I have a Teac ctm805sr tv suffering pincushion

Description: The task involves repairing a television, specifically identifying the area on the schematic related to the pincushion circuit, which appears to be the primary issue. Initial inspections revealed some dry joints and poor soldering that were addressed, but these repairs did not resolve the problem. It is suspected that a component may have been failing and has since completely failed. The lack of schematics for this particular model complicates the troubleshooting process. It is noted that if Q405 is shorted, the picture may display an hourglass shape, while an open or undriven transistor could result in an oversized image.

The pincushion correction circuit in a television is essential for maintaining the proper geometry of the displayed image. This circuit compensates for distortions that occur at the edges of the screen, ensuring that the image retains its intended shape. When troubleshooting a pincushion issue, it is vital to focus on components such as transistors, resistors, and capacitors within the circuit.

In the absence of the specific model's schematic, it is advisable to locate the pincushion circuit, commonly found near the deflection yoke or the video output stage. The component Q405, a transistor, plays a significant role in this circuit. If Q405 is shorted, it can cause severe image distortion, specifically an hourglass effect, where the image appears pinched in the middle. Conversely, if Q405 is open or not properly driven, the image may be oversized, leading to a loss of clarity and detail.

To further diagnose the issue, the following steps are recommended:
1. Inspect the solder joints around Q405 and related components for any signs of cold solder or cracks.
2. Test Q405 for continuity and proper operation using a multimeter. If it is found to be defective, replacement is necessary.
3. Examine surrounding components, including resistors and capacitors, for any signs of damage or degradation, as these can also contribute to pincushion distortion.
4. Utilize an oscilloscope to monitor the signals at various points in the pincushion circuit to identify any abnormal waveforms that could indicate faulty components.

This systematic approach will aid in accurately diagnosing and resolving the pincushion issue in the television.Fixing a television (as it was given to me). I am hoping to find at least which area on the schematic is related to the pincushion circuit, as this seems to be the only problem with the tv. The first thing I checked was for dry joints or poor soldering. I fixed a couple, but they have not helped, and because of the way the picture went, I would assume that a part was failing at the time, and has now failed completely.

I do not have schematics of this particular model then I would be in better position to find out pincushion problem in your TV. Let me know your findings. If Q405 is short, picture would be hour glass look and if this transistor is open or not being drive, picture would be over sized.