Vestel 17IPS62 power supply dead by lighting

[Trofazni]

Hi guys, i have a problem with this power supply, that did not survive lightning.

Find out that transistor that regulates optocoupler on secondary side was faulty, replaced it and checked components around it, now it seems ok, but there were no sucess. So i look further, and on primary side fet that drives transformator and his controler were dead (smps). I have replaced them. Checked other components, everything seems ok, and I have a progres, but not in full. It is trying to start but no sucess. There are no shorts anywhere, but it does not work.
I tried feeding 12v line with external 5v, and optocoupler switches on primary smps controller (U1 FAN6300), but his cappacitor charges and discharges, has no steady voltage...Look at the video, unimer is measuring smps cappacitor, and osciloscope is on secondary side 12v line that goes on optocoupler, without external voltage feed, as it should be.
Where should i look now? This power supply is too simple, but it is making me problems...

https://www.youtube.com/watch?v=_rQAC2Jy-eg

[petehall347]

Re: Vestel 17IPS62 power supply dead by lighting

check diodes for short

[Trofazni]

Re: Vestel 17IPS62 power supply dead by lighting

Every diode is ok, nothing is shorted.. I checked that, caps, diodes, fuses, resistors...

[R_J]

Re: Vestel 17IPS62 power supply dead by lighting

Was the primary fet shorted? if it was, R60-R63 might be open. do you have voltage on pin8 of U1?

[Trofazni]

Re: Vestel 17IPS62 power supply dead by lighting

Yes, i wrote that Primary fet and controller were shorted gate to drain. I have replaced them, then it came back to life, but only to trying to start, which is progress, no?
No ressistors are open, i measured all of them...

The difference between my pcb and schematics that 3 resistor series that are marked R64, 65, 66 in psu are 3x39K total in ~120kOhm, but in schematics are ~30R. On pin +400V in schematics there is standard ~310V, then three series resistors and to pin 8 of IC. Voltage drop is happening in those three resistors, steady voltage before resistors, fluctuating on pin 8, and I do not know why. And why is on pcb 120kohm, on pdf 30R?

[Trofazni]

Re: Vestel 17IPS62 power supply dead by lighting

https://www.youtube.com/watch?v=y_q_3oRd7Rk
This is voltage across IC ground and HV pin 8.

[petehall347]

Re: Vestel 17IPS62 power supply dead by lighting

did you change the controller chip yet ?
also check c75

[dick_barton]

Re: Vestel 17IPS62 power supply dead by lighting

Yes, i wrote that Primary fet and controller were shorted gate to drain. I have replaced them, then it came back to life, but only to trying to start

Did you check D26 since if you had a Drain to Gate short 300+V would have been across the zener.

[Trofazni]

Re: Vestel 17IPS62 power supply dead by lighting

did you change the controller chip yet ?
also check c75

Yes I changed it with the fet togeather.
C75 is 26pF according to tester. On schematics is 10pF, so I assume that is ok.

Did you check D26 since if you had a Drain to Gate short 300+V would have been across the zener.

I do not have D26 on PCB its d36 across electrolytic cap? Anyway i checked it, voltge drop is 0.56V.

And let me correct myself, drain to gate is 277kOhm, drain to source 160k, but gate to source is 385 Ohm.
Also, on IC controller FAN 6300A, it's gate was short to it's gate, 8 Ohm.


Anyone can explain what I asked about "The difference between my pcb and schematics that 3 resistor series that are marked R64, 65, 66 in psu are 3x39K total in ~120kOhm, but in schematics are ~30R. On pin +400V in schematics there is standard ~310V, then three series resistors and to pin 8 of IC. Voltage drop is happening in those three resistors, steady voltage before resistors, fluctuating on pin 8, and I do not know why. And why is on pcb 120kohm, on pdf 30R?"

[R_J]

Re: Vestel 17IPS62 power supply dead by lighting

You could have a bad D29 zener on the output of the optocoupler, I think the FB line should be higher than the 5mv you measured, should be more like 2-3 volts
Or the optocoupler could be bad

[Trofazni]

Re: Vestel 17IPS62 power supply dead by lighting

You could have a bad D29 zener on the output of the optocoupler, I think the FB line should be higher than the 5mv you measured, should be more like 2-3 volts
Or the optocoupler could be bad

Changed it with 18V one, same thing happening. Optocoupler has 0.135 voltage drop across pins 3 and 4 when 1.2V is applied to pins 1 and 2, so I guess everything is ok, but it is not working

[dick_barton]

Re: Vestel 17IPS62 power supply dead by lighting

I wouldn't worry about the resistors R64, R65 & R66 being marked 10 ohms on the schematic. Whatever value is given on them, check with your meter that they read what it says otherwise change them.

The FAN6300 requires a minimum voltage on C37 of 16V to run continuously and will stop if the the voltage falls to 10V or less.

In your post above it shows 15V so I suspect the FAN6300 is continuously attempting to power up.

So make certain that the 3 resistors match the value given on them and I would also consider changing C37

It is of course possible that you may have a fault on the secondary side of the power supply which would also shut the FAN6300 down.

[Trofazni]

Re: Vestel 17IPS62 power supply dead by lighting

I wouldn't worry about the resistors R64, R65 & R66 being marked 10 ohms on the schematic. Whatever value is given on them, check with your meter that they read what it says otherwise change them.

They are ok, all 3 of them are 39K, as are markings on them.

In your post above it shows 15V so I suspect the FAN6300 is continuously attempting to power up.

Yes, you are correct.

I would also consider changing C37

Measured it with esr meter, also tried to replace. Same thing, it's good cap.

It is of course possible that you may have a fault on the secondary side of the power supply which would also shut the FAN6300 down.

Well, as you mentioned that, there was fault on secondary side, but i solved it before aknowleging that the primary side if faulty, too.
Transistor Q5 that drives optocoupler was damaged, so i replaced it with another npn small signal transistor. Also checked resistors around him, one faulty, replaced. OC feed is ok, pulsing with primary between 0.8-1.2V, as its trying to power on. So i assume that fault on sec side is eliminated.

I also tried to unhook coil L4, to separate transformer from the rest of 12V line on secondary side, as I am feedeng it (seconday side components, but not transformer) with 5V from external power supply. In that external 5V feed conditions, i have steady 1.2V on optocoupler, and 0.13V voltage drop on pins 3 and 4 on primary side, so i assume that optocoupler circuit, and secondary 12V line are working correctly, as there are no shorts, heat, or anything.
When psu secondary is fed externally, and when i plug it in mains, primary side is doing the same thing... trying to start.
If fault is in secondary, this feedeng should turn on psu normally, since secondary side of transformer is dissconected from 12mains..

Am I getting it right, or am I totally off track? Is this the way I can test this, or am I getting sometnihg wrong?

[dick_barton]

Re: Vestel 17IPS62 power supply dead by lighting

What did you replace the transistor with? part number

Did you check Q13, Q3 & Q1 if fitted and also D21.

[Trofazni]

Re: Vestel 17IPS62 power supply dead by lighting

What did you replace the transistor with? part number

6cw02 is marking on it, it should be BC817
https://cdn.badcaps-static.com/pdfs/...3c43bf696b.pdf

What voltage do you have even if briefly on the 12V, 24V and Vled when you switch on.

Screenshots of voltages are uploaded...

[dick_barton]

Re: Vestel 17IPS62 power supply dead by lighting

Check the diodes with your meter in diode mode and set switch off and also the resistance from each of the X points to chassis.

[Trofazni]

Re: Vestel 17IPS62 power supply dead by lighting

What do you mean and set switch off? I don't understand.

Diodes are measured when removed from the pcb.
D9-0.231mV
D7-0.236mV
D8-0.224mV

D23-0.419mV
D24-0.433mV
D25-0.405mV

To chasis:

X L4 - ~30k
X 24V - 1.7M
X 24V_AC - 1R

[dick_barton]

Re: Vestel 17IPS62 power supply dead by lighting

Those readings appear fine. Did you change the FAN IC?

[Trofazni]

Re: Vestel 17IPS62 power supply dead by lighting

Those readings appear fine. Did you change the FAN IC?

Driver for fet on primary side? Yes, it's gate was shorted to ground... I litteraly do not have any ideas...

[R_J]

Re: Vestel 17IPS62 power supply dead by lighting

You say you replaced Q5, Is U3 ok? Do you get any voltage at all on the secondary, even a couple volts on +12?
I still think your optocoupler is defective