REPAIRING AND NOT THROWING AWAY

REPAIRING AND NOT THROWING AWAY

Richtige Fernseher haben Röhren!

Richtige Fernseher haben Röhren!

In Brief: On this site you will find pictures and technical information about Service Modes, Circuit Diagrams, Firmware Update procedure, Disassemble procedure, Universal remote control set-up codes, Troubleshooting and more....

If you go into the profession, you will obtain or have access to a variety of tech tips databases HERE IT IS Master Electronics Repair !.

These are an excellent investment where the saying: 'time-is-money' rules. However, to learn, you need to develop a general troubleshooting approach - a logical, methodical, method of narrowing down the problem. A tech tip database might suggest: 'Replace C536' for a particular symptom. This is good advice for a specific problem on one model. However, what you really want to understand is why C536 was the cause and how to pinpoint the culprit in general even if you don't have a service manual or schematic and your tech tip database doesn't have an entry for your sick TV or VCR.

While schematics are nice, you won't always have them or be able to justify the purchase for a one-of repair. Therefore, in many cases, some reverse engineering will be necessary. The time will be well spent since even if you don't see another instance of the same model in your entire lifetime, you will have learned something in the process that can be applied to other equipment problems.
As always, when you get stuck, checking out a tech-tips database may quickly identify your problem and solution.In that case, you can greatly simplify your troubleshooting or at least confirm a diagnosis before ordering parts.

Happy repairing!
Today, the West is headed for the abyss. For the ultimate fate of our disposable society is for that society itself to be disposed of. And this will happen sooner, rather than later.

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..............The bitterness of poor quality is remembered long after the sweetness of todays funny gadgets low price has faded from memory........ . . . . . .....
Don't forget the past, the end of the world is upon us! Pretty soon it will all turn to dust!

©2010, 2011, 2012, 2013, 2014 Frank Sharp - You do not have permission to copy photos and words from this blog, and any content may be never used it for auctions or commercial purposes, however feel free to post anything you see here with a courtesy link back, btw a link to the original post here , is mandatory.
All posts are presented here for informative, historical and educative purposes as applicable within fair use. NOTHING HERE IS FOR SALE !

Monday, 4 February 2019

LG CM8450 TROUBLESHOOTING AND CIRCUIT DIAGRAM MINI HI-FI SYSTEM

LG CM8450 Troubleshooting and Circuit diagram Mini Hi-Fi System

Used ICs: PS9860, CS5346-CQZR, PCM1808, IRD2092 x 5 (Amp-IC), MLC3730S, M9812G, R5F100GEAFB, BU9546KV, AM5890, TPS54331D, 2RA20112ASP, STR2A153D - LG CM8450 (CM8450, CMS8450F/W) MINI HI-FI SYSTEM
Troubleshooting
NO POWER
If the unit doesn’t work by no power problem, repair the set according to the following guide.
FUSE/ BRIDGE DIODE/ THERMISTOR
Solution
Please check and replace F901, BD901, TH900, TH901 on SMPS board.
How to troubleshoot (Countermeasure)
1) Check if the fuse F901 is open or short-circuit.
2) Check if the bridge diode BD901 is short-circuit by over current with a digital multimeter.
3) Check if the NTC thermistor TH900~TH902 is normal or open.
NO AMP POWER
If the unit doesn’t work by no ±PVDD problem, repair the set according to the following guide.
FUSE/ FET
Solution
Please check and replace F911, Q905~Q906 on SMPS board.
 How to troubleshoot (Countermeasure)
1) Check if the fuse F911 is open or short-circuit.
2) Check the Drain-Source or Drain-Gate, Gate-Source Resistance of Q905~Q906 with a digital multimeter.
  If it is short condition, it’s destroyed. Replace it with a new one.  (Please replace 2 FET at the same time although several FET is OK).
SMPS circuit diagram [Click on the pictures to magnify]
NO BOOTING WHEN POWER ON THE SET
The set doesn’t work when presses the power button on the FRONT_CTRL board or the remote control.
How to troubleshoot (Countermeasure)
1) Check the 5.6 VA (CN106) and DVCC_3.3 V (IC505) in standby mode.
  If there is no 5.6 VA, check the SMPS and if doesn’t appear 3.3 V, check IC505.
2) Check 5.6 VA, +12 V, FL+, FL-, an +39 V when power on the set.
  If the set doesn’t work regardless of what the KEY2 changes high to low
while pressing the power button. X500 and X501 work normally but, if you cannot power on the set, replace the IC501 with a new one on the MAIN board.
VFD IS NOT DISPLAYED WHEN POWER ON THE SET
When power on the set, any icons or characters on VFD are not displayed.
How to troubleshoot (Countermeasure)
1) Check if 39 V, FL+ and FL- are output from SMPS to VFD via the MAIN board.
2) Check if the IC501 outputs VFD_RST, VFD_CLK, VFD_DO, and VFD_STB to the FRONT board.
3) Check if the VFD grid current amplifier circuit on the FRONT board.
Check the drive signal to the transistor’s base.
  If the control signals from VFD (DGND_2, VH, VDD) isn’t output, replace VFD with a new one.
AUDIO OUTPUT IS SMALL OR NO AUDIO OUTPUT
Audio signal output is small or not. when you power on the Middle Power Mini System
How to troubleshoot (Countermeasure)
1) Please check if this system is on bass blast mode.
  C, RL and RR make sound only on bass blast mode.
2) Check the IC700~IC705 on your eyes.
3) Check the audio signal output check (pin13 of IC700~IC705).  First, Check the PWM Data input (pin3 of IC700~IC705)
4) If the audio signal output has no output, try to change IC which has no output.
5) Lastly, check Speaker Terminal (TM700).
NO POWER ON (STANDBY LED IS BLINKING)
It doesn’t turn on, and blinks standby LED(Red).
AMP FETs
Solution
Replace AMP FET on MAIN board.
How to troubleshoot (Countermeasure)
1) This symptom occurs, when DC protection is detected. Main reasons are like below.
- When some of AMP FETs dead.
SPEAKER NO AUDIO
Speaker No Audio
AMP IC (IC700~IC705)
Solution
Replace IC700~IC705 on MAIN board.
How to troubleshoot (Countermeasure)
1) Check supply voltage of AMP(CN110) & PWM signal  Normal supply voltage and signal > Check AMP IC.  Poor supply voltage > Check SMPS Assy.
Poor signal Æ Check PWM IC.
2) Check CSD of FET driver IC (IRS2092 : EAN60778301).
CSD has about 5 V on normal state.
When AMP has problem, CSD is LOW state or keep change LOW to HIGH.
NO BOOTING IN CD/USB FUNCTION - 1
After you turn on power key and displayed message in the following order (HELLO > VOL XX > CD or USB) on VFD, it will not display other message on VFD, and it will not boot-up normally.
NO VCC33, VCC12
Solution
Please check and replace IC505, IC500 on MAIN board.
How to troubleshoot (Countermeasure)
1) Check Voltage of IC505 pin3 on MAIN board.
  If IC505 pin3(about 4.9 V) & D500 Input 5.6 VA doesn’t come out, check 5.6 VA from SMPS board.
2) If IC505 pin3(about 4.9 V) is normal, check the PWR_CTRL(IC505 pin2) is high (about 3.3 V)
  If PWR_CTRL isn’t high, check pin B2 of IC501 & R524, R522
3) If PWR_CTRL is high, check R524 and if there’s no defective component then replace IC505.
4) If 3.3 V(VCC33) is normal, check 1.2 V output(pin2) voltage of IC500
  If 1.2 V of IC500 pin2 doesn’t come out, then replace IC500.
NO BOOTING IN CD/USB FUNCTION - 2
After you turn on power key and displayed message in the following order (HELLO > VOL XX > CD or USB) on VFD, it will not display other message on VFD, and it will not boot-up normally.
CRYSTAL (X500)
Solution
Replace X500 on MAIN board.
How to troubleshoot (Countermeasure)
1) If 3.3 V & 1.2 V is normal, Check the CHIP_RESET of IC501 pin T12 on MAIN board.
 If CHIP_RESET isn’t high, Check MICOM(IC101) pin40.
2) If CHIP_RESET is high, Check the soldering status of 24 MHz crystal (X500).
3) If the crystal (X500) doesn’t oscillate, Check R508, R509, C502, C503 around crystal (X500).
 If there’s no defective component, then replace X500.
NO BOOTING IN CD/USB FUNCTION - 3
After you turn on power key and displayed message in the following order (HELLO > VOL XX > CD or USB) on VFD, it will not display other message on VFD, and it will not boot-up normally.
SERIAL FLASH (IC503)
Solution
Please check and replace IC503 on MAIN board.
How to troubleshoot (Countermeasure)
1) If the crystal(X500) does oscillate, Check Serial Flash(IC503) on MAIN board.
  Check 8pin(VCC), 6pin(CLK), 1pin(CS), 2pin(DO), 5pin(DI) of below waveform.
2) If pin8, 6, 1, 2, 5 doesn’t come out, Check damping resistor(R564, R563, R535, R536, R534) of IC503.
  If damping resistor of IC503 is OK, then replace IC503. (it need to download program)
3) After change IC503, if It is still not below waveform, Check IC501(DSP IC).
NO BOOTING IN CD/USB FUNCTION - 4
After you turn on power key and displayed message in the following order (HELLO > VOL XX > CD or USB) on VFD, it will not display other message on VFD, and it will not boot-up normally.
SDRAM (IC502)
Solution
Please check and replace IC502 on MAIN board.
How to troubleshoot (Countermeasure)
1) Check below waveform & soldering status of SDRAM (IC502) on MAIN board.
 If pin17(#CAS), pin18(#RAS), pin19(#CS), pin38(CLK), pin29(address), pin2(DQ) doesn’t come out,
Check damping resistor (R568, R570, R544, R547).
2) If resistor is OK, then replace IC502(SDRAM).
3) After change IC502, if It is still not below waveform, Check IC501 (DSP IC).
NO BOOTING IN CD/USB FUNCTION - 5
After you turn on power key and displayed message in the following order (HELLO > VOL XX > CD or USB) on VFD, it will not display other message on VFD, and it will not boot-up normally.
DSP (IC501)
Solution
Please check and replace IC501 on MAIN board.
How to troubleshoot (Countermeasure)
1)After check them by Previous pages about NO Booting, if the set is still no booting,
  Check soldering status of IC501.
2) If below bootstrap waveform doesn’t come out, then replace IC501(DSP IC).
Servo schematic
ADC shematic
CD-DSP schematic
NO OPERATION OF MD - 1
When no sound output in the CD function, you can not listen to music reading data from a CD disc if the servo motors in MD don’t work. This step is for checking the spindle motor among them.
SPINDLE MOTOR
Solution
Replace IC401 or IC400 on MAIN board.
How to troubleshoot (Countermeasure)
1) Check the SPDO signal from pin16 of IC401.
 If no signal, check 3.3 V (RF) and X400.
2) Check the SPIN- & SPIN+ from IC400 to CN401 for driving SPINDLE motor. It is about 3.6 Vp-p.
 If no signal, check +7 V for IC400.
3) Check if the FFC cable is solidly connected between CN401 and MD.
4) Check the MD.
 If the spindle motor is short-circuit or has any trouble, it cannot rotate CD discs.
Please check the function after changing another MD.
NO OPERATION OF MD - 2
When no sound output in the CD function, you cannot listen to music reading data from a CD disc if the servo motors in MD don’t work. This step is for checking the sled motor among them.
SLED MOTOR
Solution
Replace IC401 or IC400 on MAIN board.
How to troubleshoot (Countermeasure)
1) Check the SLDO signal from pin23 of IC401.
  If no signal, check 3.3 V (RF) and X400.
2) Check the SLED+ & SLED- from IC400 to CN401 for driving SPINDLE motor. It is about 2.9 Vp-p.
  If no signal, check +1.8 V and +5 V for IC400.
3) Check if the FFC cable is solidly connected between CN401 and MD.
4) Check the MD.
  If the sled motor is sort-circuit or has any trouble, it cannot move the pickup module.
Please check the function after changing another MD.
NO OPERATION OF MD - 3
When no sound output in the CD function, you cannot listen to music reading data from a CD disc if the servo motors in MD don’t work. This step is for checking the tray open/close motor among them.
TRAY OPEN/ CLOSE MOTOR
Solution
Replace IC401 or IC400 on MAIN board.
How to troubleshoot (Countermeasure)
1) Check MOT_OPEN & MOT_CLOSE signals from pin K4 & L4 of IC501 to IC400.
  If no signal, check +1.8 V & + 5 V to IC400.
2) Check LOAD ± from IC400 to CN401 for driving the tray open/ close motor. It is about 3.85 Vp-p.
  If no signal, check +5 V to IC401. If it has any trouble, replace it with a new one.
3) Check if the FFC cable is solidly connected between CN401 and MD.
4) Check the MD.
  If the tray motor is short-circuit or has any trouble, it can not open or close the tray.
Please check the function after changing another MD.
NO OPERATION OF MD - 4
When no sound output in the CD function, you can not listen to music reading data from a CD disc if the pickup module in MD doesn’t work. This step is for checking the laser tracking actuator.
LASER TRACKING ACTUATOR
Solution
Replace IC401 or IC400 on MAIN board.
How to troubleshoot (Countermeasure)
The tracking actuator makes the laser beam be positioned in the center of a track on CD disc.
1) Check the TRD signal from pin14 of IC401.
  If no signal, check 3.3 V (RF) and X400.
2) Check TR- & TR+ from IC400 to CN400 for driving the tracking actuator.
  If no signal, check +1.8 V and +5 V for IC400.
3) Check if the FFC cable is solidly connected between CN400 and MD.
4) Check the MD.
  If the pickup module has any trouble, it can not move the laser beam on the left or right side.
Please check the function after changing another MD.
NO OPERATION OF MD - 5
When no sound output in the CD function, you can not listen to music reading data from a CD disc if the pickup module in MD doesn’t work. This step is for checking the laser focusing actuator.
LASER FOCUSING ACTUATOR
Solution
Replace IC401 or IC400 on MAIN board.
How to troubleshoot (Countermeasure)
The focusing actuator makes the laser beam keep a regular interval with the surface of a CD disc.
1) Check the FDO signal from pin13 of IC401.
 If no signal, check 3.3 V (RF) and X400.
2) Check F- & F+ from IC400 to CN400 for driving the focusing actuator.
 If no signal, check +1.8 V and +5 V for IC400.
3) Check if the FFC cable is solidly connected between CN400 and MD.
4) Check the MD.
 If the pickup module has any trouble, it can not move the laser beam on the top or bottom side.
Please check the function after changing another MD
Power amplifier schematic
NO SOUND - 1
There is no sound output in the USB function, repair the set according to the following guide.
USB FUNCTION
Solution
Replace IC501 on MAIN board, IC312 on FRONT board.
How to troubleshoot (Countermeasure)
1) Check +5 VU to FRONT board.
 if +5.6 VA to pin2 of IC312(LDO) doesn’t come out, check pin4 & 5 of CN314.
 if +5.6 VA is normal & +5 VU of IC312 pin3 doesn’t come out, then replace IC312.
2) Check “Digital audio AMP block”.
NO SOUND - 2
There is no sound output in the AUX function, repair the set according to the following guide.
AUX FUNCTION
Solution
Replace IC201 on MAIN board.
How to troubleshoot (Countermeasure)
1) Check AUX_L/R signals to IC201 (pin23, 24).
2) Check if MCS_BCK, MCS_LRCK, & MCS_MCLK are entered from IC501 to IC201.
3) Check if ADC/MIC_DATA is entered from IC201 to IC501.
 If no signal, check +5 V & +3.3 V(ADC) for IC201. If is NG, replace it a new one.
4) Check the following I2S signal flow from IC501 to IC202.
 If there is any trouble, check the power for each IC. The power is normal but, if the signal waveform to
the IC is distorted or no signal, replace it with a new one.
5) Check if the digital audio AMP block is okay.
 If AMP is damaged, replace it with a new one.
NO SOUND - 3
There is no sound output in the PORT. IN function, repair the set according to the following guide.
PORT. IN FUNCTION
Solution
Replace IC201 on MAIN board.
How to troubleshoot (Countermeasure)
1) Check PT_L/R signal from FRONT board to MAIN board.
2) Check if PT_LR is entered pin25 & 27 of CN605 ð pin25 & 27 of CN315.
3) Check PT_L/R signals to IC201(pin9, 10).
4) Check if ADC_BCK, ADC_LRCK & DAC_MCLK are entered from IC501 to IC201.
5) Check if ADC_DATA is entered from IC201 to IC501.
  If no signal, check +5 V & +3.3 V(ADC) for IC201. If is NG, replace it a new one.
6) Check the following I2S signal flow from IC501 to IC202.
  If there is any trouble, check the power for each IC. The power is normal but, if the signal waveform to the IC is distorted or no signal, replace it with a new one.
7) Check if the digital audio AMP block is okay.
  If AMP is damaged, replace it with a new one.
NO SOUND - 4
There is no sound output in the TUNER function, repair the set according to the following guide.
TUNER FUNCTION
Solution
Replace IC201, TU500 on MAIN board.
How to troubleshoot (Countermeasure)
1) Check if TUNER_L/R is entered from pin1 & 3 of TU500 to IC201(pin26, 27).
  If no signals, Check +3.3 V for Tuner power.
  Check if the Tuner control signals (CLK, DAT, CE, RST, GPO2) are entered from IC501 to TU500.
If it doesn’t work, replace TUNER with a new one.
2) Check if ADC_BCK, ADC_LRCK & DAC_MCLK are entered from IC501 to IC201.
3) Check if ADC_DATA is entered from IC201 to IC501.
  If no signal, check +5 V & +3.3 V (ADC) for IC201. If is NG, replace it a new one.
4) Check the following I2S audio signal flow from IC501 to IC202.
  If there is any trouble, check the power for each IC. The power is normal but, if the signal waveform to the IC is distorted or no signal, replace it with a new one.
5) Check if the digital audio AMP block is okay.
  If AMP is damaged, replace it with a new one.
NO SOUND - 5
There is no sound output in the MIC IN function, repair the set according to the following guide.
MIC IN FUNCTION
Solution
Replace IC200, IC206 on MAIN board.
How to troubleshoot (Countermeasure)
1) Check MIC_SIG signal to pin33 of CN605.
  If no signal, Check the signal to pin33 of CN315 on the FRONT board.
Check if the signal is entered from pin6 of CN605 to MAIN board.
2) Check if MIC_SIG is entered from pin33 of CN605 to pin3 to IC200 (MIC AMP).
3) Check if the amplified signal comes out from pin4 of IC200.
  If no signal output, check +12 V for IC200, replace IC200 with a new one if it has a problem.
4) Check if MCS_BCK, MCS_MLCK & MCS_LRCK is entered from IC501 to IC206.
Check if MIC_DATA_IN is entered from pin9 of IC206 to pin T1of IC501.
  If no signal, check +5 V & +3.3 V for IC206. If it is abnormal, change replace it a new one.
5) Check the following I2S signal flow from IC206 to IC501.
  If there is any trouble, check the power for each IC. If the signals are abnormal, replace it a new one.
6) Check if the digital audio AMP block is okay.
  If AMP is damaged, replace it with a new one.
NO SOUND - 6
There is no sound output in the Bluetooth function, repair the set according to the following guide.
BLUETOOTH FUNCTION
Solution
Replace IC501 on the MAIN board or B/T module on the Front Panel.
How to troubleshoot (Countermeasure)
1) Check BT_RX, BT_TX signal to pin4, 6 of CN504.
 If no signal, Check the signal to pin4, 6 and pin10 (+3.3 V) of on the Bluetooth module and cable
connection state.
 If there are no signal out from module, replace new module.
2) Check if BT_RX/TX is entered from pin4, 6 of CN504 to pin K1, L1 to IC501 (DSP).
3) Check the following I2S signal flow from IC501 to IC600.
 If there is any trouble, check the power for each IC. If the signals are abnormal, replace it a new one.
4) Check if the digital audio AMP block is okay.
 If AMP is damaged, replace it with a new one
Posted By: FRANK at 01:58
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