PICTURE TUBE BASED TELEIVISIONS _ ALL TYPES _ ANY MODELS

Fault:- Color distortion.  Intermittent or permanent.

A small hit on the backside of the TV cabin will make it right, at least for a moment. On some others can’t. With some sets, color combination will come right after a few minutes after switch ON.  On some others, at first the color will be all right, but after some time, all color balance will be out and will show irregular color combination.

  Eventhough, there is many reasons for irregular color reproduction with CRT based televisions, the most common fault will be with loose soldering points at the Video Output Section.  In most of the TVs, the video output section will be at its picture tube baseboard itself.  Older TVs of Mitsubishi, have this section is assembled at main board itself, and only wires are connected to picture tube baseboard.

  Take the first case.  (A small hit on the backside of the cabinet, makes color and picture right, at least for a moment.

  The fault is with loose soldering points on the video output section, assembled on the base card of the picture tube.  As you know, proper mixing of the three primary colors, Red, Green and Blue, does all the color combination.

  If any one among the primary color misses, you will get a picture with something strange to describe. 

Take the first case.  With a small hit on the back or side of the TV makes it right even for one moment or so.

The fault is with some loose soldering points itself.  But, must check and detect the exact point of fault. As I said earlier, the fault is with video output stage itself, which is venerable to get loose soldering points.  Most of the components at the video output stage, whether it is assembled on main board, or at the picture tube baseboard, should be checked for loose soldering points. 

  You will get the exact fault point, by a close look at this board itself.  Look for any cracked soldering points.  You may have to use a magnifying glass to get these solder cracks, as some of them will be microscopic.  Just do, what we do in service field if the fault detected is with loose soldering.  Just resolder all the soldering points on the base card board, including picture tube base card connections, by applying al little more solder to each solder points, without making any solder short in between adjacent solder terminals.  If the fault was due to loose contact with this video output card, it will be all right by now. You can solder all these solder terminals with base card plugged in.

  If the fault is not with this base card, you have to go further to chroma section circuits of the TV, and you must have knowledge and proper testing tools, schematic diagram of your TV set. Must have concentration and patience.  Without patience, you can’t do any work in electronics repair.

SONY WEGA KV-TG21L70 _ KV-TG21M80 _ KV-TG21P52.

Tuning does not lock up. 

When connected to on-air or RF cable services, when you tune in the TV, the channels does not lock up  and goes non-stop tuning process. 

No tuning lock. But tuning process is on the way.

     This fault is due to its memory IC.  The memory IC used with this set is (IC003) [(M24C08-BN6(A)] . Please note the number of this IC.  Even thouth it is very small in size, and very cheap to buy, function of this IC in circuit is great. When replacing it, be very cautious about the number. Must replace it with same number, otherwise the TV won’t even switch ON.  When replacing this IC, replace the reset IC (IC002) [MM1319AFBE] too.  Both of them are ‘8’ solder terminal DIL type ICs.

     As far as tuning lock is concerned, these are the components to be suspected and replaced. All the other [including mains system control IC, tuner etc:- are working well, otherwise, you won’t get any picture at the screen for a glimpse at all.

 

     Please note, without a stable picture, there will be no sound with this set, as sound is muted till steady picture gets out.

SONY WEGA SERIES KV-TG21L70 _ KV-TG21M80 _ KV-TG21P52

Set switches ON but switches OFF by itself, standby light blinks two times.

Over current protection circuit detects an overload on B+135VDC, supply line to LOT and Horizontal oscillator drive section, and gives the indication by two continuous blinks.

     Desolder and disconnect one end of resistor R502 (1.2 Ohms 2W), which supplies the voltage to LOT.  Connect a 100W 220VAC filament type bulb, to B+ and ground, using two pieces of wire and a bulb holder. Switch ON the set. Measure the B+voltage with respect to negative.  Should show around 134 to 137VDC.  If the voltage measured seem to be over than this range, check the power supply switching regulator section.  Check all the solder terminals at the power switching section, and make sure that this voltage does not exceed the limit stated above.

      If 135VDC is right, with a 100W bulb load, and set shows the over voltage indication when connected to LOT, the horizontal output section should be checked well for any short circuit.  Desolder out the horizontal output transistor (2SD-2624 CA) (Q801) from the circuit board.  Now switch the set ON and see the indication is there.  If not, make sure that the horizontal output transistor is leaky.  There may some reason for the failure to this transistor.  The first one is with shorted windings inside the LOT itself.  The second one is with loose fixation of this transistor with its heat sink, makes it overheat and get shorted.  The third one is, shorted windings at the horizontal side of the deflection yoke.

     Anyway, we have to fix an other good transistor of same type and number in place to do further check.  Replace the transistor; fix it well with its metal heat sink. Switch ON the set for a short period of time, say 3 or four seconds.  Unplug the Ac chord from wall socket, and feel the heat of the replaced transistor by bare figure touch.  It may get slight warm, but not too overheat.  If it overheats at this short period of time, make sure that the LOY (NX-4751-M3A4) is defective.  Replace the LOT with same number.  Never try to substitute any other number LOT to this set, as it may lead bad results.

     If the trouble was with horizontal output transistor only, you will get the raster within 5 seconds after you switch the set ON.

     The deflection yoke complaint is very rare, say 1 out of 1000.  If the deflection yoke has shorted windings inside it, the set will make hissing sound, and the horizontal output transistor we substitute will get shorted as soon as we switch ON the set.  We won’t get any time to detect it.