17IPS20 No LED Voltage Output

[speedypro]

Mine has no led voltage output (red circle)

Green: took out for testing, it's ok.

Image:




Yellow: Change with new off ebay, same issue.



Other two fets seems ok so never changed. Anything else to check, please?

[ReeceyBurger123]

Re: 17IPS20 No LED Voltage Output

Change the Smps controller for that mosfet if thats failed the fet wont be turned on. Its a small chip near the mosfet on the bottom side of the Pcb. Also consider testing the led mosfet and diodes for S/C just incase. That controller turns on that fet for the Led circuit I have had this issue before will be doing video soon.

[speedypro]

Re: 17IPS20 No LED Voltage Output

Hey. Where exactly? U201/U301? If you mean yellow circle: U500, done that but same.

[speedypro]

Re: 17IPS20 No LED Voltage Output

More testing, I get 115VDC on the positive pin in red: A probe on + pin and a probe (-) on the negative part of the board. When I put both probes in red circle, no voltage. So something is faulty on the negative side in red circle.

The cap beside the red circle, on the (+) pin, I get 115VDC.

[tediee]

Re: 17IPS20 No LED Voltage Output

More testing, I get 115VDC on the positive pin in red: A probe on + pin and a probe (-) on the negative part of the board. When I put both probes in red circle, no voltage. So something is faulty on the negative side in red circle.

The cap beside the red circle, on the (+) pin, I get 115VDC.

speedypro , Did you find the solution for that "minus side issue" I had the exactly the same situation with my tv, I will be very grateful if you could share the solution with me...

[Andrew F. Ali]

Re: 17IPS20 No LED Voltage Output

What are you saying...When you turn the TV with the RED probe on the +ve pin to the LEDs you have 115V wrt chassis GND and when you turn the TV with the RED probe on the -ve pin to the LEDs you have 0Vwrt chassis GND?

[tediee]

Re: 17IPS20 No LED Voltage Output

exactly, voltage measured between chassis GND and (+ve) is 115V and if you measure it between +ve and -ve on connector is 0 V.

[budm]

Re: 17IPS20 No LED Voltage Output

No Voltage reading between -Ve and GND means you have open circuit in the LED string some where.

[tediee]

Re: 17IPS20 No LED Voltage Output

hmm. I mean that I have disconnected the leds from power board connector. I measure it directly on power board pcb. So on the on the connector marked with red circle on picture (speedpro posted) on his last post.

If I measure on power board connector between +ve and -ve I got 115 V
If I measure on power board between connector +Ve and chassis GND I got 0V.

So I assume that there is sth on negative side...

[budm]

Re: 17IPS20 No LED Voltage Output

1) TV off
2) all connectors back in place.
3) Keep black probe on the chassis, red probe on the +ve then turn TV on and see how high the Voltage jumps up to, then turn TV OFF
4) Now move red probe to -VE, turn TV on and see how high the Voltage jumps up to.
5) Report those readings.

[tediee]

Re: 17IPS20 No LED Voltage Output

1) TV off
2) all connectors back in place.
3) Keep black probe on the chassis, red probe on the +ve then turn TV on and see how high the Voltage jumps up to, then turn TV OFF
4) Now move red probe to -VE, turn TV on and see how high the Voltage jumps up to.
5) Report those readings.

Results

3) black probe on the chassis, red probe on the +ve then turn TV - voltage jumps to 195V and that goes down to 115 V

4) red probe on -VE, turn TV on .
Voltage is constant on 11 V

[budm]

Re: 17IPS20 No LED Voltage Output

So the booster circuit kicks on 195V but then it goes into over Voltage shutdown so it goes back down to 115V which is the feeding Voltage to the input of the Boost converter circuits, you have open circuit in the LED string, wiring, connector problem some where.
Do you have LED tester to test the whole LED string?