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Discussion Starter · #1 ·
For a while now my KV-32HS420 occasionally has horizontally, the sides, been shrinking and expanding on it's own. Kind of like blooming, but not affected by scenes. However it has gotten worse lately.


I took it apart to see if there were any bad solder spots on any of the boards, since my Sony receiver did which I fixed, but don't see anything.


The shrinking and expanding happens on all inputs, even the tuner a bit, but most noticeably and often on hdmi with my htpc. When it is expanded is what it was calibrated at. The behavior is just sporadic any more.


I really don't have the money for a new TV atm. So if anyone has any advice, please let me know.
 

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Well..... this is usually caused by bad solders... but I'll try helping.



3 main causes for intermittent horizontal collapse


First, is the pin cushion changing when the TV shrinks? Do the sides change shape in any way?


If yes, the pin cushion transistor may be failing, either going bad (short) or has bad solders on it or in the surrounding circuit.


2nd- if pin is not affected, a failing horizontal output transistor. This can be a failing transistor but is mainly caused by bad solders on the horizontal output transformer (not the flyback). Follow the pins of the transistor and you'll find it. MAIN CAUSE OF YOUR PROBLEM


3rd- failing flyback transformer. Well, I've changed a couple flybacks in the 32"s so it happens. Needs replacement and usually costs between 25 to 70$ if you know where to look (ASTI replacements are OK)



Hope this helps
 

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Discussion Starter · #3 ·
I didn't notice the pin cushion changing until about a week ago when this got more frequent. Before I didn't notice a pin cushion change. I have my HTPC set up with a bit of underscan so it's pretty noticeable on the right side, kinda bows in.


I don't have a service manual and don't really know where the pin cushion transistor is. Can you help me locate it and possibly the other possibilities?
 

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You say it's not the scenes, but could it be the type of content you're watching? 1.66 and 1.75 aspect ratio movies, for example, will be slightly pillarboxed (black bars) on the sides. That pillarboxing would normally be hidden by the overscan on most CRTs.


No CRT has perfect screen regulation btw. If the white level (Picture control) is set too high on the TV though, that could produce more noticeable regulation issues (picture expanding in size horizontally and/or vertically on brighter scenes). A "needle pulse" test, like the one contained on DVE (Display Setup Pattern #4 on the 2003 Component edition), is designed specifically to help you keep the white level on a CRT below the threshold where that becomes noticeable.
 

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If the shrinking/expanding is severe, it points to a power supply issue. Either cold solder joints or bad capacitors. At worst, it could be the flyback transformer, but a flyback fault is accompanied by the tell-tale electric arc noise, so if you aren't getting any of that, then the power supply is the likely cause.
 

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Not sure if this'll help at all, but these are a couple patterns I devised specifically to test for "blooming" on CRTs like my Sony 34XBR800, which you're welcome to try.


These do not work the same as a needle pulse, but they should give you an idea if you're excessively overdriving the white level / Picture setting on your CRT.


For the best detail on the TV, you should keep the Picture setting below the point where the horizontal white line begins to "bloom" (get thicker) inside the area of the gray square, or starts to seperate into "two lines".


This test works best with a progressive 480p input (which I don't use on my TV anymore), with no interlacing on the screen. But the blooming should be visible on other signals as well. If the pattern is displayed in an interlaced mode (which is the way most signals other than 480p display on a Sony CRT), then the white line will be a couple scanlines wide to start with, which might be slightly more confusing.



Two versions of the pattern are attached below, one in "full 0-255 swing" levels, and another that's already been condensed to 16-235 "studio-swing" levels.


If you try these, do not leave them on the screen too long to reduce any possibility of burn-in.


RGB 0-255 "full swing" levels




RGB 16-235 "studio swing levels"

 

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A needle pulse test will probably be even less forgiving in terms of the Picture/white level setting than the pattern above btw. So the blooming test should be considered an "outside" figure for Picture adjustment that you'd almost never want to exceed.


For best PQ, ideally the Picture setting should be adjusted below the point of both blooming and any noticeable screen regulation problems (needle pulse test). The latter can be a tougher test for some CRTs to pass though.
 

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Quote:
Originally Posted by Xan /forum/post/20808374


I didn't notice the pin cushion changing until about a week ago when this got more frequent. Before I didn't notice a pin cushion change. I have my HTPC set up with a bit of underscan so it's pretty noticeable on the right side, kinda bows in.


I don't have a service manual and don't really know where the pin cushion transistor is. Can you help me locate it and possibly the other possibilities?

If you just recently adjusted the TV to underscan, then you could also be exposing pin-cushion issues that may always have existed on the TV, which were hidden before by the overscan.
 

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Discussion Starter · #10 ·
Thank you for you insight so far. I mostly watch 16:9 stuff on 1080i and that is where it happens the most and is the most noticeable. I have had the TV under-scanning for years now and didn't have this problem. The shrinking/expanding is about 1/2" each side. I have been getting an occasional noise like line lately when it happens that is a bit bigger toward the right side.


It's apart right now. So I would really like to know where on the board I should be checking and then I can re-solder and test.
 

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Discussion Starter · #11 ·

Quote:
Originally Posted by Th3_uN1Qu3 /forum/post/20818350


If the shrinking/expanding is severe, it points to a power supply issue. Either cold solder joints or bad capacitors. At worst, it could be the flyback transformer, but a flyback fault is accompanied by the tell-tale electric arc noise, so if you aren't getting any of that, then the power supply is the likely cause.

Could you show me what this may look like? I think I am getting this now. Though I wasn't for months.
 

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Caution Xan, CRT televisions contain over 10,000 volts and can give you a severe electric shock long after being turned off. You shouldn't be working on the electricals or tube of a CRT without knowing how to mitigate risks.


I agree it sounds like voltage going down and up.


There are many clips on Youtube of CRT arcing. Turn the lights off and see if there are any flashes of light from the back or popping sounds.


Bad caps often have a distictive bulging from the top. They should be easier to replace than a flyback.
 

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Then it's the power supply. First try and locate a service manual for the set. It should be able to give you a good idea where to start looking.
 
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