Clayton 19" LCD TV - Dead PSU

[JaYmEz]

Hello friends,

TV Brand: Clayton
TV Model:19DVDLC10M4TDT
PSU Model: 17IPS15-4 v3

The PSU had a S/C caused by the IC800 (STR W6253), it burned also the diode bridge (D800/1/2/3), radial fuse (F800) and the 0,47R resistor (R846).
I've replaced all these components and still i have no voltages on the secondary side, on the primary side there are voltages, need some guidance to know if they are right or what could be wrong.

I use this schematic:
https://www.dropbox.com/s/r4gt8ulfir...POWER.pdf?dl=0

It is for this model but not for this version, i can't find a schematic for the v3 version.
Thank you. =)

[ReeceyBurger123]

Re: Clayton 19" LCD TV - Dead PSU

Thanks for the post mate

[JaYmEz]

Re: Clayton 19" LCD TV - Dead PSU

Hello again,

I think it might be the TR801 or the optocoupler IC801, if anyone could show me the way.
Thank you.

[dick_barton]

Re: Clayton 19" LCD TV - Dead PSU

In the schematic R846 is a 56K resistor so I doubt if it's 0,47 ohms as you believe it to be.

[dick_barton]

Re: Clayton 19" LCD TV - Dead PSU

Just taken a look at the pdf and pin 2 is the source terminal of the internal mosfet so I'm wrong and it's not likely to be a 56K fitted there.

[dick_barton]

Re: Clayton 19" LCD TV - Dead PSU

You need to check your diodes around that IC and also the capacitors. The circuit will not be too dissimilar to the attachment. There should be a high voltage on D/ST (Pin1) of the IC and a lower voltage on VCC (Pin 4) but no more than 32V DC.

These readings are taken with the black meter lead to Ground (Pin5) and the red lead to make the measurements.

The readings are taken on the live side of the power supply so you need to be very careful.

[JaYmEz]

Re: Clayton 19" LCD TV - Dead PSU

Hello dick_barton,
The resistor is a 0,47 ohms i've checked by the color code, that's a diferent version of the board.
Here are the readings of the IC800 (STRW6253):

7- 320v
6- 0v
5- 10v to 12v (variable)
4- GND
3- 4v to 6v (variable)
2- Cutoff
1- 6v to 7v (variable)

Hope these readings can help.
I've checked all the diodes and they are good.
I'll check the capacitors.
Thank you.

[budm]

Re: Clayton 19" LCD TV - Dead PSU

Hello dick_barton,
The resistor is a 0,47 ohms i've checked by the color code, that's a diferent version of the board.
Here are the readings of the IC800 (STRW6253):

1- 320v
2- 0v
3- 10v to 12v (variable)
4- GND
5- 4v to 6v (variable)
6- 6v to 7v (variable)

Hope these readings can help.
I've checked all the diodes and they are good.
I'll check the capacitors.
Thank you.

I think you count the pin number wrong, pin 4 is VCC not Ground pin, as you can see pin 2 is cutoff.

[JaYmEz]

Re: Clayton 19" LCD TV - Dead PSU

You're right budm, i count them from the schematic and not from the datasheet, i'll edit the post. Thank you. =)

[dick_barton]

Re: Clayton 19" LCD TV - Dead PSU

VCC needs a minimum of 13.9V to maintain it's operation on its own if I read the data sheet correctly. I would check the capacitor and diode that is connected to the VCC (Pin 4)

[JaYmEz]

Re: Clayton 19" LCD TV - Dead PSU

Hello dick_barton,
The resistor is a 0,47 ohms i've checked by the color code, that's a diferent version of the board.
Here are the readings of the IC800 (STRW6253):

7- 320v
6- 0v
5- 10v to 12v (variable)
4- GND
3- 4v to 6v (variable)
2- Cutoff
1- 6v to 7v (variable)

Hope these readings can help.
I've checked all the diodes and they are good.
I'll check the capacitors.
Thank you.

This is the right pin count:

1- 320v
2- Cut off
3- 0v
4- 10v to 12v (variable/Vcc)
5- GND
6- 4v to 6v (variable)
7- 6v to 7v (variable)

dick_barton I've checked those components and they are good, in other hand i found in the vcc circuit that in place o R898 there is a jumper and in the R575 there is a 10 ohms resistor. By the schematic there should be two 15 ohms resistors. I'm going to post some photos of the primary circuit later today.
Thank you! =)

[JaYmEz]

Re: Clayton 19" LCD TV - Dead PSU

Here are two photos of the primary circuit:

-Top photo:
https://www.dropbox.com/s/f55bjhzlid...y_top.jpg?dl=0

-Bottom photo:
https://www.dropbox.com/s/ldtj85lv4g...ottom.jpg?dl=0

Now you can see the differences between the schematic and the real board.

[dick_barton]

Re: Clayton 19" LCD TV - Dead PSU

What's the voltage between pins 3 & 4 of the optocouler IC801. It's on the live side so you measure with care.
The photo's are better added as an attachment to your thread so that they are there for others to see at a later date.

[JaYmEz]

Re: Clayton 19" LCD TV - Dead PSU

I attached the photos to this post.
The voltage between pins 3 and 4 of the IC801 is 5v.

[dick_barton]

Re: Clayton 19" LCD TV - Dead PSU

Thanks,
What ac voltage do you have on TR801 Pin 6 (VC). Trying to establish why VCC to the STR chip is low.

[JaYmEz]

Re: Clayton 19" LCD TV - Dead PSU

On pin 6 of the TR801 the one connected to R898 (by the schematic) i have 0v AC or DC there is no voltage on that pin, this could be the reason.
Between pin 6 and pin 5 of TR801 i have 0,55 ohms

Thank you!

[dick_barton]

Re: Clayton 19" LCD TV - Dead PSU

Check D804 for short circuit which is a 22V zener diode. Being a 22V zener I would expect the voltage across it to be close to but not exceeding 22V DC.

[Diah]

Re: Clayton 19" LCD TV - Dead PSU

I attached the photos to this post.
The voltage between pins 3 and 4 of the IC801 is 5v.

yours PSU missing one SMD Diode D824

[JaYmEz]

Re: Clayton 19" LCD TV - Dead PSU

dick_barton I've checked D804 and it's good but it's not a 22v zener diode, the marking is WP, which stands for BZT52C27 a 27v 500 mW zener diode. Another thing, C807 it's not a 22uF 50v electrolytic capacitor the one onboard is a 33uF 50v. They've changed some components in this revision.

Diah That must be like that, some of the components onboard don't match the ones on the schematic.

Thank you! =)

[dick_barton]

Re: Clayton 19" LCD TV - Dead PSU

What ac volatge do you have across pins 2 & 4 of TR801. Meter probes connected to both pins of the transformer.