CRT TV Board Replacement

[Thirantha]

This is a old sharp 20' inches crt tv with no remote control facility. TV Model No is C-2091G. I want to replace the board of the TV as there is an unrepairable fault in the board. I have seen there are crt tv boards available in the market for cheaper prices. (Sri Lankan Rs. 2600/- ). Will I able to replace this tv board with that kind of a new board? Usually they show those boards for customers by plugging the board to 14' inches crt. But they also say that those boards can be fixed to 14 - 21'' inches TVs. Can I use that board to this 20' inches Tv? Then what are the factors I should consider when buying such a board for this tv?

 

[davenn]

without knowing the actual fault or anything about the board compatibility
that question cannot really be answered

Dave

 

[Thirantha]

without knowing the actual fault or anything about the board compatibility
that question cannot really be answered

Dave

The problem with the original board is the picture is B/W. No color. The fault is with the chroma filter (Z0302CE 230V). But it is not available in the market. Therefore I need to replace main board and crt board with a general board available in the market. How do I know that the new board support the CRT?

 

[davenn]

you would have to ask the manufacturer or some one who has done servicing on that model

 

[KrisBlueNZ]

Wouldn't it be easier to take the chroma filter from the new board and put it on your existing board?

Edit: Ask the seller of the new board to tell you the part number of the chroma filter, and if it's the same as the one on the board you have, buy the board, remove the good chroma filter from it and transplant it into your board.

 

[davenn]

yeah ... I didn't think of that Kris

 

[Thirantha]

Wouldn't it be easier to take the chroma filter from the new board and put it on your existing board?
Edit: Ask the seller of the new board to tell you the part number of the chroma filter, and if it's the same as the one on the board you have, buy the board, remove the good chroma filter from it and transplant it into your board.

There is no such a filter in the new board. The following picture shows that filter in the original board (The large silver color rectangular one). That kind of a filter is not available in newer boards

[Edit: I fixed your quoting so your post looks right, and undeleted it. -- KrisBlueNZ]

 

[KrisBlueNZ]

Oh.

Do you have a schematic for your original board?

Have you removed the filter from the board and measured it?

Do you know exactly what is wrong with it? Is there an open circuit winding? Is the adjustable core broken?

Have you looked inside it for obvious damage?

 

[davenn]

There is no such a filter in the new board. The following picture shows that filter in the original board (The large silver color rectangular one). That kind of a filter is not available in newer boards

[Edit: I fixed your quoting so your post looks right, and undeleted it. -- KrisBlueNZ]

OK that is a canned inductor .... it would be VERY RARE if one of those failed other than where it solders to the PCB ... so it begs the question ... why do you think this inductor is faulty ??

Dave

 

[Thirantha]

OK that is a canned inductor .... it would be VERY RARE if one of those failed other than where it solders to the PCB ... so it begs the question ... why do you think this inductor is faulty ??

Dave

Thank you for replying. This TV has black and white picture. No Color. I replaced all Electrolytic capacitors and pf capacitors in chroma and video sections. Checked all resistors, transistors and diodes in those areas. They are good. I also replaced the 4.43 MHz crystal. But there is no any change. Still Black and white picture. The only components I have to suspect in the chroma and video section are, Chroma IC, Video IC, Delay Line (Shown in the picture), and a Trimpot in chroma section. Do you think chroma IC causes this problem? Can tuner cause this problem? Sound is ok in this system. Therefore I did not suspect Tuner.

 

[Colin Mitchell]

I have had the delay lines go open.

 

[Thirantha]

I have had the delay lines go open.

How to check the delay line?

 

[Colin Mitchell]

It's just a coil of wire but mine went open after it warmed up and even tapping it did not detect the fault.
Just try another delay line

 

[Thirantha]

It's just a coil of wire but mine went open after it warmed up and even tapping it did not detect the fault.
Just try another delay line

That Delay Line is Z0302CE 230V. It is not available in the market. Do you know any equivalent?

 

[Colin Mitchell]

All delay lines are the same. Any delay line will work

 

[Thirantha]

All delay lines are the same. Any delay line will work

As I told you I replaced all the caps (e-caps and pf caps) in the chroma and video sections. And tested all resisters, transistors and diodes in those areas. They were all fine. I also replaced the 4.43 MHz Oscillator and the chroma chip. Color control variable resister is also good. But still the picture is Black and White. There were some trimpots in chroma and IF sections. I turn them and checked also. But No any difference. So please tell me what component cause this section. Can defective component in the power supply can cause this problem? Do I want to check IF section or Tuner? Rather than repairing this TV, I want to learn much about TV repairing. Please reply.

 

[Colin Mitchell]

I told you to replace the delay line. It can go faulty.

 

[Angelo]

I would go in order, avoiding absolutely to change components for "test" or you can increase the issues. I mean, replacing electrolytics is always a good maintenance practice in so old PS/TV's , but at this stage i would avoid replacements.

Probably you already did this, so after a good overall eye-check, i would do

1st - check power supply to arrive correctly to main IC's of the chroma ( see datasheets of the IC's and check power pins). It smells to me like a missing power.
2nd - delay line, well i never had one of that broken but you should be able to test continuity between contacts ?
3rd - things get harder, diagram at hand, and scope, starting to check color lines singnals etc