Re: Does the TOSHIBA TA8445K Vertical Deflection IC fails...
Hola tengo un tv onwua que no me habre el verticar ya revise los voltajes y estan bien pero en la pata 11 tengo solo 7 voltios en ves de 12 voltios cual puede ser el problema de mi parte muchas gracias.mi email es firstname.lastname@example.org.
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Absence of horizontal scan signal to the deflection yoke. Check all the connection to the deflection yoke. If found OK, the deflection yoke winding [horizontal] is open. If you wish to get some details; check the site linked here. Pull up older posts. Surf the site with patience. http://electronicshelponline.blogspot.com/
A single horizontal line means that you have lost vertical deflection. High voltage is most likely fine since there is something on the screen.
This could be due to:
Dirty service switch contacts. There is often a small switch located inside on the main board or perhaps accessible from the back. This is used during setup to set the color background levels. (On some sets, this is located on the CRT neck board and may be a jumper plug or other means of selecting service mode - not an actual switch.) When moved to the 'service' position, it kills vertical deflection and video to the CRT. If the switch somehow changed position or got dirty or corroded contacts, you will have this symptom. Flip the switch back and forth a couple of times. If there is some change, then replace, clean, resolder, or even bypass it as appropriate.
Bad connection to deflection yoke or other parts in vertical output circuit. Bad connections are common in TVs and monitors. Check around the pins of large components like transformers, power transistors and resistors, or connectors for hairline cracks in the solder. Reseat internal connectors. Check particularly around the connector to the deflection yoke on the CRT.
Bad vertical deflection IC or transistor. You will probably need the service manual for this and the following. However, if the vertical deflection is done with an IC, the ECG Semiconductor Master Substitution guide may have its pinout which may be enough to test it with a scope.
Other bad parts in vertical deflection circuit though there are not that many parts that would kill the deflection entirely.
Loss of power to vertical deflection circuits. Check for blown fusable resistors/fuses and bad connections.
Loss of vertical oscillator or vertical drive signals. The most likely possibilities are in the deflection output stage or bad connections to the yoke
Check the deflection yoke connection cable for any loose contact at its connection socket at main board side. Unplug the connector out from the socket, and re-plug it back for at least tow times. Check the solder terminals of all connections to horizontal output. It will be best to re-solder all suspected solder terminals there. [horizontal sweep signals to the deflection yoke is absent now. Only vertical sweep is present now]
A vertical line means the line is up and down in the middle of the screen. That would indicate that the vertical IC and the surrounding components are working perfectly. A vertical line as described is the result of a lack of horizontal deflection (to move the beam from side to side) Since the high voltage is obviously OK, the problem is most likely a bad solder connection in the horizontal yoke circuit. Examine the bottom of the PC board in the area of the flyback transformer, and yoke connector (has four wires Red, Blue, Green, Yellow).and the pincousion coils, capacitors, etc in between. Flexing the board in that area may cause the problem to come and go. Resulting arcing should also be visible. BE CAREFUL, as hazardous voltages are present in the circuit!
It could be the vertical output IC, but there may be other possible causes which include:
- bad solder contacts on deflection yoke connectors or dirty connector contacts (on the circuit board and / or on the picture tube neck)
- bad solder contacts on the vertical output IC or associated components (check for little cracks in the solder around the pins, these are so called "cold" or bad / broken contacts)
- power loss to the vertical output IC - check for any burned resistors or other components around that IC, assuming you know which one it is - see which ICs are connected to the wires going to the deflection yokes (coils) on the picture tube neck and check them well.
You need to resolder any bad contacts, clean any dirty pins on the connectors and replace any burnt out components (assuming you can still determine the type or value of the component).
Since you mentioned the problem occurs once in a while, this means that the IC probably fails when it warms up, which can often happen if there are loose connections or bad solder contacts.
Anyway, it could turn out to be a faulty IC, i just suggested a few other things that can be fixed quite easily, and possibly without the need to replace any of the components.
This denotes a problem with the vertical deflection circuit. This is more then likely the result of the vertical coupling capacitor failing. You will need the schematic diagram of the TV to find the capacitor in question. it is located between the vertical output stage and the vertical deflection winding of the yoke transformer. In addition check the continuity of the vertical winding of the yoke transformer this can cause the same problem. In any event the problem is that the vertical deflection signal is not getting to the yoke transformer or the yoke transformer is malfunctioning.
This is a vertical deflection problem, These are the possible causes:
1) bad vertical coupling capacitor 2) bad vertical output IC 3) bad vertical driver IC 4) bad CRT deflection yoke
Troubleshooting needed: 1) using the TVs schematic locate the driver IC the output IC and the CRT yoke transformer. 2) using an oscilloscope look at the vertical driver signal it should be a sawtooth signal from the driver to the yoke (increasing in amplitude for each section, i. e. driver and output). 3) if no sawtooth patter is seen that is your problem, look for the component in the section where signal is entering but nothing is coming out. 4) replace the components
Now let me tell you something, don't continue to play the TV with the line present with brightness applied, this will burn the image of the line into the phosphorous coating of the CRT.
Defective components in vertical deflection and output circuit inclusive of vertical output device, coupling capacitors, and yoke connectors. Passive devices such as electrolytic capacitors, coils, and resistors to/from power supply circuits. If your tele is more than 10 years old dump it and get a newer product. $100 USD is a fair price to diagnose and attempt service, depending on age and configuration. Older products may not have replacment
parts available at any repair cost.
There may be a pot for adjusting the vertical size. If so, it may be dirty. If you can find it, try adjusting it which could clean it. BE CAREFUL -voltages are very high.