Sony IK bypassing

Sony TVs recent generations (1990 onwards), with microprocessor-controlled circuits, among other things, a circuit called IK (cathode current), which is responsible for monitoring the flow of the cathodes of the CRT (Cathode Ray Tube or kinescope).

The microprocessor circuit combined with the "jungle" (chroma-video), and a number of transistors (and other components) in the circuits for the three cathodes, are responsible for this task.

IK circuit enabled Sony TVs

From each of the video outputs (R, G, B) of the integrated circuit "jungle" three pulses are sent, one to each video output circuit. These pulses are actually three scanning lines or horizontal scan, each of which is sent to the appropriate circuit so that the cathode is activated during the scan of a line.

These lines are not visible on the screen, as they are sent over the new "sweep" vertical, in the area of ​​"blanking", but can be seen at the top of the screen is slightly reduced if the vertical height (VSIZ ) in the service menu.

This circuit also check the proper functioning of the CRT, allows automatic adjustments within the jungle IC to compensate for small differences in emission between the cathode and thus maintain the correct color of the image.

The cathode current of the circuit 3 is detected by the driver amplifiers interspersed between each of the cathodes. These circuits, send a signal proportional to the current of each of the cathodes, a buffer circuit, from where they are sent to circuit jungle.
In many teams these circuits consist of discrete components (transistors, diodes, resistors, etc..) But in more recent models, all the driver stage of the TRC (TRC video outputs or drive) and IK circuit components are included in a only as the TDA6108 integrated circuit, for example.

Almost from the moment the computer is turned on, the circuit "jungle", the respective pulses sent to each of the video output circuits, while maintaining a "cut" or "muting" video (black screen).
As cathodes reach the temperature necessary to emit electrons, the same current generates in the respective detector circuits, a pulse similar to that applied and whose amplitude is proportional to the cathode current. View image.

When the pulses reach the given amplitude IK circuit disables the "cut" of video and image displays.








IK bypass

The lack of video (black screen), Sony TV in these sometimes tend to cause confusion among technicians, because having no signal outputs of IC jungle, tend to assume that the problem is the same, as is often the case in more conventional circuit televisions.

When faced with repairing a Sony TV in recent generations (1990 onwards), which present no video (black screen), or flash and sound normal, we perform the following steps:

  1. Increase G2 by polarization SCREEN potentiometer.
     If the screen is illuminated with "raster" (sweep) normal, we can rule out any problems in the sweep circuits. (A defect in the Vertical circuit could cause the same symptom)
     This also allows to quickly check if there are voltages required for operation of the CRT (filament anode, G2).
  2. Check that the circuit receives jungle corresponding supply voltage.
  3. Check that reach the jungle integrated signals at the "micro" (clock, data).

If all this is correct, it is likely that the problem is in the driver circuits (video outputs), the TRC, or the IK circuit itself.
The next step wise, is to check the status of the TRC. If it has low emissions in one of the cathodes, or if you have internal short circuit may cause the IK is kept in "court."
For this it is advisable to use a CRT tester.
If one is not available, you can perform the following test:
With the TV momentarily placed on a resistance of about 15 to 20K 2W, between earth (ground) and each of the cathodes (KR, KG and KB), one at a time. Doing so will illuminate the display as intense, with the corresponding color.
The intensity should be similar when testing in the three cathodes. If any of the color or does not appear as faint hint of TRC is exhausted or defective.
This is not a very accurate test. The advice, as noted above, is to use a CRT Tester, however, this test helps determine if any of the guns, defective or very low emission.
Disable or "fool" the IK circuit

To determine which is the cause of a fault related to these circuits, it can sometimes be useful, "fool" the IK circuit for video Disabling this causes.
This can be achieved by disconnecting the line IK from the placing plate of the CRT and three diode type 1N4148 between the pins of integrated jungle, as shown in Fig.
This test pulses sent from the jungle IC are introduced to this again, thus blocking off video, allowing you to see the screen image.

No show image by making the change suggested, and having made the above checks, without detecting anomalies, it is possible that the jungle integrated (or any associated component) is defective.

Hope this helps to clear a bit, doubts about the operation of this circuit, and can more easily locate the cause of the failures that are usually present.

Method of deceiving the IK circuit

Another way to avoid activating the circuit IK and darken the screen when there are differences in the three cathode current is equal to connect three resistors, one to each cathode of the CRT as shown in the attached figure.




This method is rapid to implement but can slightly affect the definition of the image, which is recommended, if possible, using the method described above the three diodes.

The three resistors should be equal, and a value of 100,000 ohms (100K) or above, with a dissipation of 1/2 Watt.
The higher the value of the three resistors, less affect the quality of the image, but if it is too high you can not disable IK protection, therefore, is recommended in each case, try different values.
In some cases it has worked well using 270K resistors, in other cases it has been necessary to place resistors to 180K or 100K activated to stop the IC circuit.

ang dami ko na naman natutunan na hindi ko pa alam..ang dami pa pala akong kakainin bigas..

iyong pangalawang trick na gamit ang tatlong resistor ay napaka effective talaga ang ganyan. mas mabilis na proseso. 


courtesy of Sir Min on Elab

pa comment... abwt sa picx..
kng pansin nyu na mas mababa ang value na nilagay ni sis min sa KR (Red Gun).. ay dahil mas weak ang red gun kaysa sa dlawa... tandaan lng natin.. mapapababa kau ng resist value ay mas malaki ang effect nun sa picture appearance...

@sir ultra and @sir hertz, ang ganito po bang proseso ay ginagamit para malaman kung functional pa ba ang IK IC?tama po ba? Yung bang IK ay isang ic driver papunta sa video outputs(R, G, B)?

^ noh... ang ckt modification na yan sis vin ay para madisable ang protection ng video mute. eka nga para mabypass ang IK nya o sa mdaling salita, mabulag xa na ok raw ang operation/Emission ng tatlong mga tubes (RGBs). pg yan kasi ang ng ooperate ng tama.. at may problema khit isa sa mga GUNs like weak, shorted o open ay Video mute agad yan.. di lalabas ang images. kya sounds nlng ang matitira.. mako confuse ka saan ang problema sapagkat completo nmn ang supply sa Cboard.. mnsan mapapakamot pa tau sa ulo   ^_^

para mkausad sa troubleshooting. needed ang ganyang style sa pgdiagnose

tungkol nmn sa IK ckt sis vin. nka builtin yan mismo sa jungle/chroma.

@sis ultra tanong ko lang ang bawat pin ng isang resistor ay papunta sa rk, bk, at gk at ang another pin ng resistor nito ay ii-short mo basi dun sa nakaguhit na diagram sa taas para madeceive natin yung IK nya..Tama po ba sis ultra??  

my tanong pala dito na di ko napansin...   Sori  ^_^

ah bali. ung tatlong nakabukod na end ng tatlo resist ay feed nyu yan sa Video supply nyu (180-200V) nyu

Ask ko lng sir ultra, maari bng gni2 un s0ny na gngawa ko? Kc nwala na ang pic pg nlipat xa ng channel. S0unds na nga lng ang ntitira.

ngayun ko lang to nabasa ah, may nakita nako date ganyan yung sa crt board kaya pala
ang lulupit