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MAC944turbo



Joined: 26 May 2006
Posts: 4

PostPosted: Fri May 26, 2006 11:47 am    Post subject: Picture squeezes horizontally Reply with quote

I got a TV that was said to have problems but after plugging it in and turning it on it was fine. I watched about 2 hours of it immediately after I had just plugged it in. The next night I turned the Tv on and within 30 seconds of watching it the image began to gradually squeeze/compress itself horizontally sometimes unsqueezing then finally squeezing itself down to about a 2-inch line across the screen. I quickly turned the TV on and off as I heard this will help degauss it, and the first time that this problem occurred and I did this the image went back to normal. But after 10 seconds the image once more gradually compressed down to the 2 inch line, the image can still be seen only its squeezed. I let the TV sit unplugged for 2 hours, I plugged it back in, turned it on and got a perfectly good image for about a minute until the problem began again. After it had sat plugged in for a night and the problems began leads me to think that it may have something to with the capacitors, because after leaving the Tv unplugged for 2 hours and then using it again i got a good image for a minute, and like I said when I got the TV it had been left unplugged for a long time it gave me no problems once I plugged it in. I believe once the capacitors have been left to discharge it will work fine but once the capacitors fully gain their charge the problem occurs. leaving the TV unplugged for those 2 hours i think let the capacitors discharge a bit and I was able to get a little bit of time of normal viewing, and the first time I plugged it in I believe the capacitors were completely discharged and thats why i was able to get a good image for 2hours but the next night the problem began. Thank you very much for your time and hope to hear from you soon.

Mark
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sparky



Joined: 18 Nov 2005
Posts: 98
Location: U.K

PostPosted: Fri May 26, 2006 5:21 pm    Post subject: Picture squeezes horizontally Reply with quote

Make and model of set would normally be required for more detailed diagnosis.
With the set unplugged remove the back cover and look for bad solder joints (If solder joints the verical i.c or scan coil plug/socket joints are usually the cause and the i.c normally has about 9 pins on it attached to the metal chassis for cooling and MAY start with the letters TDA) or reconnect and switch on. Using a plastic instrument prod the main circuit board with one hand in your pocket to see if you can instigate the fault (be very careful not to touch anything due to dangerous voltages including the metal chassis with fingers as this may be live). If the fault is made to come and go then would be likely to have a bad solder joint in the vertical output circuit otherwise a electrolytic capacitor in this circuit may be the cause as these capacitors if faulty values tend to decrease as they heat up providing the symptoms obtained.
Note if the set does have a bad solder connection then the vertical output i.c will eventually die so could be argued prodding is not really a good idea but admittedly I sometimes do for quickness or the cabinet tap test.
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MAC944turbo



Joined: 26 May 2006
Posts: 4

PostPosted: Fri May 26, 2006 11:59 pm    Post subject: Thanks for the help Reply with quote

OK first off it's a 27" Mitsubishi CS-27205, I wouldn't really want to go ahead and prod around but I do know someone who does this for a living and would let him fix it since I got the TV free of charge. I only wanted to provide maybe a basis for him to start or since he does this for a living he may already know what the problem is once I give him the TV. thank you very much for you help and I strongly do feel that it may have something to do with the capacitors as it worked fine when left unplugged for a long time as I said in the post. Just another quick question what would it take to fix something like this, say if it was simply a capacitor or two? Not much as I figure they are relatively inexpensive probably under $20 per capacitor?? And also what if it were the Vertical IC how much would this cost, I don't mean the transisitor that usually goes I mean the actual board or chip that the Vertical Output is on. Thanks again to all especially to those who have posted a reply, I await your reply once more.

Mark
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sparky



Joined: 18 Nov 2005
Posts: 98
Location: U.K

PostPosted: Sat May 27, 2006 8:11 am    Post subject: Picture squeezes horizontally Reply with quote

Depends on time spent but I would say in the U.K approx £50 total or $93 with current exchange rate although I couldn't really speak for colleagues in the U.S. Capacitors are general purpose components and less than a Dollar but the i.c would be more expensive especially if it had to be ordered as additional costs involved in this (if any) would be passed on.
If it could not be repaired quickly a service manual may also be required and at least some of the costs for this may also have to be passed on to the customer. These are good reasons to take to a dealer as information and spares are readily available including the experience and training of a particular brand (shortening time spent) as the dealer has manufacturer support but unfortunately Mitsubishi in the U.K no longer make sets. I can heare some of you laughing. Laughing
Hope this helps.
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MAC944turbo



Joined: 26 May 2006
Posts: 4

PostPosted: Sat May 27, 2006 9:21 am    Post subject: Thanks again for your help and info Reply with quote

Sparky thank you very much for your time and help, just a few more questions if you don't mind: I am going to try and see if the capacitors are at fault, i know they hold a lethal charge and have some knowledge on how to discharge them by using a 5-ohm resistor or something along those lines I can't remember off the top of my head but I can get to the correct info. Now my question is how can I check to see if a capacitor is faulty, I'd have to measure the voltage while the TV is on and the back is off correct? I have an analog mutlitester with ACV, DCA, DCv and OHM selections, I'm guesing I'd be using ACV set at the highest setting (1000) or next setting (250)?? Is this how I can detect a faulty capacitor or could a positive result of a faulty capacitor be only a cause of a different component?? I have some experience in electronics, my latest one replacing the fuse on a Lilliput 8" LCD/TouchScreen, and while i was using it for the first time my AC adaptor decided to blow a resistor but i didn't know that so I thought the fuse inside the LCd had blown i reopened it after much hard work of having put it all back together even dissasembled the whole setup i had going (a 5X20mm 1.5a fuse set in place with hot glue to the wires and the wires soldered to the tiny blown fuse. I'll get around to putting in the correct tiny fuse in there once i get it shipped here) . anyway so my point is I actually would be comfortable replacing the capacitors I just want to make sure of two things: one that it really is the capacitor and 2 that I dont die. Thanks a lot for all your help and again i hope you can help me out and respond to my myriad of questions.

Mark
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PostPosted: Sat May 27, 2006 9:49 pm    Post subject: Reply with quote

You test capacitors with an ESR meter with the set UNplugged. You never work on live equipment unless it is the last resort. There could be 30 000 Volts in there with the set unplugged.
With the set unplugged you may be able to test the electrolytics on the ohms scale of your meter, the needle should move up and slowly back as the capacitor charges. If the needle does not move, the capacitor may be open circuit or it may just be too small. If it reads zero ohms it may be short circuited.
With the set unplugged, why don't you study the solder joints around the verticle IC with a magnifier? Or resolder all of the connections around the verticle IC and replace all of the electrolytics in this area? Use good quality high temperature replacements (105 degrees C) Make sure you put them in the correct way around.
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MAC944turbo



Joined: 26 May 2006
Posts: 4

PostPosted: Sat May 27, 2006 10:43 pm    Post subject: One more question... Reply with quote

I don't understand though, if the Tv is unplugged wouldn't the capacitors be uncharged? I've left the Tv unplugged for a few days so I can let the residual charge dissipate but I hear it can stay there for days or even weeks, so I'm not really sure I understand why the needle should move up and slowly back as the capacitor charges if the tv is unplugged??? Thanks again to all who have helped.

Mark
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PostPosted: Sat May 27, 2006 11:07 pm    Post subject: Reply with quote

Your meter has a battery in it. On the ohms scale, current flows from it into the capacitor the needle moves up. When the capacitor is charged with the battery voltage the current stops flowing and the needle moves back. If you swap the leads around you can see it happen again.
An ESR meter, Equivalent Series Resistance meter, measures the internal resistance of the electrolytic capacitor which is the most important parameter. An old capacitor with high internal resistance will give you problems even if a capacitance meter says it is in spec.
If the capacitor was charged you would blow up either of these meters.
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PostPosted: Wed May 31, 2006 8:29 pm    Post subject: Reply with quote

This may be of interest to you.

http://www.repairfaq.org/sam/safety.htm
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PostPosted: Thu Mar 29, 2007 4:47 am    Post subject: Re: Thanks for the help Reply with quote

MAC944turbo wrote:
OK first off it's a 27" Mitsubishi CS-27205, I wouldn't really want to go ahead and prod around but I do know someone who does this for a living and would let him fix it since I got the TV free of charge. I only wanted to provide maybe a basis for him to start or since he does this for a living he may already know what the problem is once I give him the TV. thank you very much for you help and I strongly do feel that it may have something to do with the capacitors as it worked fine when left unplugged for a long time as I said in the post. Just another quick question what would it take to fix something like this, say if it was simply a capacitor or two? Not much as I figure they are relatively inexpensive probably under $20 per capacitor?? And also what if it were the Vertical IC how much would this cost, I don't mean the transisitor that usually goes I mean the actual board or chip that the Vertical Output is on. Thanks again to all especially to those who have posted a reply, I await your reply once more.

Mark
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