Daewoo TV DTQ-2072 repeated blowing of fuse

Where can the problem be if the main fuse in the TV power supply blows fuse repeatedly?
This was a problem I have encountered with a Daewoo TV model# DTQ-2072. The fuse blows even when the IC regulator  STR-59041 has been replaced. To isolate the cause of the problem, I replaced the fuse again and disconnenected the PTC thermistor on board location RH02.
I plugged the set to AC outlet and powered up the set from standby. The picture and sound came up but the picture has color smears(dynamic misconvergence) on the sides of the screen - a result of disconnecting the thermistor which passes momentary current to the degaussing coil.
An ohmmeter check on the thermistor shows that it has developed a higher resistance. Opening the plastic case of the PTC thermistor revealed that the thermistor discs are burnt.
Replacing the PTC thermistor eliminated the  color stains on the picture and solved the problem of  blowing of fuse.

Sony TV KV-21GMR1 power problem:SE115N error amp defect

Sony TV model# KV-21GMR1 is a dead set: no LED standby indicator light, +115V supply to horizontal output transistor measured only 27V and is pulsating.
The SMPS regulator IC STR-S6707 was replaced but still the +115v supply line is dropped.
Even when the horizontal output transistor is disconnected from the circuit the +115V supply will not increase.
An ohmmeter check on the SE115N error amplifier shows that it is internally open circuited.
Power was restored to the set when the SE115N was replaced.

Philips CTV 29PT2252/56A (L01.1A chassis)problem:intermittent pincushion distortion

This Philips TV model# 29PT2252/56A exhibited intermittent increase in picture width with pincushion distortion and blanking of picture.
A visual inspection of the printed circuit board reveals solder crack on pin 1 of pincushion transformer on board location 5465/5464/5463.
Resoldering of the cold solder on the pincushion transformer solved the problem of  intermittent picture width and pincushion distortion.

Sony TV KV-25JXR20 reduced horizontal width problem

The owner of a Sony TV with model number KV-25JXR20 complained of the reduced horizontal width of the picture of his TV. He also observed "blinking" of the picture which must be his description of intermittent blanking of the picture.
During my initial observation of the problem I also noticed that the vertical size of the picture is in overscan - or stretched - resulting to vertical mislinearity and the presence of red, blue and green blanking lines at the top edge of the picture.
I suspected capacitors with changed values in the vertical deflection circuit and the horizontal deflection or pin correction circuits. Since the TV is already in the vicinity of being ten years of age, I also considered the possibility of dry solder joints.
Since there was no obvious bulging capacitors in my initial inspection of the main PCB I proceeded to resolder the deflection circuits and some parts of the chopper transformer, filter capacitors and rectifier diodes in the secondary circuit of the power supply.
After the soldering exercise, I powered-up the TV again to check if the problem was solved. I was not much surprised to see that the problem still persists since there was not really any obvious cracked or dried up solder joints on the TV's circuit board.
Doing another visual inspection on the component side of the PCB, I noticed the slight bulge on the top of a filter capacitor that was sitting beside the chopper transformer. I desoldered the capacitor and found out that it is a 100uF/160V electrolytic capacitor on PCB location number C609. A look under the capacitor revealed signs of electrolyte leakage. With the capacitor leads still hot from contact with the soldering iron I can still see the electrolyte boiling out of one of the capacitor leads.
By replacing this capacitor only, I was able to solved both the problem with reduced horizontal width and vertical mislinearity.

JVC TV AV-J21MX: No power problem

This TV that came in for repair was found to have a Horizontal Output Transistor D1878 (on board location Q522) with a short between the collector to emitter. When the defective transistor was pulled out of circuit there was still a short measured from the B+ line to ground. The deflection yoke was unplugged from the TV's main board but still the short was present.


Tracing back towards the power supply it was found out that a shorted RU3A diode on board location D921 is shorting the B+ line to ground.

Replacing the transistor D1878 and diode RU3A restored power and normal operation to the set.

Philips Projection TV dark horizontal lines on picture

A Philips 43PP7445/69 Projection TV came in for repair with complaints of black horizontal lines on the picture. At first it seems that an interference in the video circuits is causing the problem. But when I entered the convergence alignment mode the problem showed itself as horizontal jittering which can be seen in the vertical lines of the convergence alignment cross.

By swapping boards the problem was isolated to the ACS Panel which controls the convergence alignments.

Philips FW-399V: Tape stops on rewind and fast forward

A Philips Mini-Component with 3-VCD Rotary Changer and tape deck has symptoms of tape automatically stopping within 3 seconds in the rewind and fast forward mode. Tape playback function, though, is normal.

I have replaced the rubber belts on both tape decks as part of the routine service procedures but tape deck still automatically stops and can't finish rewind or fast forward action.

I noticed the optical encoder discs located behind the tape deck to be dusty and tarnished so I cleaned it using cotton swab.



Cleaning the optical disc encoder finally solved the problem of tape stopping on rewind and fast forward mode.

How to fix an Epson Printer C45 stripping gears noise problem

Most problems that occur in an electromechanical equipment is caused by mechanical rather than electrical defects. And most mechanical defects reveals itself by performing a visual inspection of the mechanical parts. Being able to open the equipment and looking at the parts under the cover is almost halfway to solving the problem.

Take the case of a problem with an Epson C45 printer which I have encountered just recently. The ink cartridge carrier will move to the left side slowly then back to the right side again. As the ink cartridge carrier nears its park position a stripping gear noise is heard and the cartridge carrier appears blocked in completing its travel.

From here on there is no other way to go but to open the unit and inspect what the problem is from inside.

To open the printer I removed one screw located between the label and AC plug terminal at the back of the machine.



To remove the top cover there are four locks that need to be unhooked using a small flat screw driver.

Two of the locks can be found at the back on the lower left and right side of the unit. These locks can be unhooked by pushing through the small rectangular holes.

The other two locks are located at the front and can be accessed through the small rectangular holes located at the bottom corners of the base cabinet. I inserted the flat screwdriver blade through the holes and pried the hooks loose.

After the four locks have been unhooked...




















... the top cover can now be removed.

Once inside the machine I noticed the ink cartridge carrier pressing against a white lever which must be the object preventing it to reach park position.


I pushed the ink cartridge carrier a little bit back...



... then pushed the lever towards the cartridge...



and it snapped into place, no need to use force.
















I plugged the printer to AC outlet, pressed the power button, tested the unit and found it to be working just fine.

Sony TV KV-1982NG Power Supply Problem

Symptom: Dead set
Cure: Replace R602(220K ohm/0.5W)
Repair details:
No voltages measured at collector terminal of horizontal output transistor.
Voltage supply was measured across power supply filter capacitor terminals. Traced the PCB foil from the B+ terminal of the positive side of power supply filter capacitor to 220K ohm resistor(R602). B+ is measured on one side of the resistor R602 but no voltage measured on its other terminal. By using ohmmeter test it is found out that R602 is open-circuited.

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Philips TV L01.2 chassis problem: criss-crossing white lines on a dark raster

TV troubleshooting is about reading the lines on the screen. And in an electronic repairer's work troubles appearing as strange lines on the screen or picture of the TV crop up from time to time. These types of trouble in a CRT TV are most often cause by a problem affecting the scanning or deflection circuits. An example of these TV troubles manifesting as weird lines on the picture was tackled in one of my previous post where a capacitor in the vertical output circuit has decreased in capacitance and caused black lines to flicker across the picture.

The other day as I was flipping through a notebook that I keep where I jot down details of troubleshooting work that I have done I came across a record of a weird lines on the picture problem. Initially the symptom is 'no picture, dark raster'. Increasing the G2 control on the flyback transformer revealed strange lines that break white and zigzag across a blank raster.
I was also able to keep a camera shot of the symptom which you can see below.



The lines tell of trouble that lies in the vertical scanning circuit. The lines are symptomatic of excessive vertical scan distortion and fold-over. The TV chassis contains a TDA8172 vertical output IC which does not feel warm when you touch it. This would mean it is not overdriven or overloaded. Voltage measurement on the vertical output IC indicate normal supply voltages. What is obviously abnormal is the voltage on the output pin 5 which measures +5V instead of 0V. Replacing the IC did not provide the cure to the problem.

I decided to scope the input signals to the TDA8172 vertical output IC and discovered that the Vdrive+ signal on pin 17 of the UOC TDA9580 was generating a rectangular wave pulse instead of a sawtooth pulse. Both the Vdrive+ and Vdrive- The UOC was diagnosed to be defective since the sawtooth pulse is supposed to be generated from inside the UOC. A normal picture was restored to the set when the UOC was replaced.

Vertical deflection problem: horizontal gaps on picture

Coming at the tail-end of 2008 a day before New Year's Eve, a repair technician came to me for help in the repair of a 21-inch TV.
There was a problem in the picture of the TV which looks like black horizontal stripes and gaps on the screen. The picture below would describe to you more about the symptom.


















And here's another photo:



According to the technician, he has already replaced the TDA8172 vertical output IC. Unfortunately, the trouble still persisted.
The vertical output IC is obviously running hot as you can get singed just by touching its heat-sink for just a few seconds.

Based on the symptoms there appears to be non-linearity in the vertical scanning as indicated by the gaps in the picture. A slight fold-over in the top edge of the picture can also be noticed.
Since the vertical output IC has already been replaced, I set my sights on the minor components in the vertical deflection circuit.

According to the technician he has already tested the resistors and capacitors located around the vertical output IC using the ohmmeter of an analog multimeter and found no open or changed value resistors. He tested the capacitors' charging and discharging action also using the analog ohmmeter.
Digging in to the guts of the TV, I set my sights on the capacitors first as they are known to be the passive components with the highest failure rate - second only to ICs and transistors. Capacitors are better tested with a capacitance meter, not to mention the ESR meter, I skipped testing the capacitors with the ohmmeter. Testing the capacitors around the vertical output with a capacitance meter I found one mylar capacitor whose measured capacitance was way off its rated value. As indicated on its package its value should be 220nF/63V. However, this capacitor only registered 3.2nF on my capacitance meter. Apparently, this capacitor has decreased in capacitance to, approximately, less than 2 percent of its rated value.
Getting another capacitor with similar indicated value from my parts bin, I tested it on the capacitance meter to verify the rating before using it to replace the original capacitor which has decreased in capacitance.
After installing the new capacitor, the TV set was again turned on. Now we see a clean picture - the black gaps and lines have completely disappeared.
So now we have identified the cause of the problem to be the 220nF/63V mylar capacitor located a fraction of an inch to the right of the TDA8172 IC.
Tracing the connections on the printed circuit board and a review of the TDA8172 datasheet, it was found that the capacitor was connected to the output pin of the vertical output IC through a 1.5 ohms resistor. The capacitor's other pin is connected to ground pin of the vertical output IC.

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TV deflection coil defect

Modern TVs are designed to shutdown when problems are present either in the power supply or its loads to prevent the set from incurring further damage.

This protection feature was exhibited in a 14-inch TV which was brought in the shop for repair.

The set appears to power-up but will shutdown even before a raster is visible on the screen. A soft hissing sound can also be heard during the one or two seconds before shutdown.

The B+ supply voltage going to the horizontal output transistor's collector was measured but drops in that short moment before shutdown.

The scan-derived supplies going to the CRT panel such as the G2 and video output circuit supply voltages are both dropped.

Because of the hissing noise heard before shutdown the flyback transformer was suspected to have a high voltage leak that may be causing arcing noise. But a few tries to power-up the set reveals the source of the noise to be somewhere around the neck of the CRT. However, arcing was not visible inside the CRT neck. So the next possible source of HV arcing or leak is the deflection coil.

Next step was to unplug the deflection coil connector. When the set was powered on B+ voltage did not drop and there is a palpable rush of high voltage to the CRT. Its filament was also noticed to be lighted. This meant that a short or leak was removed when the yoke was unplugged.

When the yoke was disassembled the source of arcing was uncovered. Looking inside the yoke reveals burnt marks in the inner windings of the deflection coils.

When a deflection yoke burns it is usually at the outer edges of the windings or in the area in between windings as shown in the photo below. Notice the blackened edges of the winding on the left. In this case, the coil also reeks of a bitter smell.

Now that the cause of the trouble has been identified the only problem now is where to find a replacement part for the burnt deflection coil.