CRT KR & KG Sort

Hi
Your tv set should be serviced. Firt step check the filament voltage. Schematic can be necessary. If it is OK, check the screen voltage at the pcb attached to the CRT neck. If it is missing, check the resistor and the decoupling poliester capacitor.
In some tv models, when one color gun is faulty the CRT shuts down for protection. Then RGB output voltages should be checked to trace the faulty one.

Sully

Hello

The red colour output section in your TV has some short in it. This section can be located at the picture tube base card, the printed circuit board along with some components are fitted with it. There will be three cathodes, Red, Green and Blue; usually marked as Kr, Kg and Kb. Take the voltages of these pin points at this board. It should be almost the same. In your TVs case, the voltage at the red cathode will be very low now. Look whether transisotrs or Ic is used for video output section in this side. Usually Sony uses transistors. Check the resistor at the collector of red output transistor. If it is open, replace it. If the resistor is OK and still there is no voltage, and the said resistor heats up abnormally, the transistor related to it is leaky [collertor-to- emitter short]. Replace it with same type and number will solve your problem. OK.

Hello

There are two causes for this problem. One is related with green output transistor, and the other is to chroma Ic. The most common cause is with the transistor said above. You just check the video output voltage points at picture tube base board. There are three cathodes may be marked as R,Gand B. In trinitron picture tubes, these pins are pin number [8 Blue KB], pin number [9 Green KG] and pin number [10 Red KR]; and the voltages must come approximately equal to KR=154, KB=155, and KG=163, and the main video output voltage goes to these transistors will come around 225VDC. These are not accurate voltages tor refer. It may vary by 2% to set by set. All the three transistors used will be identical in number, and usually found 2SC3271N. In your TVs case, green cathode voltage may be very low from the fault stated above I thinks. When cathode voltages goes low, emission of that cathode will increases, and colour of that cathode will be predominent. You just check these voltages, and check the main video input voltage said above too. There are three resistors of 2W fitted to the the main video voltage and collector of each transistor said above; and if any one,say the resistor fitted to green output transistor collector is faulty, or open or loose sodered, the voltage at the green cathode [pin-9] will be low causing this problem. If the transistor said above gor a leak with collector to emitter will also may the cause.
Just check it. Normally this base card of Sony TVs are marked C board. If all the transisors are found okl, and still the problem perisits, the fault must be in the Chroma Ic. It may need replacement.
In practice,I found this fault to be due to bad solderings in the base card. You just check it first and go forward.
If any doubts, contact me through Fixya. OK.

let us be sure first if the power of your tv is on.
1.do you hear a sound coming from your tv?
2.is the remote sensor of your tv is responding once you press a button?
if the answer is yes then your tv is on!
to fix the problem, open the back cover of your tv.once it is open plug it to your wall outlet and power on.be carefull not to touch the live components of your tv..there is a small pcboard that is plug in to the end of the picture tube it is called the crt board or the cathode ray tube/tv color amplifier.At this board you can see the crt socket that connects the picture tube and the CRT board
the crt socket has labels on pins they are KR,KB,KR,and H1,H2.

apply fresh solder from CRT board. chek transistor red color amplifier. KR, KG, KB. check voltage DC.

necesito el diagrama de la fuente del rca

Hi,

I am assuming that this is a conventional CRT type TV. Most if not all TVs of this design has a small squarish PCB right at the very rear of the tube encased in a shielding of some sort. There would be three (3) transistors in said PCB responsible for driving the 3 color guns of the TV (red, blue & green). In some instances, it could just be a single power IC. Either the transistor or the IC would be heatsinked. The transistor for the red color is defective and would require replacement (if IC then the whole IC). In some instances, it could only just be a cold solder.

This of course would require a fair familiarity of electronic components/circuitry and safety procedures, use of a DVM and a soldering iron. It would be to your added advantage access to a service manual or at the very least a schematic diagram with voltage readings. Should you be uncomfortable performing a DIY (do-it-yourself), perhaps your best bet would then be to seek the services of a qualified professional.

Hope this be of initial help/idea. Pls post back how things turned up or should you need additional information.

Good luck and kind regards. Thank you for using FixYa.

if its the board that attaches to the center gun its called green crt pcb

On the CRT itself, without the socket connected, you should have continuity (0 ohms) between G1, G1-2 and G1-3. Those 3 pins are Grid 1 and are tied together inside the neck. You should also have continuity (maybe 5 ohms or so) from H1 to H2. Those 2 are connected to the 3 heaters (in parallel). When the set is on there will be 6.3 volts of high-frequency AC power at those pins, and you should NEVER try to pump more voltage to the H pins. If you clear out the continuity between the 2 H pins then you blow open all 3 filaments and the set is garbage. There should NOT be continuity of any kind between G2 and any other pin. If there is then the tube is bad and cannot be fixed. There should also be no continuity at all between any other pins. The good news is that from the voltages you posted, you have a heater-to-cathode short that developes in the green gun when the tube is warm. To remove this short, take a 22uF 250V capacitor and put an alligator clip from the negative lead to ground. Connect the positive lead of the capacitor to the 200 volt boost source and turn the set on, which charges the capacitor. Tap lightly on the neck of the CTR and when the voltage drops on the KG pin, the screen will go quite green and that is when you should take the positive lead of the charged cap and touch it to the KG pin on the tube socket. This should remove the heater-to-cathode short. A 22uF cap has enough charge to clear the short but usually not enough to blow open the filament itself. Using a capacitor larger than 22uF runs the risk of blowing the filament open and you do not want that. It is tricky to get it right because you have to have a charged cap and the tube must short out and you have to get the charge from the cap into the tube before the set shuts itself down. Try that and post your results.

The problem you have lies either in the CRT or the CRT card. If you are familiar with the term Video B+, check this voltage at the collectors of each of the output transistors on the CRT card. You should read about 175 volts or so at each collector. You will probably find that the voltage on the collector for the GREEN output transistor is low. If so, pull the CRT card off the CRT (with the set off to prevent any arcing) and double check that collector voltage again. If it is back to normal, then you can suspect that there is a short of some kind with the GREEN gun in the CRT.