42inch Touch Screen wont power on

[epicfatigue]

Re: 42inch Touch Screen wont power on

Chip looks like

L 6 5 9 (and 2x symbols that look like a light bulb and a capital D)
(84 inside a circle) 9 0 7 B 6 5 0

[retiredcaps]

Re: 42inch Touch Screen wont power on

Hmm, no luck with either part number.

What about those 2 ICs on the heatsink just above the Powerview logo? What are the part numbers of those two?

[epicfatigue]

Re: 42inch Touch Screen wont power on

I thought they were Power mosphets?

I am at work at the moment i can check when i come home be home in 2 hours.

I did notice on the far left hand side one of those atached to the heatsink is showing some discoloration and no others are.

[retiredcaps]

Re: 42inch Touch Screen wont power on

I thought they were Power mosphets?

They could be combination power mosfet and smps. I can't recall which monitor, but there was one case where the two functions were integrated into one chip.

[retiredcaps]

Re: 42inch Touch Screen wont power on

Chip looks like

L 6 5 9

May have spoke too soon about not finding the part number. Digikey has this "L6599A"

https://cdn.badcaps-static.com/pdfs/...d758189067.pdf

I'll need someone with more experience to confirm, but if it is correct part, then we are interested in measuring pin 12.

Pin 12 is the vcc. It needs between 10 and 11.4 V DC to turn on. From page 32, it looks like that should come from a 10uF capacitor. That 10uF capacitor could be the one just below the big SMPS and just to the right of the Powerview logo?

Tests
===

1) See if pin 12 (vcc) is shorted to pin 10 (gnd). Any resistance reading less than 30 ohms suggests it is bad. If yes, I believe that indicates L659 is bad.

2) Since you will have to do board acrobatics to get readings, find a piece of cardboard to rest the board on so you don't accidentally short out anything.

3) Carefully measure the DC voltage across the 10uF startup cap. Note the voltage and if it is steady of fluctuating. Black probe on negative leg and red probe on positive leg of cap.

4) Measure the DC voltage on pin 12. Be CAREFUL not to let the probe slip and short out the IC. Again, note the voltage and if it is steady of fluctuating. Use pin 10 for ground.

[epicfatigue]

Re: 42inch Touch Screen wont power on

Okay Shall do, does the Dot represent PIN 1?

Should i measure the capacitance of all the caps? or even the startup cap while we wait to confirm the part number? also what kind of voltage should i see comming off these caps?

And also can i measure the Powermosphets while in circuit?
And if so what is the correct way to test them? from memory they were a gate of some kind.

Furthermore i removed the Panel from the touchscreen unit and it is a LG panel, should i record the number for use on here? or is there no need as LG panels are used in lots of tvs.

[retiredcaps]

Re: 42inch Touch Screen wont power on

Okay Shall do, does the Dot represent PIN 1?

Generally, yes, but see datasheet to confirm pin numbering and orientation.

Should i measure the capacitance of all the caps? or even the startup cap while we wait to confirm the part number? also what kind of voltage should i see comming off these caps?

You can measure the uF if you want, but you have to desolder them to get an accurate reading. Plus I know of no multimeter that can measure ESR which is more important.

You want to see DC voltage from the startup cap.

And also can i measure the Powermosphets while in circuit?
And if so what is the correct way to test them? from memory they were a gate of some kind.

For the mosfets, I normally test for shorts. I measure pin 1-2, 1-3, and 2-3. Any reading under 30 Ohms "in circuit" suggests a possible short.

[epicfatigue]

Re: 42inch Touch Screen wont power on

Generally, yes, but see datasheet to confirm pin numbering and orientation.



You can measure the uF if you want, but you have to desolder them to get an accurate reading. Plus I know of no multimeter that can measure ESR which is more important.

You want to see DC voltage from the startup cap.



For the mosfets, I normally test for shorts. I measure pin 1-2, 1-3, and 2-3. Any reading under 30 Ohms "in circuit" suggests a possible short.

Awesome well i will measure the mosfets for shorts and check the DC voltage for the caps, gunna be fun powering up this baby and checking the voltages.

I have one question on polarized, variable and standard caps.

Stop me if i am wrong.

Polarized i just have to follow neg with positive -) |-+ (ie positibe on right neg on left ?

variable and standards i can do it either way ? or do i have to use a common ground and touch the opposite side of it.

[retiredcaps]

Re: 42inch Touch Screen wont power on

If you are measuring capacitance of the electrolytic caps, then black probe goes to negative (usually stripe on the sleeve) and red probe goes to positive.

If you are measuring DC voltage of electrolytic caps, it is the same. Namely, black probe goes to negative (usually stripe on the sleeve) and red probe goes to positive.

[epicfatigue]

Re: 42inch Touch Screen wont power on

Hey so the 4.7uf 50V cap located on Diagram as A recorded 23.7mv

Regon B all the caps recorded 0 V

Should i measure C and D voltage?

Whats my next step i feel as if i am making progress.

[retiredcaps]

Re: 42inch Touch Screen wont power on

Hey so the 4.7uf 50V cap located on Diagram as A recorded 23.7mv

If A is indeed the startup cap, that voltage is way too low.

Regon B all the caps recorded 0 V

As expected because the SMPS hasn't started.

Should i measure C and D voltage?

Whats my next step i feel as if i am making progress.

C will be 165 V DC. We know it works because we get 5 V standby. D might be the startup cap for the 5 V SMPS, but I'm not sure. It wouldn't hurt to measure it.

Also, waiting for post #25 tests 1 and 4.

[epicfatigue]

Re: 42inch Touch Screen wont power on

C= 330v
D= 120mv

and fuck me i touched the powerinvertor with my hand lmfao that shit hurts.

i shall check #25 shortly as i have to feed my dauhter

[epicfatigue]

Re: 42inch Touch Screen wont power on

Voltage moved upwards and keeptclimbing i took it of at 85mv

it has massive resitance btw

[tom66]

Re: 42inch Touch Screen wont power on

Before you look for Vcc/start up problems, check the output diodes for shorts. I was chasing around a problem like that on a DVD player (Vcc measured very low, about 1-2V) and it turned out the shorted diode on the secondary was not allowing the supply to bootstrap and supply the "run" power. If Vcc is still giving issues and diodes are not shorted, check the zener (if present), resistor and cap... Good luck.

[retiredcaps]

Re: 42inch Touch Screen wont power on

C= 330v

330 V DC means PFC is working.

and fuck me i touched the powerinvertor with my hand lmfao that shit hurts.

On the hot side, all the heatsinks are "hot".

[retiredcaps]

Re: 42inch Touch Screen wont power on

Before you look for Vcc/start up problems, check the output diodes for shorts.

Good suggestion.

[epicfatigue]

Re: 42inch Touch Screen wont power on

:O found a shorted diode should i look for anything leading to it or after it?
or just go ahead and replace it and hope she works?

[tom66]

Re: 42inch Touch Screen wont power on

I can barely see the diode you are referring to. How did you test it? Looks like that's on the primary side, as you still have standby power that is odd...

[epicfatigue]

Re: 42inch Touch Screen wont power on

I can barely see the diode you are referring to. How did you test it? Looks like that's on the primary side, as you still have standby power that is odd...

it allows current both ways, i used my diode checker on the meter.
In terms of checking resistors is there a site or a map that tells me what the bands mean so i am able to cross referance?

there is a resistor on the op side next to the chip that is red black black gold which reads 10ohms and i believe this is be a 20ohm resistor could this be the problelm? replace both the resitor and diode?

[retiredcaps]

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.