42inch Touch Screen wont power on

[epicfatigue]

Re: 42inch Touch Screen wont power on

1) Color code.

http://en.wikipedia.org/wiki/Electro...r_and_inductor

2) I think tom66 means these output diodes (circled in red). They have a marking that looks like

-><-

pin 1 is on the left, 2 in the middle, and 3 on the right. Set your multimeter to diode and test pins 1-2, 2-1 and then 2-3, 3-2.

man i got alot to learn i thought they were mospets, okay so these work late gates dont they?

What kind of results should i expect to see from each combination?

[tom66]

Re: 42inch Touch Screen wont power on

man i got alot to learn i thought they were mospets, okay so these work late gates dont they?

What kind of results should i expect to see from each combination?

Generally, for a dual package diode you expect to see:
1-2 open
2-1 ~0.2V
2-3 ~0.2V
3-2 open
3-1 open
1-3 open

It depends on the type of diode (schottky, fast recovery, and if it's a dual package); I can't see the part #s.

If any reading shows 0V, the diode is almost certainly bad.

[retiredcaps]

Re: 42inch Touch Screen wont power on

man i got alot to learn i thought they were mospets,

Don't let the physical packaging fool you. It is best to go by the pcb designator and look at the component part number and find its datasheet.

Also, it is a mosfet.

metal–oxide–semiconductor field-effect transistor

[epicfatigue]

Re: 42inch Touch Screen wont power on

Don't let the physical packaging fool you. It is best to go by the pcb designator and look at the component part number and find its datasheet.

Also, it is a mosfet.

metal–oxide–semiconductor field-effect transistor

Awesome thanks everyone once again i feel as if i am learning a lot.
I shall check all of this once i get home from work but i do have a question.

These diodes i am checking are located next to the caps that do not have power on the cold side, however we seem to be not gaining the correct voltage to the caps further back on the hot side?

Wouldn't this mean the problem is further back or are we working from one end to the other to see if anything has shorted further on from the initial problem?

(just trying to work out how we work process of elimination)

[epicfatigue]

Re: 42inch Touch Screen wont power on

They are labled D704 etc etc for all the ones listed.

thye are 3pins

1-2 = 0.162 v
1-3 = 0v
2-3 = 0.162 v

However the big white risistor labled r100JSMT mpr -5W and marking on board r601 locaded near the big cap reads .4 ohms

[retiredcaps]

Re: 42inch Touch Screen wont power on

thye are 3pins

1-2 = 0.162 v
1-3 = 0v
2-3 = 0.162 v

Retest. Look carefully at post #40 and #42 for the pin combinations.

[epicfatigue]

Re: 42inch Touch Screen wont power on

All of them read this

i started with red on pin one then reversed, should this be done the other way?

1-2 .112V (made a click)
2-1 .162V
2-3 .162V
3-2 111
3-1 0v
1-3 0v

[retiredcaps]

Re: 42inch Touch Screen wont power on

1-2 .112V (made a click)
2-1 .162V
2-3 .162V
3-2 111
3-1 0v
1-3 0v

Hmm, these readings suggest they are all bad. I would desolder one of these diodes and retest out of circuit. In-circuit readings are inconclusive since other components can be affecting the readings.

[tom66]

Re: 42inch Touch Screen wont power on

Post a picture of the diode, or read off the part number.

[retiredcaps]

Re: 42inch Touch Screen wont power on

1-2 .112V (made a click)
2-1 .162V
2-3 .162V
3-2 111
3-1 0v
1-3 0v

And just to confirm, are you measuring the diodes with the diode test function with the power off and TV unplugged?

[epicfatigue]

Re: 42inch Touch Screen wont power on

And just to confirm, are you measuring the diodes with the diode test function with the power off and TV unplugged?

yes thats correct

1-2 .195v red pin 1 black pin 2
2-1 0V black pin 1 red pin 2
2-3 0 red pin 2 black pin 3
3-2 .197 black pin 2 red pin 3
3-1 0 red pin3 black pin 1
1-3 0 red pin 1 black pin 3

->|-|<- B1861 F15JC10

[epicfatigue]

Re: 42inch Touch Screen wont power on

The above is out of circut

[retiredcaps]

Re: 42inch Touch Screen wont power on

yes thats correct

1-2 .195v red pin 1 black pin 2
2-1 0V black pin 1 red pin 2
2-3 0 red pin 2 black pin 3
3-2 .197 black pin 2 red pin 3
3-1 0 red pin3 black pin 1
1-3 0 red pin 1 black pin 3

->|-|<- B1861 F15JC10

Is it 0V or 0L? There is a huge difference between the two.

[tom66]

Re: 42inch Touch Screen wont power on

yes thats correct

1-2 .195v red pin 1 black pin 2
2-1 0V black pin 1 red pin 2
2-3 0 red pin 2 black pin 3
3-2 .197 black pin 2 red pin 3
3-1 0 red pin3 black pin 1
1-3 0 red pin 1 black pin 3

->|-|<- B1861 F15JC10

Thanks for the part number, and it's nice the manufacturer has included a marking of polarity. That indicates a diode drop should be between middle pin and each other pin, with the black terminal on the middle pin.

Let's try a test too - what reading to you get if you set your meter to diode test mode, but don't connect the probes to anything? In other words, an open circuit. I'm worried you might be confusing 0L or "1 ." for a zero.

edit: oops 1 minute too late!

[epicfatigue]

Re: 42inch Touch Screen wont power on

Thanks for the part number, and it's nice the manufacturer has included a marking of polarity. That indicates a diode drop should be between middle pin and each other pin, with the black terminal on the middle pin.

Let's try a test too - what reading to you get if you set your meter to diode test mode, but don't connect the probes to anything? In other words, an open circuit. I'm worried you might be confusing 0L or "1 ." for a zero.

edit: oops 1 minute too late!

open .0L closed 0 volts ? is that right shouldnt it read the voltage of the battery?

and yes lol it is .0L i am reading sorry guys

so this means it is functioning correctly

[tom66]

Re: 42inch Touch Screen wont power on

open .0L closed 0 volts ? is that right shouldnt it read the voltage of the battery?

and yes lol it is .0L i am reading sorry guys

so this means it is functioning correctly

Yes, those readings indicate a functional diode. Now test the other diodes. No need to post more results unless you are unsure of the reading or if you are getting odd readings. We are looking for a diode which is not behaving properly.

[epicfatigue]

Re: 42inch Touch Screen wont power on

Yes, those readings indicate a functional diode. Now test the other diodes. No need to post more results unless you are unsure of the reading or if you are getting odd readings. We are looking for a diode which is not behaving properly.

boyah lots of desoldering !!!

the white paste on these its this just thermal paste?

[tom66]

Re: 42inch Touch Screen wont power on

boyah lots of desoldering !!!

the white paste on these its this just thermal paste?

In most cases, you do not need to desolder the diodes. Remove them and test out of circuit only if you get ambiguous readings.

Yes, the white stuff is thermal paste. If you replace a diode, I recommend you add some more paste (any stuff will do, you can buy it off eBay.)

[epicfatigue]

Re: 42inch Touch Screen wont power on

kool, and is it thermal paste on these? or do i need to go out and buy something special?

Also is it possible this chip we were looking for is mounted on the small heatsink?

As it is a 6 prong i will try and get the part number off it but it is labled as an IC

[tom66]

Re: 42inch Touch Screen wont power on

kool, and is it thermal paste on these? or do i need to go out and buy something special?

Also is it possible this chip we were looking for is mounted on the small heatsink?

As it is a 6 prong i will try and get the part number off it but it is labled as an IC

The 6 pin chip might be a power supply controller; we can check it out later. For now, we'll focus on one thing at a time, the diodes for now.

Yes, the white stuff is the thermal paste. If the paste isn't smudged, then you might not need some more paste, but I'd recommend it anyway. Here is something that will work: http://www.ebay.co.uk/itm/CPU-Therma...item3f10fcf53e

Get two or three, as one of those tubes doesn't last long.