Convergence adjust - squeal and shutdown - Home Theater Forum and Systems - HomeTheaterShack.com

 
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post #1 of 4 Old 10-23-09, 10:32 PM Thread Starter
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boredwild
 
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Convergence adjust - squeal and shutdown

Samsung SP43W6HF has a convergence problem. In the manual convergence (service) section, Green was showing a double image in the horizontal plane in some parts of the grid. Found bad resistors on the convergence board -replaced. Auto-convergence not effective, so I had a good play with the manual convergence. By doing a massive horizontal adjustment to green I could almost get the double image to go away. TV ran for about a half-hour, then let out a good squeal and shut down - oops. Burnt a pair of 3.9 ohm resistors on the green channel that I had replaced, so I replaced again. TV still squeals and shuts down after startup, but not with the convergence board unplugged. Supply to the CG board is 28.6V on one rail and 30.2V on the other - does that seem OK or do should they be exactly the same?

Ordered some new CG amps (STK392-040) and removed the original amps. With the amps removed, the TV will run with the CG board connected, but I don't just want to chuck the new amps in and fire up. Assuming that way too much offset to the green horizontal caused the shutdown, I checked the DC offset on all channels. Adjusted them to as near to zero as I could get, but could not get red horizontal closer to zero than 320mV, and blue horizontal no closer than -260mV. Does this explain the problem with the green horizontal double image? Have I broken something in the convergence generator?

Any help appreciated, thanks.

Last edited by boredwild; 10-23-09 at 10:41 PM. Reason: measurement corrections
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post #2 of 4 Old 10-25-09, 08:51 PM
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Re: Convergence adjust - squeal and shutdown

You can normally find a range that goes positive and negative for d.c. offset when you move the position controls through their range. If you don't, then you may have the horizontal linearity, line, or point convergence so messed up that it is creating the offset. Usually, when you have a convergence generator problem you will not have control over at least some parameters or you will have a shorted op amp and get no change at all and/or a very large d.c. offset.




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post #3 of 4 Old 01-21-10, 05:09 AM
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Re: Convergence adjust - squeal and shutdown

Hi,
I have similar symptoms on my Samsung RPTV Model: SP62T6HCX/XSG Chassis: J54A

The service manual says the rails for the Convergence Board should read +20V / -20V

My set reads +24V / -24V

When I set my meter to AC voltage mode the +24V rail reads 54V
-24 V rail reads 0V

My convergence board does not have any pico fuses

No sign of any burned resistors

I reset all convergence data and have convergence data all under +/- 100 mV

Despite all of this put the new ICs in and they heated up and failed

I tried changing all electrolytic capacitors on the power supply board

Now the +24V rail reads 54V
-24V rail reads 54V

Now the STK ICs are rated +/- 50V max could this be the reason they are blowing

Any help would be appreciated.
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post #4 of 4 Old 01-21-10, 05:32 PM
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Re: Convergence adjust - squeal and shutdown

You are already being helped in another thread. Please do not double post problems and do not corrupt other threads with issues with a different model.




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