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........ . . . . . .....
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Monday 4 March 2019

HOW TO DIAGNOSE - HOW TO TROUBLESHOOT SMPS USING STR G-6653 POWER SWITCHING IC


How to diagnose - 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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