Wednesday, June 29, 2016

How to diagonose - How to troubleshoot SMPS using STR G-6653 power switching IC

Troubleshooting procedure to Switched Mode Power Supply – using STR G-6653 IC as switching-out device
Fuse F601 (3.15Amps) blows out.
Check T601 transformer – for its winding short.  If the two of its windings will short each other, the fuse will blow out.
Check C602 [0.22/250V] capacitor for short.  Can check it with a multimeter set to measure Kohms range.  If shorted, replace it.
The PTC [R601] short.  Check it with multimeter.  If the fuse blows when the degaussing coil L601 is connected to circuit, and does not when it is disconnected, the fault is with the PTC itself. Replace it.
Short circuited [C601A & C601D – 0.0047] ceramic capacitor too can cause the fuse failure..Check both of them.  If found faulty, replace them. This is a common fault for fuse failure, especially when the set has hit by lightning. 
Shorted mains rectifier diodes [D601A~D601D], too can cause the fuse failure.  Even though any one among them is found faulty, replace all the four at one time.  It is a best practice in service.

Then comes the case of mains filter capacitor, C607 [220U/200V].  Short to this capacitor is very rare, might happen some times.  So check it too for any short circuit.
In the case of STR-G6653:  The most common fault happen to it is short circuited Source and Drain of its internal FET [Field Effect Transistor].  It is very easy to check.  Check the DC resistance between pin number (1 and 2) of the STR.  It will seem to be short circuited, when we connect the negative prob of the meter to pin-2 and the positive probe to pin-1; because, there is an internal diode fabricated inside this IC, which connects the Source and Drain of the internal FET.  The cathode of this diode is connected to pin-1 and the anode to pin-2.  So when we measure, the Dc resistance of (Pin 1 & 2), the DC resistance of this diode might misunderstand as a FET leak.  Reverse the polarity of the meter probs.  There SHOULD NOT be any short circuit [low ohms measurement].  If it shows low ohms measurement, the STR is damaged. Have to replace it.

There are some reasons for this STR to fail.  The first one is a sudden voltage spike at AC input voltage. The other one is loosely fitted STR to its metal heat sink.  If it is loosely fitted, the STR will overheat and will damage within minutes. Lightning strike.

If STR is found damaged [leaky], we have to check all the other components on board, related to STR control circuit.  Make sure that all of them are OK; before replacing the STR with a new one, other wise the chance of failure to the newly replace STR is about 90%.
Desolder out the damaged STR from the circuit, and check all the other components on board, related with it, one by one.  If the STR is shorted, check the two low value resistors [R604 & R603].  Both of them might have opened.  These two resistors are connected in parallel to ground and the pin-2 of the STR through a coil [L602].  Check this coil too for its continuity.  Check the high-speed switching diode [D605 IN4148] for short.  Replace it with a new one, even it shows no fault.  It is the best.  Special care should be given to [C608 0.001u/200v(2Kv)].  If this high voltage ceramic capacitor is opened or there is any loose solder terminal at any one of its 2 solder terminals, will cause the STR to burn out.  If this type of fault is there, and we have checked all the other components, and all of them are found OK; and when we apply AC power to the circuit; the new STR will blow out within microseconds.  We won’t get no time to measure any of the voltages that cause the damage of the STR.  Keep this in mind always, when you work with this kind of SMPS.  If you have a capacitance meter.  Measure the capacitance of this capacitor, and make sure it is good, and has not shorted or opened.  If this capacitor has a direct short circuit, inside, the fuse will blow out.  See how it is connected. Refer the circuit diagram.  One terminal is connected to main DC rail (+), through [L601] and the primary winding of [T603] and the other to Ground (-).  Now it is clear for the reason the fuse blows.

Check the transistor [Q601 – 2SC2482] and make sure that it is good.  Check the 15V Zener diode [ZD602] for any leak.  Desolder this diode out from circuit, and check it by multimeter (analogue type) set to KOhms range.  There shouldn’t be any reverse reading to this diode.
If all these checks are over, you can insert the new STR in place, screw it hard to its metal heat-sink (apply heat-sink compound, is highly recommended).  Never power ON the circuit now.  Disconnect the (B+) supply rail [the DC output of the SMPS] from the rest of the circuit.  Connect a 100W filament type bulb [do not use CFL or such type].  Re-check all the work done so far and make sure all are OK.  Check all the solder terminals at the SMPS section circuit for any dry solder. Re-solder any suspected, by applying a little more solder; without making any solder bridge short in between adjacent terminals.

Power ON the circuit.  If all are OK; the connected bulb will glow [at first it will show a bright light; and within 3 seconds or so, it will go dim]  Now measure the voltage across [C616].  It should snow around 110VDC.  Keep the circuit connected to AC, and watch the luminescence of the bulb.  There shouldn’t be any flicker or flicker effect.  Keep connected; and check its line to load regulation at about 20 minutes.  After that, you can connect  the rest of the circuit, after removing the bulb.

The SMPS refuses to start, even though all the components on board are OK. 
Sometimes, the power supply regulator won’t start, as soon as the main power switch is ON.  Sometimes, it will start after several attempts of power On/Off.  This is the fault to the start supply voltage to the SMPS.  Make sure that the contact of the main ON/Off switch is Ok.
Here with this circuit, you can note that there is a 3W resistor connected to the pin-4 of the STR, in series with main AC line.  The pin-4 is connected to the emitter of [Q601] too.  This is the start and retain voltage section.  What happens when we switch ON the set for the first time is, the pin-4 of the STR will get a low voltage through R607 from AC mains; and its control block inside will start up to work.  The STR will start to work, and the SMPS transformer too.  After the SMPS transformer start to work, it will generate a voltage, which is converted to DC by [D610 BA158], and that voltage is further regulated by Q601, and then supplied back to the pin-4 of the STR.  This voltage will take over the STR’s control block to work, till we switch OFF the set.  When we switch ON the set again, the same functions as described above will happen.  So, when this fault is noted [delayed start up], make sure that the [R607 – 39K3W] and its solder terminals too are OK, and R607 is not open.  Check the (R605 & R608 (2M2)) resistors too for open circuit.
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JWIN CRT TV – Circuit Diagram

Used semiconductors and ICs: LA8633xx (System control) – LA76814 (VIF Chroma Jungle) – 24C04 (Memory) – HEF4052 (Input Selector) – LA7840 (Vertical Output) – STR-G6653 (SMPS control) – LA4285 (Audio Output) – 2SD2499 (Horizontal scan output transistor) 
Circuit Diagram
STR-G6653 - SMPS circuit diagram
Click on the schematics to magnify

NAD DVD video player – T531B – T531C – T531AH – SMPS circuit diagrams

NAD T531B – T531C – T531AH – T512C – T512AH – DVD Video Player Power Supply Schematics
Click on the Schematics to Zoom in

NAD C521 compact disc player – schematic – mechanism exploded view

Used ICs: PCM1710U – LC78621ED – LC587206A - LA9240 – LA6541D – LB1641 – 5532
CHECKING THE BEAM EMISSION
  The laser beam of this unit is focused on the reflecting surface of the objective lens in the optical system block. Therefore, keep your eyes at least 12 inches (30 cm) away from the objective lens when the laser diode is ON. (Operation Check Method for Laser Diode and Focus Search Function.)
When the POWER switch is turned ON after the chucking plate is removed, observe the objective lens and confirm that the following operations are performed properly. (The optical system should be at the lead-in area position when it is checked at this time.)
(1) The laser should be at the innermost position after the chucking plate is removed.
(2) The diffused light of the laser beam can be seen when the POWER switch is turned ON.
(3) Vertical (up and down) movement of the objective lens (2 or 3 times) will take place.

  Laser diodes are extremely susceptible to damage from static electricity. Even if a static discharge does not ruin the diode, it can shorten its life or cause it to work improperly. When replacing the pick-up, use a conductive mat, a grounded soldering iron, and so on, to protect the laser diode from static damage.
Schematic diagram & PWB
CD11CA- Mechanism - exploded view

Monday, June 27, 2016

Yamaha AX396 Stereo Amplifier – Circuit diagram – Adjustments - Disassembly

Minimum RMS Output Power; 8Ω, 20Hz to 20kHz, 0.019% THD: 60W+60W
Maximum Output Power (EIAJ): 1kHz, 10% THD: 6Ω 110W
Dynamic Power (IHF): 8/6/4/2Ω: 100/120/140/150W
DIN Standard Output Power: 4Ω, 1kHz, 0.7% THD: 95W
IEC Output Power: 8Ω, 1kHz, 0.019% THD: 75W
Weight: 8.7 kg (19lbs 3oz)
Remote control model number: RAX9 V499920
Do not change the IMPEDANCE SELECTOR switch setting at the back of this set, while the power to this unit is on, otherwise this unit may be damaged.
Disassembly
(Remove parts in the order as numbered.)
1. Removal of Top Cover
Remove 4 screws (1) and 4 screws (2) in Fig.
2. Removal of Front Panel
a. Remove 6 screws (3) in Fig.
3. Checking and Parts Replacement of MAIN P.C.B. (1)
a. Disconnect the power cord from the AC outlet.
b. Remove 3 screws (4) attaching the Speaker terminal and Impedance Selector in Fig.
c. Remove 2 screws (5) and remove 1 plastic rivet (6) in Fig. then remove the Sub Chassis.
d. Remove 4 screws (7) in Fig. then remove the MAIN P.C.B. (1) with Heat Sink and Chassis.
Adjustments: Confirmation of Idling Current
> Right after Power is switched ON, confirm the voltages measures at R553 (L ch) and R561 (R ch) are between 0.1mV to 10mV.
> If it exceeds 10mV, open (cut off) R552 (L ch), R560 (R ch) and reconfirm the voltage.
PWB and Schematic
Click on the pictures to magnify

Yamaha AX496 Stereo Amplifier – Circuit Diagram – Adjustments - Disassembly

Minimum RMS Output Power
8Ω, 20Hz to 20kHz, 0.019% THD:  85W+85W
Maximum Output Power (EIAJ)
1kHz, 10% THD: 8Ω/6Ω 130W / 150W
Dynamic Power (IHF)
8/6/4/2Ω: 30/150/185/220W
DIN Standard Output Power
4Ω, 1kHz, 0.7% THD: 120W
IEC Output Power
8Ω, 1kHz, 0.019% THD: 100W
Weight
AX-496 9.5 kg (21lbs)
Remote control model number: RAX9 V499920
Do not change the IMPEDANCE SELECTOR switch setting at the back of this set, while the power to this unit is on, otherwise this unit may be damaged.
Disassembly
(Remove parts in the order as numbered.)
1. Removal of Top Cover
Remove 4 screws (1) and 4 screws (2) in Fig.
2. Removal of Front Panel
a. Remove 6 screws (3) in Fig.
3. Checking and Parts Replacement of MAIN P.C.B. (1)
a. Disconnect the power cord from the AC outlet.
b. Remove 3 screws (4) attaching the Speaker terminal and Impedance Selector in Fig. 
c. Remove 2 screws (5) and remove 1 plastic rivet (6) in Fig. then remove the Sub Chassis.
d. Remove 4 screws (7) in Fig. then remove the MAIN P.C.B. (1) with Heat Sink and Chassis.
Adjustments: Confirmation of Idling Current
• Right after Power is switched ON, confirm the voltages measures at R553 (L ch) and R561 (R ch) are between 0.1mV to 10mV.
• If it exceeds 10mV, open (cut off) R552 (L ch), R560 (R ch) and reconfirm the voltage.
PWB main - foil side
Schematic
Click on the pictures to zoom in

Sony FDL 390BE – Color Watchman – disassembly – Circuit Diagram

Used ICs: M52003AFP – NJM20730 – NJM2904 – TA7370 – TA8805F – AN5707NS – CX20159 
Power supply voltage is +9V DC.
Voltage adjustment
Connect a digital multitester between TP605 (+4.8V) and TP602 (Gnd) on the main board and then adjust RV601, so that the reading of the votage is +4.5V +/-0.05V.
Connect the multitester between TP606 (-8V) and TP602(Gnd), and then adjust RV602 so that the reading of the voltage is +4.2 +/- 0.05V.
Connect the digital multimeter between TP607 (+4.2V) and TP602 (Gnd), and then adjust RV603, so that the reading of voltage is +4.2 +/- 0.05V.
Schematic (Tuner & Main board)
Disassemble procedure
Click on the pictures to magnify

Saturday, June 25, 2016

LG 42 inch Plasma TV - faults - no raster - discharge - bars or lines

  There are several positive characteristics presented by a plasma TV, such as:
Possibility to build screens with large visual areas, and the most popular size today is 42-inch, reaching more than 100 inches, LG in Korea has the 102-inch model. In Brazil podese find purchase MW71PY10 model of 71 inches. Compared to other products such as CRT TV or LCD, plasma TV is leading to greater advantage when thinking about screen size. There is also television sets projection that can display screens of 60 inches, but lose brightness as the size increases screen, which does not occur with plasma televisions. The most common technology for projection televisions today are; kinescope, LCD, DLP and LCoS.
Very low thicknesses. Although not a unique characteristic of the plasma televisions, when combined with the characteristic of having large screens, plasma TV is extremely attractive, since it allows installation in walls such that an artistic picture. The space used by products today is highly valued, and compared to kinescope televisions plasma reaches easily have a tenth of the thickness of a conventional TV.
Weight proportionally smaller. Comparing the kinescope larger televisions with plasma which is lower persebe how a plasma TV is lighter than a conventional CRT. A 38-inch TV can reach have more than 100 kg, as a 42 inch plasma has around 40 kg
- Screen Uniformity. For plasma televisions there is no beam deflection, resulting in an image very more uniform without linearity problems.  A digital image consists of millions of points which are the picture elements known as pixels, while view this image we see in reality thousands of small luninosos points that together make the effect of image.
Does not suffer influence magnetic field. There around our planet a natural magnetic field, the same as guides compasses, which can cause minimum variations in kinescope TVs, the Earth's magnetic field interacts with the field of deflection yokes of conventional TVs causing small deformations, as well as any another magnetic field, be it from speakers or any other source, can cause major distortions or effects that cause spots on the kinescope screen. In plasma TVs each point individually lights.
NO RASTER
Check position SVC S / W
Checkpoint: Check the VSC Board position SVC S / W
Default: NO RASTER
Solution: Fix the position of S / W (Update S / W)
Unloading
Appears after-image as shadow.
It occurs in the old module.
Can solve with adjustment voltage VS. (+ / -  3~5V)
Defect: Discharge
If you cannot adjust VS voltage switch
YSUS Board.
Checkpoint: Check VSC Board
Defect : Discharge defect in any specific color
Change VSC Board.
Appears on the screen bars:  Module Control Board
Checkpoint: Check the version of Micon and Control Board
Default: With certain range appear the bars (OSD works normally)
Solution: Switch Module Control Board.
Module Control Board fault
Checkpoint: Check Control Board and connection cable VSX
Default: With certain range appear the bars (OSD works normally)
Solution: Switch Module Control Board.

Caixa MF 580 – USB – FM Schematic – TDA2030A – LM833 – CD4558 – L7575

Circuit diagram

Click on the schematics to zoom in

Friday, June 24, 2016

VSC board defects - Plasma TVs - No Power fault - Button does not work

NO POWER (button does not work)
1. LED is green but HAS RASTER
2. It does not work the CONTROL KEY
3. There appears OSD. There appears some color specific.
Distortion on the screen.  At this time, OSD functions Normal.
Not appear any specific color.
Checkpoint: Check VSC Board connection cable and settop box
Default: Does not appear any specific color
Solution: Replace VSC Board.

Image Warp
Checkpoint: Check boot VSC Board
Default: OSD functions normally but the image is distorted
Solution: Replace VSC Board.