JVC AV65WP74 Convergence Problem - Home Theater Forum and Systems - HomeTheaterShack.com

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post #1 of 5 Old 11-05-12, 03:37 PM Thread Starter
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Jeremy Hedlind
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JVC AV65WP74 Convergence Problem

Hello everyone. I created the following post yesterday evening about a problem I am having with a JVC AV65WP74 model rear projection television.

"I have a JVC AV65WP74. Originally, the television had a convergence problem. I sent the board off for repair to Startboy1010 on Ebay. He replaced the STK392-110's with STK392-120 IC's. It does not appear that he changed any of the resistors when he did this. After reinstalling the board, the television image was very distorted. See picture 1. It looks like the overall image is wavy.

At this point the magic focus button, and the auto convergence in the menu run, but they don't make any change. The manual convergence feature in the regular menu will not respond.

In the service menu, (I acquired the service menu from startboy1010), it says to turn off the convergence adjustment (f62 from 0 to 1) and then do all of the deflection adjustments manually.

This is the point where I am stuck. I am cannot get the deflection to set normally. The image is badly convex at the top, bottom, left, and right. I cannot seem to adjust it out. It has been suggested to me that there is another problem with the television. However, I can't believe that to be true because before removing the convergence board for repair none of these other symptoms occurred.

Is it typical to have to redo all of the deflection settings and all of the convergence manually once the ic's are replaced on a convergence board? Or should I go back to my original thinking that the repair is no good. Does anyone have the spec sheet for the STK392-120's so I can compare it to the specs for the 392-110 and see if they are identical. I would think that at least some of the resistors should be changed to accomodate differences in the amp design."

I received this response.

I suggest starting a new thread specific to your problem. You will need to start from the beginning and troubleshoot the problem. I suggest restoring the set to the original state for all settings, read the convergence sticky above very carefully, and test the resistors and power to the ICs. You may have an open fuse in the power supply or you may have an ineffective repair. Hard to tell at this point.

1. I read about the first fifteen pages of posts on troubleshooting a convergence problem with this television.

I have the following questions.

1. Does anyone have the spec sheets for the STK 392-110 convergence amps so I can compare the specs to the STK 392-120 and see if they are 100% compatible? Or, can someone confirm they are identically compatible and no resistors would have to be changed to allow them to operate properly.

2. I will check power to the IC's tonight. I have the spec sheets for the 120's so I can confirm they are receiving the proper amount of power this evening. I will post my results.

3. I have tried resetting all the settings back to the default setting. It does not seem to make a great deal of difference. It changes the picture on the screen, but it never gets anywhere close to a reasonable image.

4. I doubt the fuse theory, because before this board was repaired, there was only a slight problem with the convergence on the blue being off. Now everything is terrible.

5. I have tried to set the convergence manually by entering the service menu, turning off the convergence, (F62 from 0 to 1) and starting to set the delection settings. The television will not respond to all of the commands requested in the deflection settings. Some persistent problems are that the television produces a wavy overall image with all three colors out of alignment. Additionally, I am unable to eliminate the bowing at the top, bottom, left, and right of the screen which makes the image appear convex. I have been able to adjust horizontal height, width, and centers in both directions. But the projected image is far from rectangular so it is impossible to make these adjustments correctly.

6. I can check the resistors around the ic's tonight. I was told by the person who replaced the ic's that the board was tested good. What does that mean? How can he properly test the board outside of the television?

I can pull the whole assembly from the television and set it up to be tested with a signal gen, and a scope. But, I don't know what data I should be inputting to the television via the signal gen. Also, I don't know what waveform I should be looking for on a scope. The service manual does not provide these procedures.

I think the best thing for me is a suggestion on how to proceed from this point.

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post #2 of 5 Old 11-21-12, 10:41 AM
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post #3 of 5 Old 11-21-12, 01:39 PM Thread Starter
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Jeremy Hedlind
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Re: JVC AV65WP74 Convergence Problem

No, I have not made any significant progress.

The deflection amps are getting power.

I am stuck at the adjustment page I am attaching to this post.

I am also attaching the complete service manual so someone can have a better understanding of what I am dealing with.

I am at a loss as to how to proceed.

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post #4 of 5 Old 11-22-12, 09:42 AM
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Re: JVC AV65WP74 Convergence Problem

It sounds like you have no correction at all. If you have power to the output ICs then I would look to connections from the convergence generator to the output board. The system may also be in convergence muting. Look in your schematic for a mute line.

The "confusion" document describes beam forming and focus and has nothing to do with convergence. The only thing you should be doing with magnets for convergence is centering the position. These are on the deflection yokes, not the focus rings.

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post #5 of 5 Old 11-22-12, 11:54 PM Thread Starter
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Jeremy Hedlind
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Re: JVC AV65WP74 Convergence Problem

Turning the setting F62 from 0 to 1 turns the convergence off. I can do this and it definitely changes the image that appears on the screen.

It goes from a distorted misaligned picture to a screen of white noise with two vaguely identifiable circles, one on the left and one on the right.

The reason I am attempting to start from the beginning with the television is that it appears every adjustment is completely out now. I've reset all of the digital adjustments back to their default values. The flowchart in the manual describes starting from the beginning and redoing every adjustment when a component is replaced.

I will double check the connections again, but I have done this before and been unable to locate a problem.

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