC-In. Use this mode
when returning the set to the customer after repair.
Procedure:
1. Press [STANDBY] button to turn on the system.
2. Select CD function.
3. Press [STOP] button, [OPEN/CLOSE] button and [STANDBY] button simultaneously. The system turns off automatically.
4. After the “STANDBY” blinking display finishes, a message
“MECHA LOCK” is displayed on the fluorescent indicator tube and the CD ship mode is set.

CD SHIP MODE (WITHOUT MEMORY CLEAR)
This mode moves the optical pick-up to the position durable to vibration. Use this mode when returning the set to the customer after repair.
Procedure:
1. Press [ STANDBY] button to turn on the system.
2. Select CD function.
3. Press [DISC SKIP/EX-CHANGE] button and [STANDBY] button simultaneously. The system turns off automatically.
4. After the “STANDBY” blinking display finishes, a message “MECHA LOCK” is displayed on the fluorescent indicator tube and the CD ship mode is set.
CD TRAY LOCK MODE
This mode let you lock the disc tray. When this mode is activated, the disc tray will not open when [OPEN/CLOSE] button or [DISC SKIP/EX-CHANGE] button is pressed. The message “LOCKED” will be displayed on the fluorescent indicator tube. This mode only applied when there is disc(s) on the tray.
Procedure:
1. Press [STANDBY] button to turn on the system.
2. Select CD function.
3. Press [STOP] button and [OPEN/CLOSE] button simultaneously and hold down until “LOCKED” or “UNLOCKED” displayed on the fluorescent indicator tube (around 5 seconds).
FACTORY PRESET
This mode is use to load all the factory use preset frequencies into FM 1-FM 20 and AM 1-AM 10. Originally, frequency of FM 1-FM 20 and AM 1-AM10 are set to the minimum frequency.
Procedure:
1. Press [STANDBY] button to turn on the system.
2. Press [EQ BAND/SURROUND] button, [STOP] button, and [DISC 1] button simultaneously and the message “FACTORY” appears on the fluorescent indicator tube. The function is changed to TUNER automatically.
VACS DISPLAY
This mode is used to check the VACS level.
Procedure:
1. Press [STANDBY] button to turn on the system.
2. Press [ERASE] button, [x] button and [ENTER] button simultaneously.
3. The fluorescent indicator tube displays “V0 AP0”. “V” represents Conventional VACS (Triggered by signal level) “AP” represents AP VACS (Abuse Protection Variable Attenuation Control System)
To release from VACS display mode
To release from this mode, do the step (2) again.
METER SWITCH TOUCH COUNT DISPLAY
This mode is used to display the total count of meter pointer touch initial switch and max switch.
Procedure:
1. Press [STANDBY] button to turn on the system.
2. Press [STOP] button, [ENTER] button and [DISPLAY] button simultaneously.
3. The fluorescent indicator tube displays “IxxxxxMyyyyy”. “I” represents the Initial Switch touch. “xxxxx” represents the total count of Initial Switch touch. (Maximum Value of “xxxxx” = 65535) “M” represents the Max Switch touch. “yyyyy” represents the total count of Max Switch touch. (Maximum Value of “yyyyy” = 65535)
To release from Meter Switch Touch Count Display Mode. To release from this mode, do the step (2) again. The fluorescent indicator tube displays “MODE OUT”.

POWER AMPLIFIER CIRCUIT DIAGRAM::STK416-120-E - STK416-130-E - STK433-320-E

METER TEST MODE

This mode is used to check the meter device.
Procedure:
1. Press [STANDBY] button to turn on the system.
2. Press [STOP ] button, [ENTER] button and [METER MODE] button simultaneously.
3. Meter Backlight LEDs, Meter Pointer LEDs, Power Illuminator LEDs and fluorescent indicator tube are lighted up.
4. When you want to perform count total step from Initial
Switch to Max Switch operation mode, press [>> / >>I / TUNING + ] button. The meter pointer will move from Initial Switch to Max Switch and finally move back to the middle position. The total step count information appears on the fluorescent indicator tube. “xxx STP yy” is shown. “xxx” represents the total step.
(Value of “xxx” should between 430 steps to 470 steps) “yy” represents the status of total step count.
(If total step between 430 steps to 470 steps, “yy” is OK, Else “yy” is NG)
5. When you want to perform count total step from Max Switch to Initial Switch operation mode, press [<< / I<< / TUNING – ] button. The meter pointer will move from Max Switch to Initial Switch and finally move back to the middle position. The total step count information appears on the fluorescent indicator tube. “xxx STP yy” is shown. “xxx” represents the total step.
(Value of “xxx” should between 430 steps to 470 steps) “yy” represents the status of total step count.
(If total step between 430 steps to 470 steps, “yy” is OK, else “yy” is NG)
To release from Meter Test Mode.
To release from this mode, do the step (2) again.
The fluorescent indicator tube displays “TST MODE OUT”.

CDM AGING MODE
This mode is used to display the total count of all disc playing.
Procedure:
1. Press [STANDBY] button to turn on the system.
2. Select CD function and All DISC play mode
3. Put discs on all trays and close the tray.
4. Press [GROOVE] button, [STOP] button and [RETURN] button simultaneously.
5. The fluorescent indicator tube displays Aging Display “AG xxxx/yyyy”. “xxxx” represents the error counter
(Maximum Value of “xxxx” = 9999) “yyyyy” represents the cycle counter (Maximum Value of “yyyy” = 9999)
6. Press [<</ I<< / TUNING – ] or [ >> / >>I / TUNING + ] to search for Aging History Error Display
The fluorescent indicator tube displays “Mx E1E2E3E4”. x: error history number
E1: Loading sequence JCP high
E2: Loading sequence JCP low
E3: Loading operation JCP
E4: Cam position operation JCP
7. Press [RETURN] to Aging Display
To release from CDM Aging Mode.
To release from this mode, press [STANDBY] button or perform COLD RESET operation.

HP Split 13 x2 – Disassembling procedure – How to remove the batteries – How to remove the base cover – How to replace the RTC battery – How to update the BIOS

HP Split 13 x2 disassembling procedure 

How to remove Base enclosure

Before disassembling the keyboard dock, follow these steps:
1. Shut down the keyboard dock. If you are unsure whether the computer is off or in Hibernation, turn the computer on, and then shut it down through the operating system.
2. Disconnect all external devices connected to the computer.
3. Disconnect the power from the computer by first unplugging the power cord from the AC outlet and then unplugging the AC adapter from the computer.
4. Disconnect the tablet from the keyboard dock
Remove the base enclosure:
1. Remove the two upper rubber feet (2), and then the two Phillips PM2.5×6.0 screws (3) underneath.
2. Separate and release the base enclosure (4) from the dock.

How to remove Hard drive

Before removing the hard drive, follow these steps:
1. Shut down the computer. If you are unsure whether the computer is off or in Hibernation, turn the computer on, and then shut it down through the operating system.
2. Disconnect all external devices connected to the computer.
3. Disconnect the power from the computer by first unplugging the power cord from the AC outlet and then unplugging the AC adapter from the computer.
4. Disconnect the tablet from the keyboard dock
5. Remove the base enclosure
6. Disconnect the battery cable.

Remove the hard drive:

1. Remove the three Phillips PM2.0×5.0 screws (1) that secure the hard drive to the dock.
2. Disconnect the hard drive cable (2) from the hard drive.

3. Remove the hard drive from the dock (3).

How to remove Hinge assembly

Before removing the hinge, follow these steps:
1. Shut down the computer. If you are unsure whether the computer is off or in Hibernation, turn the computer on, and then shut it down through the operating system.
2. Disconnect all external devices connected to the computer.
3. Disconnect the power from the computer by first unplugging the power cord from the AC outlet and then unplugging the AC adapter from the computer.
4. Disconnect the tablet from the keyboard dock
5. Remove the base enclosure
6. Disconnect the battery cable.

 Remove the hinge assembly:

1. Remove the four Phillips PM2.5×5.0 screws (1) that secure the hinge to the dock.
2. Disconnect the cables from each side of the dock (2).

3. Lift the hinge assembly (3) from the dock.

How to remove Battery

Before removing the battery, follow these steps:
1. Shut down the computer. If you are unsure whether the computer is off or in Hibernation, turn the computer on, and then shut it down through the operating system.
2. Disconnect all external devices connected to the computer.
3. Disconnect the power from the computer by first unplugging the power cord from the AC outlet and then unplugging the AC adapter from the computer.
4. Disconnect the tablet from the keyboard dock
5. Remove the base enclosure

6. Disconnect the battery cable.

Remove the battery:

1. Remove the six Phillips PM2.0×4.0 screws (1) that secure the battery to the dock.
2. Remove the battery (2) from the dock.

How to remove Display rear cover

Before removing the display rear cover, follow these steps:
1. Shut down the computer. If you are unsure whether the computer is off or in Hibernation, turn the computer on, and then shut it down through the operating system.
2. Disconnect all external devices connected to the computer.
3. Disconnect the power from the computer by first unplugging the power cord from the AC outlet and then unplugging the AC adapter from the computer.
4. Disconnect the tablet from the keyboard dock
Remove the display rear cover:
1. Remove the two rubber screw covers (1) and two Phillips PM2.0×3.0 screws (2) that secure the cover to the tablet.
2. Using the slot in the cover, lift the cover off the tablet (3)

How to remove Battery cable

You do not have to remove the internal battery before removing several internal components. However, if you leave the battery installed while removing components, be sure to disconnect the battery cable from the system board to remove power from internal components.
Before disconnecting the battery cable, follow these steps:
1. Shut down the computer. If you are unsure whether the computer is off or in Hibernation, turn the computer on, and then shut it down through the operating system.
2. Disconnect all external devices connected to the computer.
3. Disconnect the power from the computer by first unplugging the power cord from the AC outlet and then unplugging the AC adapter from the computer.
4. Disconnect the tablet from the keyboard dock
5. Remove the display rear cover
Disconnect the battery cable:
Lift the tape on top of the connector (1), and then disconnect the battery cable from the system board
connector (2).

How to remove RTC battery

Before removing the RTC battery, follow these steps:
1. Shut down the computer. If you are unsure whether the computer is off or in Hibernation, turn the computer on, and then shut it down through the operating system.
2. Disconnect all external devices connected to the computer.
3. Disconnect the power from the computer by first unplugging the power cord from the AC outlet, and then unplugging the AC adapter from the computer.
4. Disconnect the tablet from the keyboard dock
5. Remove the display rear cover
6. Disconnect the battery cable
Remove the RTC battery:
1. Use a screwdriver to loosen the battery from the socket (1).
2. Lift the battery from the socket (2).

How to remove Battery

The tablet includes an internal battery.
Before removing the battery, follow these steps:
1. Shut down the computer. If you are unsure whether the computer is off or in Hibernation, turn the computer on, and then shut it down through the operating system.
2. Disconnect all external devices connected to the computer.
3. Disconnect the power from the computer by first unplugging the power cord from the AC outlet and then unplugging the AC adapter from the computer.
4. Disconnect the tablet from the keyboard dock
5. Remove the display rear cover 
6. Disconnect the battery cable 
1. Disconnect the HT cable (1).
2. Remove the Phillips broad-head PM2.0×3.0 screw (2) and the four Phillips PM2.0×5.0 screws (3) that secure the battery to the tablet.
3. Remove the battery (4) from the tablet.

BIOS update

1. From the Start screen, type support, and then select the HP Support Assistant app.
2. Click Updates and tune-ups, and then click Check for HP updates now.
3. Follow the on-screen instructions.
4. At the download area, follow these steps:
a. Identify the most recent BIOS update and compare it to the BIOS version currently installed on your computer. If the update is more recent than your BIOS, make a note of the date, name, or other identifier. You may need this information to locate the update later, after it has been downloaded to your hard drive.
b. Follow the on-screen instructions to download your selection to the hard drive.
If the update is more recent than your BIOS, make a note of the path to the location on your hard drive where the BIOS update is downloaded. You will need to access this path when you are ready to install the update.

BIOS installation procedures vary. Follow any instructions that are displayed on the screen after the download is complete. If no instructions are displayed, follow these steps:
1. From the Start screen, type e, and then select File Explorer.
2. Click your hard drive designation. The hard drive designation is typically Local Disk (C:).
3. Using the hard drive path you recorded earlier, open the folder on your hard drive that contains the update.
4. Double-click the file that has an .exe extension (for example, filename.exe).
The BIOS installation begins.
5. Complete the installation by following the on-screen instructions.

How to replace and reset lamp – BenQ MX613ST, BenQW1080, BenQW1070 projectors

BenQ MX613ST

Replacing the lamp

• To reduce the risk of electrical shock, always turn the projector off and disconnect the power cord before changing the lamp.

• To reduce the risk of severe burns, allow the projector to cool for at least 45 minutes before replacing the lamp.

• To reduce the risk of injuries to fingers and damage to internal components, use caution when removing lamp glass that has shattered into sharp pieces.

• To reduce the risk of injuries to fingers and/or compromising image quality by touching the lens, do not touch the empty lamp compartment when the lamp is removed.

• This lamp contains mercury. Consult your local hazardous waste regulations to dispose of this lamp in a proper manner.

• To assure optimal performance from the projector,it is recommended that you purchase a qualified projector lamp for lamp replacement.

• If lamp replacement is performed while the projector is suspended upside-down from the ceiling, make sure that no one is underneath the lamp socket to avoid any possible injury or damage to the human eyes caused by fractured lamp.

1. Turn the power off and disconnect the projector from the power outlet. If the lamp is hot, avoid burns by waiting for approximately 45 minutes until the lamp has cooled.

2. Loosen the screw(s) that secures the lamp cover on the side of the projector until the lamp cover loosens

3. Remove the lamp cover from the projector.

• Do not turn the power on with the lamp cover removed.

• Do not insert your fingers between the lamp and the projector. The sharp edges inside the projector may cause injuries.

4. Disconnect the lamp connector from the projector as illustrated.

5. Loosen the screw that secures the lamp.

6. Lift the handle so that it stands up

7. Use the handle to slowly pull the lamp out of the projector.

• Pulling it too quickly may cause the lamp to break and scatter broken glass in the projector.

• Do not place the lamp in locations where water might splash on it, children can reach it, or near flammable materials.

• Do not insert your hands into the projector after the lamp is removed. If you touch the optical components inside, it could cause color unevenness and distortion of the projected images.

8.  Lower the new lamp

9. Tighten the screw that secures the lamp.

10. Ensure the handle is fully laid flat and locked in place.

11. Reconnect the lamp connector.

• Loose screw may cause a bad connection, which could result in malfunction.

• Do not over tighten the screw

12. Replace the lamp cover on the projector.

13. Tighten the screw(s) that secures the lamp cover.

• Loose screw may cause a bad connection, which could result in malfunction.

• Do not over tighten the screw.

14. Connect the power and restart the projector. Do not turn the power on with the lamp cover removed.

Resetting the lamp timer

15. After the start up logo, open the On-Screen Display (OSD) menu. Go to the SYSTEM SETUP: Advanced> Lamp Settings menu. Press MODE/ENTER. The Lamp Settings page displays. Highlight Reset Lamp Timer. A warning message is displayed asking if you want to reset the lamp timer. Highlight Reset and press MODE/ENTER. The lamp time will be reset to “0”. Do not reset if the lamp is not new or replaced as this could cause damage.

BenQ W1080, W1070

Replacing the lamp

• To reduce the risk of electrical shock, always turn the projector off and disconnect the power cable before changing the lamp.

• To reduce the risk of severe burns, allow the projector to cool for at least 45 minutes before replacing the lamp.

• To reduce the risk of injuries to fingers and damage to internal components, use caution when removing lamp glass that has shattered into sharp pieces.

• To reduce the risk of injuries to fingers and/or compromising image quality by touching the lens, do not touch the empty lamp compartment when the lamp is removed.

• This lamp contains mercury. Consult your local hazardous waste regulations to dispose of this lamp in a proper manner. Status Message Install a new lamp for optimal performance. If the projector is normally run with Economics elected , you may continue to operate the projector until the next hour lamp warning appears. Press MODE/ENTER to dismiss the message. It is strongly recommended that you replace the lamp at this stage. The lamp is a consumable item. The lamp brightness diminishes with use. This is normal lamp behavior. You can replace the lamp whenever you notice that the brightness level has significantly diminished. Press MODE/ENTER to dismiss the message. The lamp MUST be replaced before the projector will operate normally. Press MODE/ENTER to dismiss the message.

1. Turn the power off and disconnect the projector from the power outlet. If the lamp is hot, avoid burns by waiting for approximately 45 minutes until the lamp has cooled.

2. Loosen the screw that secures the lamp cover on the side of the projector until the lamp cover loosens.

3. Remove the lamp cover from the projector.

• Do not turn the power on with the lamp cover removed.

• Do not insert your fingers between the lamp and the projector. The sharp edges inside the projector may cause injuries.

4. Loosen the screw that secures the lamp.

5. Lift the handle so that it stands up.

6. Use the handle to slowly pull the lamp out of the projector.

• Pulling it too quickly may cause the lamp to break and scatter broken glass in the projector.

• Do not place the lamp in locations where water might splash on it, children can reach it, or near flammable materials.

• Do not insert your hands into the projector after the lamp is  removed. If you touch the optical components inside, it could cause color unevenness and distortion of the projected images.

7. Lower the new lamp.

8. Tighten the screw that secures the lamp.

9. Ensure the handle is fully laid flat and locked in place.

• Loose screw may cause a bad connection, which could result in  Malfunction.

• Do not over tighten the screw.

10. Replace the lamp cover on the projector.

11. Tighten the screw that secures the lamp cover.

• Loose screw may cause a bad connection, which could result in malfunction.

• Do not over tighten the screw.

12. Connect the power and restart the projector.

Resetting the lamp timer

Do not reset the lamp timer if the lamp has not been replaced as this could cause damage.

13. After the start-up logo, press MENU/EXIT and then press / until the System Setup : Advanced menu is highlighted.

14. Press to highlight Lamp Settings and press MODE/ENTER. The Lamp Settings page displays.

15. Highlight Reset Lamp Timer and press MODE/ENTER. A warning message displays asking if you want to reset the lamp timer. Highlight Reset and press MODE/ENTER. The lamp time will be reset to "0".

JBL BASS 550 powered sub woofer test procedure

Equipment needed: The “Source” AM/FM turner/CD player with remote control, Function/signal generator/sweep generator.  

Multimeter.

Cable - Phono plugs (RCA) and speaker cables. 

RCA Y-cable

Subwoofer, General Function
1) Connect both right and left phono jack (RCA) inputs to signal generator and the “Source” Tape/Aux. input jacks. Use Y-cable if necessary from mono source.
2) Connect Bass550 subwoofer to the “Source” with 13 pin Din cable.

3) Plug in subwoofer, turn power switch on; red LED should light.
4) Turn on generator, adjust to 100 mV, 50 Hz.
5) Push “power” button on the “Source”, (display should now be active); press “Tape/Aux” button, adjust volume (on Source) so display reads “VOLUME 30”.
6) Turn up level control on subwoofer full clockwise.
7) LED on subwoofer should cycle to green; bass response should be heard and felt from port tube opening.

Subwoofer, Sweep Function
1) Follow steps 1-7 above, using a sweep generator as a signal source.
2) Sweep generator from 20Hz to 300Hz. Listen to the cabinet and drivers for anyrattles, clicks, buzzes or anyother noises. If any unusual noises are heard, remove driver and test.

Subwoofer, Driver Function
1) Remove one or both drivers from cabinet; remove + and - wire clips.
2) Check DC resistance of driver; it should be approximately 5.8 ohms.
3) Connect a pair of speaker cables to driver terminals.
Cables should be connected to an integrated amplifier fed by a signal generator. Turn on generator and adjust so that speaker level output is 4.0V.
4) Sweep generator from 20Hz to 1kHz. Listen to driver for any rubbing, buzzing, or other unusual noises.

System, General Function
1) Connect Bass 550 subwoofer to the “Source” with supplied 13 pin Din cable.
2) Attach all five satellite speakers to the supplied speaker cables, terminating in a molex connector plugged into the subwoofer.
3) Plug in Bass550 subwoofer, turn power switch on; red LED should light.
4) Push “power” button on the “Source”; (display should now be active).
5) Toggle “surround mode” button on front panel or with remote control until “NORMAL” appears.
6) Toggle “rear speaker” button on front panel until “REAR SPEAKERS” is displayed in upper left corner.
7) Adjust volume (on Source) so display reads “VOLUME 30”.
8) Using remote control, press “TONE” button.
9) White noise should be heard, cycling from Left, Center, Right and Rear speakers in succession.
10)Press “TONE” button again to halt test.

INFINITY RS-12 SUBWOOFER troubleshooting – Fuse blown – relay not closing

INFINITY RS-12 Troubleshooting; For all problems (except blowing fuses)

After amplifier removal from cabinet, pull back plastic cover to examine unit. It is usually not necessary to completely detach the cover from the amp assembly.
CHECK TO SEE THAT RELAYS ARE CLOSING NORMALLY AND CONTACTS ARE
CLOSING: (Power LED goes ON, two audible "clicks" are heard 2 - 5 seconds after power is turned on):

 1. Attach power cord, connect AC signal (with Y-cable) into low level inputs; 100 mV @ 100Hz or music signal. Turn UUT on.
To confirm Relay 101 (power supply) is functional, check voltage across relay coil (see drawing for location) for 19 - 21 VDC. Then check voltages across R105/R106. RS-10: 12 - 13 VDC; RS-12: 22 - 23 VDC. If voltage is considerably higher there is a short causing the entire power supply voltage to appear across R105/R106. Or if voltage is absent see "NEITHER RELAY IS CLOSING" below.
To confirm Relay 102 (speaker output) is functional, check voltage across relay coil (see drawing for location) for 19 - 21 VDC. Attach 2 - 4 O power resistor to output cable of UUT. Check voltage across R147 for less than 50 mVAC. Little or no voltage across R147 assures R102 contacts are closing normally. (See drawing for location of R147.) If voltage is absent from relay coil see "FIRST RELAY (RLA 101) IS CLOSING, SECOND RELAY (RLA 102) IS NOT CLOSING"

Neither relay is closing

1. Check to see if LED is on, if not check to see if line fuse is blown. Replace if necessary — if fuse blows again see section IV: "UNIT BLOWS FUSES". If line fuse is not blown and LED is not on, check all AC connections at terminals and condition of line thermistor (should have DCR of 9 - 12 O). Otherwise replace toroidal transformer if required.

2. If LED is on and 21 VAC is present at the amp board (blue & black wires), and if 19 - 21 VDC is present at Relay 101 coil but no "click" is heard and rest of unit does not energize, replace Relay 101.

3. If no DC voltage is present at Relay 101 coil, check DC voltage across C103/C105 for +/- 15 - 17VDC. If voltages are very low unplug ribbon connector to filter board and re-check. If voltage rises to correct value than one of two conditions exist: A. C102, C104 are shorted or defective (most likely), or B. There is a short on the filter board, probably IC 201 (LF 347N). Replace and re-test.
Note: IC sockets are recommended for the new IC's.

If after IC replacement only one correct voltage is present check/replace appropriate Zener diode (D108 for C103, D111 for C105). 4. If DC voltages across C103/C105 are correct and Relay 101 is not closing: A. Unplug ribbon cable attached to input board. B. Insert a 15k resistor into leads 5 & 8 of the unplugged female connector end. (See drawing) C. Turn on UUT. If Relay 101 still doesn't close, check condition of D130 with "diode check" function on DMM; if shorted, replace. If O.K. replace Q116. 5. If DC voltage is present at Relay 101 coil and if it still doesn't closes, replace Relay 101.

First relay (rla 101) is closing; second relay (rla 102) is not closing

1. Check for 21 volts across Relay 102 coil . If present, replace Relay 102.

2. If no voltage is present: Check DC voltage across R105/R106. If voltage is substantially higher than (12-13 volts for RS10; 22-23 volts for RS12) there is a short on the 16v circuit.

To troubleshoot

A. Unplug ribbon cable attached to input board.

B. Insert a 15k resistor into leads 5 & 8 of the unplugged female connector end.  

C. Turn on UUT, second relay may now turn on and R105/R106 voltages may be correct. If so, replace IC 201 on input board.

D. If voltage is still high check zener diode (D116 for R106), (D115 for R105) for voltage abnormalities. Forward bias of zener can be checked with "diode check" function on DMM in the circuit or by checking for +/- 16 volts across zeners when energized. If either diode is defective, replace.

3. If no voltage is present at Relay 102 and voltages are correct across R105/R106:

Check for +15-16 volts on pin 8 of IC 101 (LF 347N) on main amp board.

Check for +1.7 to 1.9 volts on pin 9.

Check for +8 volts on pin 10.
If any of the above voltages are abnormal

Check DC voltage across R116 (33KO). (See drawing for location) Less than 50mV should be present. If higher, relay will not energize. DC is coming through the amplifier section. Check and replace semiconductors as necessary.

If there is negligible voltage across R116, (normal condition) check junctions of Q102, Q103 with "diode check" function on DMM in the circuit. Replace if defective. If O.K., replace IC 101 (LF 347N) on main amp board.
If all voltages are correct on IC 101:

Check junction of D118 "diode check" function on DMM in the circuit. Replace if defective. If O.K., replace Q101.

Unit blows fuses

Two conditions are possible: UUT blows fuses instantly when power switch is thrown, or UUT blows fuses when power supply relay is energized (due to an input signal).

Unit blows fuses instantly with no input signal

Desolder, remove power supply wires from main amp board (blue & black). Replace fuse, power up unit again. If fuse blows, replace shorted toroidal power transformer.

Unit blows fuses immediately after first relay is energized

A. Problem is usually shorted output or driver transistor or diode semi-bridge on main amp board.

These consist of: 2SC 3856 / 2SA 1492 TO-218 package; BD 911/912 TO-220 package;  FEN 16 / FEP 16 TO-220 package

Note: First check condition of D102,103.

All junctions can be tested in the circuit with a "diode check" function on a DMM. If a short is found; however, remember some devices are in parallel and will have to be removed to confirm the short.

B. Occasionally the output transistors seem O.K. or after a replacements high currents will continue to blow fuses. The problem is probably with one of the biasing transistors Q104,105,106,107,108,109.
Recommended final inspection

Check for a burnt or deformed thermistor (attached to power cord plug & switch). Replace if defective. Make sure the toroidal transformer is tight and will not move easily by hand. Make sure the Phillips screws holding the main amp board (on the front of the faceplate) are tight. (Loose screws mean poor transistor heat sinking, possible premature failure). Make sure the correct line fuse is in place; RS-10: 3A, RS-12: 4A — (all ratings at 120v). Make sure the red, red/black output wires are still maintaining an airtight seal as they thread through the plastic amp cover.