17IPS20 No Led Voltage Solved With Video :)

[johnboy183]

Re: 17IPS20 No Led Voltage Solved With Video

Well as promised spent an extensive day of checking and testing using your suggestions.
First with all components in and no power on I checked the following readings:
on 200 ohm scale:
Pin 13 to ground = 11.4 ohms
R522 to ground = 11.4 ohms
C519 + to ground = 11.4 ohms
C 519 - to ground = 0.2 ohms
R522 out to ground = 0.4 ohms.
R522 disconnected from Pin 13 trace then Pin 13 to ground reads 1
C519 removed and tested on 2M scale reads 6.6 continually rising.
With R522 and C519 removed Pin 13 to ground reads 1 on all meter resistance scales
With R522 and C519 removed Pin 13 to Pin 4 reads 1 on all meter resistance scales C519 reinstalled then Pin 13 to ground reads 1 on 200- 2M scales
R522 reinstalled as well then Pin 13 to ground reads 11.4 ohms (Obviously the resistors value of 11 ohms)

From all of the above and rechecking all solder joints I felt I could move to live testing (hopefully).
With LEDs left disconnected I powered up the boards. No obvious shorts or bangs and no magic smoke but also still no 156-160 voltage either.

Following readings then taken:
On Standby Vin = 16.4 volts
On Standby Vcc = 0 volts
Power on Vin = 10.8 volts
Power on Vcc = 5.0 volts

Voltages measured at main board connector:
12 volt shows 16.4 volts
24 volt shows 33 volts
3.2 volts shows 2.2 volts now
So still something not functioning correctly - any suggestions as I am now out of ideas and readings?

[budm]

Re: 17IPS20 No Led Voltage Solved With Video

Well as promised spent an extensive day of checking and testing using your suggestions.
First with all components in and no power on I checked the following readings:
on 200 ohm scale:
Pin 13 to ground = 11.4 ohms
R522 to ground = 11.4 ohms
C519 + to ground = 11.4 ohms
C 519 - to ground = 0.2 ohms
R522 out to ground = 0.4 ohms.
R522 disconnected from Pin 13 trace then Pin 13 to ground reads 1
C519 removed and tested on 2M scale reads 6.6 continually rising.
With R522 and C519 removed Pin 13 to ground reads 1 on all meter resistance scales
With R522 and C519 removed Pin 13 to Pin 4 reads 1 on all meter resistance scales C519 reinstalled then Pin 13 to ground reads 1 on 200- 2M scales
R522 reinstalled as well then Pin 13 to ground reads 11.4 ohms (Obviously the resistors value of 11 ohms)

From all of the above and rechecking all solder joints I felt I could move to live testing (hopefully).
With LEDs left disconnected I powered up the boards. No obvious shorts or bangs and no magic smoke but also still no 156-160 voltage either.

Following readings then taken:
On Standby Vin = 16.4 volts
On Standby Vcc = 0 volts
Power on Vin = 10.8 volts
Power on Vcc = 5.0 volts

Voltages measured at main board connector:
12 volt shows 16.4 volts
24 volt shows 33 volts
3.2 volts shows 2.2 volts now
So still something not functioning correctly - any suggestions as I am now out of ideas and readings?

The Voltage readings do not make sense to me.
1) Look at the relationship between Vin in standby, you have 16.4V, then when TV is turned on the Vin drops down to 10.8V, but the 12V at the main board shows 16.4V, this is not right because that 12V of the power supply board connector CN3 pin 11 & 12 are for 12V, this same 12V is fed to the MOSFET switch Q214 to supply the 12v to Vin pin 15 of IC U500, so it is not right to have 10.8V at Vin but have 16.4V on the 12V pin at the power supply connector, it should show the same reading unless Q214 is bad.

2) You need to check your meter or the way you measure the 12V and the 24V which they show as way too high, and the 3.2V is showing way too low.

[johnboy183]

Re: 17IPS20 No Led Voltage Solved With Video

Just another glitch with this whole project -- battery was dying in MDM I now find ( presumably as it had been on for a long time during the day of testing plus the battery in it was a rechargeable which I dont normally use as they seem to sudden death but only one I had ).
Checked as many of the measurements I gave you yesterday as I could and they all were the same except for the main discrepant voltage readings:
Voltages measured at Main board connector:
12 volt shows 11.9 volt consistently now
24 volt shows 24.0 volts consistently
3.2 volt shows 3.2 volts consistently

However:
On standby Vin = 11.9v
On standby Vcc = 0 v

Powering up Vin starts at 11.9v for maybe 20 secs then goes to 7.67v
Powering up Vcc starts at 0v for maybe 20 secs then goes to 0.19v- 0.28v

tracking along the trace from Vcc pin to where it reaches S505 the voltage remains as 7.67v as long as board switched on.
On the other pole of S505 the voltage remains at 11.9v whether on or in standby. S505 also has a second trace from its high volt side to further down the board and that remains at 11.9 v consistently.
switch the set back into standby and all of these 7.67 v points all return to 11.9v
Mosfet Q511 follows the same pattern with all 3 pins showing either 7.67v or 11.9v on standby or on. All 3 pins showing the same voltage doesn't seem right to me.
Does all of the above point to any further culprits or blown components.

[budm]

Re: 17IPS20 No Led Voltage Solved With Video

Just another glitch with this whole project -- battery was dying in MDM I now find ( presumably as it had been on for a long time during the day of testing plus the battery in it was a rechargeable which I dont normally use as they seem to sudden death but only one I had ).
Checked as many of the measurements I gave you yesterday as I could and they all were the same except for the main discrepant voltage readings:
Voltages measured at Main board connector:
12 volt shows 11.9 volt consistently now
24 volt shows 24.0 volts consistently
3.2 volt shows 3.2 volts consistently

However:
On standby Vin = 11.9v
On standby Vcc = 0 v

Powering up Vin starts at 11.9v for maybe 20 secs then goes to 7.67v
Powering up Vcc starts at 0v for maybe 20 secs then goes to 0.19v- 0.28v

tracking along the trace from Vcc pin to where it reaches S505 the voltage remains as 7.67v as long as board switched on.
On the other pole of S505 the voltage remains at 11.9v whether on or in standby. S505 also has a second trace from its high volt side to further down the board and that remains at 11.9 v consistently.
switch the set back into standby and all of these 7.67 v points all return to 11.9v
Mosfet Q511 follows the same pattern with all 3 pins showing either 7.67v or 11.9v on standby or on. All 3 pins showing the same voltage doesn't seem right to me.
Does all of the above point to any further culprits or blown components.

1) When the meter battery is low, the readout will show higher Voltage reading.
2) On standby Vin = 11.9v
On standby Vcc = 0 v

Powering up Vin starts at 11.9v for maybe 20 secs then goes to 7.67v
Powering up Vcc starts at 0v for maybe 20 secs then goes to 0.19v- 0.28v.

I read the spec sheet again, even though the block diagram shows it as plain 6V LDO, it is not, it is switched LDO, meaning the EN pin has to be activated to turn on this LDO that is why in standby you do not have 6V at VCC until you turn on the TV.
For the Vin to drop to 7.67V, but 12V power supply still shows 11.9V as you report, it may mean that the switched 12V MOSFET Q214 for the 12VCC_SW that feeds Vin of U500 may be not working properly or the IC is loading down too much, so check the Voltage on Source pin and Drain pin Gate pin of Q214 when in standby and when TV is on.
It also does not make sense that now you have only VCC of only 0.19 ~ 0.28V when in post 81 you have this:
Power on Vin = 10.8 volts
Power on Vcc = 5.0 volts
Something changes.

[johnboy183]

Re: 17IPS20 No Led Voltage Solved With Video

"Power on Vin = 10.8 volts
Power on Vcc = 5.0 volts"
I cant answer this other than I wonder if the low MDM battery was starting to kick in then skewing the readings.
Will try what you suggest tomorrow.
Is having 11.9v or 7.6v on all 3 pins of Q511 normal behaviour?
Also have you any comment on why S505 can have 11.9v on one pole and 7.6v on the other pole if its simply a resistor - or is its purpose to act as a safety?
Also the Q214 datasheet I can find does not clearly identify the Source, Gate and Drain pins out of the 8 pins. Do you have any better info on this?

[budm]

Re: 17IPS20 No Led Voltage Solved With Video

"Power on Vin = 10.8 volts
Power on Vcc = 5.0 volts"
I cant answer this other than I wonder if the low MDM battery was starting to kick in then skewing the readings.
Will try what you suggest tomorrow.
Is having 11.9v or 7.6v on all 3 pins of Q511 normal behaviour?
Also have you any comment on why S505 can have 11.9v on one pole and 7.6v on the other pole if its simply a resistor - or is its purpose to act as a safety?
Also the Q214 datasheet I can find does not clearly identify the Source, Gate and Drain pins out of the 8 pins. Do you have any better info on this?

1) Q511 is used as a switch it is part of the LED current path,if it is bad you will not have backlights when all other circuits are working, it is not doing anything right now because U500 is not running.

2) Part designator with Sxxx and Jxxx should be just jumper wire, as I indicated before, the schematic is the master schematic for making PCB so all the parts are shown in the schematic. In this case if R513 is not installed the jumper S505 will have to be installed for the IC to get Vin, if R513 is installed then S505 will not be installed. If we have the BOM of the this board assembly that you have then it will be so much less confusion as to what parts are being used and not used. Since S505 is just jumper wire connected between +12VCC_SW and Vin pin 15 OF U500 so I cannot see how it can have 11.9V on one end and 7.6V on the other end, it has to be real bad connections to have that much Voltage drops on a piece of jumper wire.
May be show me the pictures of this S505.
See picture of Sxxx jumper attached.

3) Q214 pinout, as shown in the schematic, pin 1,2,3 are Drain, pin 4 is Gate, pin 5, 6, 7, 8 are Source. You do know where pin 1 is on the Q214, right?

4) Q214 and jumper S505 are present on you board, correct?

[johnboy183]

Re: 17IPS20 No Led Voltage Solved With Video

1) Well aware Q511 as a mosfet is a switch - why does it have have 11.9v on all three pins?
2) As I indicated above that I measured both sides of S505 (it is a resistor marked 101) I'm not sure why you are asking if its present? If its simply a jumper why can it have 11.9 volts on one pole and 7.67v on the other? I need to understand its function.
3) Yes i know which would be pin 1
4) As said above S505 is on board. Have just been out to the workshop to look at board and cant find any 8 pin IC marked on board as Q214. I cant even find the board marking for Q214 but it is 1 am here so will look in daylight but even if I find the pads for it there does not appear to be such a chip mounted.

[budm]

Re: 17IPS20 No Led Voltage Solved With Video

1) Well aware Q511 as a mosfet is a switch - why does it have have 11.9v on all three pins?
2) As I indicated above that I measured both sides of S505 (it is a resistor marked 101) I'm not sure why you are asking if its present? If its simply a jumper why can it have 11.9 volts on one pole and 7.67v on the other? I need to understand its function.
3) Yes i know which would be pin 1
4) As said above S505 is on board. Have just been out to the workshop to look at board and cant find any 8 pin IC marked on board as Q214. I cant even find the board marking for Q214 but it is 1 am here so will look in daylight but even if I find the pads for it there does not appear to be such a chip mounted.

1) The Drain is connected to the Cathode of the LED string which is fed by Voltage source and you also have body diode of the MOSFET that is back fed through resistor between Gate and Source through body diode, the Gate is fed by the 12VCC_SW, Gate and Source pin has resistor connected and since the IC U500 is not running then the Voltage at the Source pin will be same at the GATE due to R563.

2) I asked if S505 is present or not since we do not know what your board version is stuffed with which parts, and as I show you in the last picture, the parts with Sxxx are just plain jumper wire that is why I ask for picture, So can I see what S505 look like? If it is resistor then it will have Voltage drops on that 100 Ohms resistor, in this case 11.9V - 7.67V = 4.23V which means the current flow of 42.3mA, that is lots of current when the IC is not even running, if you look at page 3 of the spec sheet of U500, the quiescent current at 12V is around 4mA, so 42mA is not normal at all, the problem is around that IC and associated parts around that IC.

3) "Yes i know which would be pin 1" So if you know what pin 1 one is then you know what all the pins are then as shown in the schematic and as I explain as to which pin is what.

4) If the Q214 is not installed then the +12VCC_SW is not used, that is why it will be lots of work to find out what are actually used and not used on your board. At this point you will have to look at your board and mark the schematic as to what are install and not installed, and what the values are, otherwise will be spending lots of time troubleshooting due to schematic and the board assembly mismatch. We did know that U500 was bad since you were able to get the backlights to come on, but now we are trying to find out what get damaged due to your mishap.

[johnboy183]

Re: 17IPS20 No Led Voltage Solved With Video

Here is a photo of S505 on the board unless I am misreading the board marking

[johnboy183]

Re: 17IPS20 No Led Voltage Solved With Video

Finally found location of Q214 position and as you can see it is absent

[johnboy183]

Re: 17IPS20 No Led Voltage Solved With Video

You say above "the problem is around that IC and associated parts around that IC." Which "IC" do you mean in this comment so I can concentrate on that?

[budm]

Re: 17IPS20 No Led Voltage Solved With Video

You say above "the problem is around that IC and associated parts around that IC." Which "IC" do you mean in this comment so I can concentrate on that?

1) IC U500, the LED driver IC.

2) So Q214 is not installed, that means S522/S529 are installed to bypass Source and Drain pins of Q214, please check to see if that is true or not.

3) Is one end of S505 connected directly to pin 15 Vin of U500? And another end of S505 is connected to S522/S529/Q214 Soucre solder pad? Please check.

VESTEL board is one of the worst board to work with due to so many variation and also due to not having the schematic that exactly matched the PCB assembly. This is very frustrating to troubleshoot.

[johnboy183]

Re: 17IPS20 No Led Voltage Solved With Video

S522 is there and close to it is S526. S529 is also there.
Yes - one end of S505 goes directly to Pin 15 Vin. The other end connects directly to S522/S529 /Q214 solder pad.
Working on the board today I began to suspect Mosfet Q502 (FQD7N30) and have removed from the circuit. It tests faulty.
On diode setting with red on Source + black on Drain = 0.158. Reverse the leads reading = 0.157. Gate to Drain with red on drain= 0.326 and the same reading if probes reversed. Gate to Source red and black in both directions = 0.209.
I assume this is another casualty of the accidental short but could it account for the Vin dropping from 11.9 v to 7+ volts on startup do you think?

[budm]

Re: 17IPS20 No Led Voltage Solved With Video

Q502 N-CH MOSFTE for the LED boost converter.
The Gate pin is isolated from Source and Drain so the readings between Gate and Source, Gate and Drain should show as open circuit.

The Source and Drain should show as diode due to the body diode of the MOSFET.
Since you have reading between Gate and Drain, that means the Drain Voltage is dump into the Gate drive output of U500 and that will damage the U500 Gate drive output since the Gate drive output cannot take high Voltage dump from the Drain pin.
U500 looks to be damaged at this point since it is drawing so much current through the 100 Ohm S505.
It still does not make sense why they use S505 100 Ohms resistor to feed the Vin OF U505, the more the IC draws current the less Vin Voltage will be for the IC to run.

[johnboy183]

Re: 17IPS20 No Led Voltage Solved With Video

I need to fully understand what you are saying here, and I don't unfortunately.
1)Are you agreeing that Q502 is dead and requires replacement?
2) Are you saying that the second fitted new U500 is now damaged and that is because up to 12 volts has been coming through it via the mosfet drain? (since the new U500 was fitted there has been no voltage larger than 11.8 volts recorded on the mosfet GD or S or any other component in this part of the board)
3) Or are you meaning that U500 is damaged as a result of the 42.3mA coming via S505 due to the difference between the 11.9v and 7.67v at S505 junction?

4) or both 2 and 3?

5) The trace from S505 also interacts with Q511 via R561 so will that have any bearing on the situation?

6) I still have no understanding of how at U500 Pin 2 Vin is 11.9v at standby, and at the commencement of power up, only for some 20 secs later it to drop to 7.67v! what could cause that to happen?

Unfortunately I cant just keep refitting new U500s every time the set is switched on as the pads at that point are now almost non existent so what would you advise my next actions to be?
( I have ordered a new FQD7N30 but would have to re-order a new MP3394S if needed and hope I can successfully fit it)

[johnboy183]

Re: 17IPS20 No Led Voltage Solved With Video

An update on earlier:
In 6) I incorrectly typed Pin 2 instead of Pin 15 so ignore that typo.
Have powered up the board with FQD7N30 left out of circuit and now its Drain and the LED connector + pin again read 156v
Have disconnected the trace from S505 along its path to Pin 15 at various points ( via jumper pins and joints) testing up to each disconnection and right up to Pin 15 ( if Pin 15 is disconnected from its pad) it retains 11.9 volts at every point along the way until Pin 15 and its pad are reconnected when it immediately drops to 7.6 volts. So it would appear as you feared than U500 or one of its other pins is the source of the voltage drop. Any thoughts on this later news?

[johnboy183]

Re: 17IPS20 No Led Voltage Solved With Video

Just a follow up on above. As the accidental short happened BEFORE this latest U500 was fitted there has to be an external reason it has now faulted. Do you think the shorted mosfet could have been the culprit as I have yet to find any other failed component so far?

[budm]

Re: 17IPS20 No Led Voltage Solved With Video

1) Q502 is bad.
2) Q502 Drain is fed by 24 -80V power source as shown in the schematic, but it is actually 150V which is then boosted up to 190V or so if U500 and Q502 are working so when you have short between Drain and Gate, the Voltage is dumped into the Gate drive output of U500.

3) "Have powered up the board with FQD7N30 left out of circuit and now its Drain and the LED connector + pin again read 156V" Which Q is that FQD7N30? Q502?

[johnboy183]

Re: 17IPS20 No Led Voltage Solved With Video

Yes - FQD7N30 is Q502
Do I take it from what you are saying that the shorted Q502 has therefore damaged the latest U500 and the only solution is yet another new U500?
If I replace Q502 and U500 do you think its reasonable to expect the board may now function without damaging the U500?
Thanks again

[budm]

Re: 17IPS20 No Led Voltage Solved With Video

Yes - FQD7N30 is Q502
Do I take it from what you are saying that the shorted Q502 has therefore damaged the latest U500 and the only solution is yet another new U500?
If I replace Q502 and U500 do you think its reasonable to expect the board may now function without damaging the U500?
Thanks again

Replace all the suspected bad parts is all we can do at this point.
U500 was damaged by bad Q502, so make sure Q502 is tested good and caution must be made when handling MOSFET and IC, they can be damaged by electrostatic discharge.
https://toshiba.semicon-storage.com/...t-mosfets.html
https://cdn.badcaps-static.com/pdfs/...25f188d2be.pdf