No Color

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  #1  
Old 07-10-14, 01:29 AM
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No Color

This is a very old Sharp Color TV. Model Is C-2091G. No remote Controler for this model. I switched on this TV after 3 years. Now the picture is black and white. Sound is ok. Sometimes color comes and goes. This tv can not be connected with a video player directly. I used AF-RF converter to connect a DVD player to the tv antenna port. But that picture is also Black & White. I checked video section and CRT neck board and re-soldered some joints. I replaced some electrolytic capacitors in the video section also. But no any difference. Could somebody help me.
 
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Old 07-10-14, 01:51 AM
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Welcome to the forums.

As we are based in the States I'm afraid we wont be of much help to you in your quest there.
It may be time to retire that tube set. You don't even use the same video format that we use here.
 
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Old 07-10-14, 05:43 AM
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That's a common problem in the old sharp tvs. To fix it requires an adjustment of a coil in the video circuit. If you post a pic I can point it out to you. It will be next to the largest IC on the main board. So get a close up pic of that area.
 
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Old 07-11-14, 12:55 AM
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Re:No Color

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Thank you for replying. I am sending a pic taken around the chroma area in the main board. The pic shows the largest IC in video and chroma section. Also I found that a Resister in the crt neck board (390K 1W) has gone to value about 415K when checked with VOM. And when checked with DMM it does not shows a steady value. Value is about 488K but slowly reduces. Do I want to replace it. Hope your reply.
 
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Old 07-11-14, 01:16 AM
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Are you thinking of the color oscillator coil (3.58mghz) ?

This TV is in use in a different country. I don't think they use the NTSC system is Sri Lanka

Value is about 488K but slowly reduces. Do I want to replace it.
You can't check it "in circuit". You'll need to lift one end because your meter is charging a capacitor and changing the reading.
 
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Old 07-11-14, 01:24 AM
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Actually in looking at the board.... that is the chroma chip and I circled the crystal that controls the color.

I just don't remember which one of the three coils I'm pointing to is the correct one.

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Old 07-11-14, 02:53 AM
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Yes. i removed that resistor from the board. Then I found that, that Resister in the crt neck board (390K 1W) has gone to value about 415K when checked with VOM. And when checked with DMM it does not shows a steady value. Value is about 488K but slowly reduces. Do I want to replace it. Hope your reply.
 
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Old 07-11-14, 03:00 AM
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Re: No Color

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Is this pic is clear? Can you show the exact coil pls? Or would I adjust all the coils you showed and test?
 
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Old 07-13-14, 06:02 AM
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Don't worry about the crt board. If you use a jewelers screwdriver ( flat head ), with the tv pluged in and turned on to display a channel. Just touch the screwdriver to the inside of the coil,don't turn anything. Watch the picture for the color to come back on or you may just get color bars scrowling through the screen. That will be the coil to adjust. There will only be one that should do that. When you find the one , it will require just a small ajustment up or down.
The set will be live so be carefull about touching anything else due to shock hazard.
 
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Old 07-31-14, 06:04 AM
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Re: No Color

This is related with the above problem and with the same TV set.

I Tested some components (resisters) in the Video and Chroma section by de-soldering them. There were no any faults in those components. Then I re-soldered them. But Now the set does not work. it does not give any picture even though the good antenna cable is connected . It is now like this.

Attachment 35592

Then I checked the circuit board again and saw that I have made a solder bridge accidentally. Then I remove the solder bridge. The bridge was there as shown in the following picture. I have circled the location.



Then I again switched on the set but there was no any difference. No Video. I gently hit the board with wooden stick to check whether there is a solder crack. But No any change happened. I think I have damaged the Video IC or Chroma IC because of the solder bridge I made. Do I want to replace those two ICs? The small IC shown in the picture is video IC and large one is the Chroma IC. I am a beginner for a TV repairing. Hope your advice as you are a genius. Thanks.
 
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Last edited by Thirantha; 07-31-14 at 06:25 AM.
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Old 07-31-14, 06:31 AM
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Re: No Color

This is related with the above problem and with the same TV set.

I Tested some components (resisters) in the Video and Chroma section by de-soldering them. There were no any faults in those components. Then I re-soldered them. But Now the set does not work. it does not give any picture even though the good antenna cable is connected . It is now like this.

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Then I checked the circuit board again and saw that I have made a solder bridge accidentally. Then I remove the solder bridge. The bridge was there as shown in the following picture. I have circled the location.

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Then I again switched on the set but there was no any difference. No Video. I gently hit the board with wooden stick to check whether there is a solder crack. But No any change happened. I think I have damaged the Video IC or Chroma IC because of the solder bridge I made. Do I want to replace those two ICs? The small IC shown in the picture is video IC and large one is the Chroma IC. I am a beginner for a TV repairing. Hope your advice as you are a genius. Thanks.
 
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Old 07-31-14, 08:41 AM
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It's one thing to be able to service TV's like we do..... it's a completely different thing for us to tell you what to do. We have all kinds of equipment we use for testing.

That old set is not likely to have an intermittent solder problem. In the picture below that you posted - the TV is out of horizontal lock. It would be very rare to find a defective resistor causing your color problem.

We instructed you what to do in previous posts..... did you try it ? You didn't acknowledge us.

The TV uses a crystal to hold the color burst oscillator on frequency. If the crystal drifts off frequency you'll get a b/w picture with no color.

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Old 07-31-14, 10:54 PM
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Re: No Color

Yes. I wanted to try as you instructed. When I connected the board to the crt I faced to this new problem. Hence I could not try as you instructed. Earlier It was working fine. At that time only problem was intermittent color problem. No the situation is worse I think. Sound is Ok. But video is like the picture I posted. Have I blown any component because of the solder bridge I made? So please tell me what to do now. What section should I check? There is a variable resistor called H-Hold. Can I set the Horizontal Lock with that Variable Resister. I like to learn Tv repairing. Hope your reply.
 
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Old 08-03-14, 04:48 AM
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Thank you. As you said that problem was loss of Horizontal Lock. There is variable resister for H-Hold. I slightly rotate it and, it solved the problem. But picture is still b/w. I tapped every coil with a screw driver as instructed by craftsman_50. But color bars were not visible. I slightly rotated the coil near the chroma chip as instructed by the craftsman_50. But No any change happened. Do I want to replace the crystal? Here in Sri Lanka we have PAL System.
 
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Old 08-03-14, 07:44 AM
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The idea was not to tap the coils. Place a jewelers screw driver inside the coil touching the core . This will change the coil with out moving the adjustment to see if it makes the color change. Since the correct coil is unknown, this will let you find the one that needs adjusting with out causing any problems by adjusting the wrong one.
 
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Old 08-04-14, 01:14 AM
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Thanks for replying. Yes. I touched every coil you mentioned. But there was no visible color change. Then I slightly rotate one coil near the chroma section. But then also there was no any change. I asked from a local tv technician and he inspected the board & told that this may due to insufficient power supply problem. He further told that H-out transistor has been replaced earlier by someone and and has been replaced with different transistor. He told that it has been replaced with BU208D. But Original Transistor number should start like 2SC..... as its power regulator transistor is 2SC2365 and this is a Japanese set. He told that slight rotation of B+ Adjustment knob may solve the color problem or I have to find the correct replacement. Is there any truth of it? If it is true, Then what will be the exact H-Out transistor for this set as I do not have the circuit diagram. How to find that exact number? He finally said that if it does not cure the problem you should replace Crystal, Video IC & Chroma IC. Hope your guidance. Thanks.
 
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Old 08-04-14, 05:46 AM
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The set has been working fine with the sub parts in it , so I would disregard the information he gave you. The only thing to do now is find a service maual for the set ,so there is no guessing on what each part is doing.
 
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