Dead Vestel 17IPS71 power board

[FullnameJon]

Re: Dead Vestel 17IPS71 power board

Forgot to say that it made no difference if I heated those capacitors up. Still resets.

[FullnameJon]

Re: Dead Vestel 17IPS71 power board

Ok, I can't even find the marking for C295. C302 isn't populated. C296 read 95.76uF and 0.40ohm.
C64 110nF no ESR reading.
C73/C33 (double marking, same spot) is a 100uF 35V that read 105.2uF 0.34ohm.

[FullnameJon]

Re: Dead Vestel 17IPS71 power board

I have checked those. I will check the caps as soon as I can.

[budm]

Re: Dead Vestel 17IPS71 power board

OK, try to locate the lytics caps as shown in the solid red boxes I marked, then heat them up with hair dry for few minutes then power up the board by itself to see if the Voltage will become stable or not.
BTW, you did check all the power diodes in the cold side correct since I see some of the legs had to be soldered back in place, correct?

[FullnameJon]

Re: Dead Vestel 17IPS71 power board

Yes sir

[budm]

Re: Dead Vestel 17IPS71 power board

If I test the DC output with the mainboard connected, the voltages drop even faster than before. Measured HV from FAN6300A to 320V and VDD peaks at 20.68V but dies almost directly then goes back up and repeats.

Are you still getting unstable output if main board is not connected?

[FullnameJon]

Re: Dead Vestel 17IPS71 power board

I've tested another mosfet and optocoupler, no difference. U202 or something before it keeps resetting it seems.

[budm]

Re: Dead Vestel 17IPS71 power board

I did not read the latest thread in details yet to see what is going on with FullnameJon's board.
Can we see good clear straight shots of the whole bottom side of your board?
I also attach the Vestel training manual for 17IPS71 for reference.

[FullnameJon]

Re: Dead Vestel 17IPS71 power board

If I test the DC output with the mainboard connected, the voltages drop even faster than before. Measured HV from FAN6300A to 320V and VDD peaks at 20.68V but dies almost directly then goes back up and repeats.

[dick_barton]

Re: Dead Vestel 17IPS71 power board

Disconnect the mainboard from the power supply and power up. Check if Pin 9 of CN4 = 5V. If not then this voltage comes from the mainboard and is fed back to the power supply.

[FullnameJon]

Re: Dead Vestel 17IPS71 power board

I noticed that too but they're connected. Didn't bother tidying it up yet.

Pin 9 shows 1.5V. Where does that come from? There's no Q1.

[dick_barton]

Re: Dead Vestel 17IPS71 power board

It looks like the diodes have had their legs cut to check them but D13 and D15 look as though they are not soldered back in place correctly.

You have missed some of the voltages on the connector

[FullnameJon]

Re: Dead Vestel 17IPS71 power board

1 - 24V
4 - 2.5V
10, 11, 12 - 12V

Again, it moves around a bit as the supply restarts.

[dick_barton]

Re: Dead Vestel 17IPS71 power board

FAN6300A was what I meant but ignore for now.

Can you post a photo of your board.

Can you also give the voltages you have on each of the pins of connector CN3 or CN4 whichever one is fitted to your board.

[FullnameJon]

Re: Dead Vestel 17IPS71 power board

Board is R4.

Pins 1-8 where?

C19 is 320-321V

[dick_barton]

Re: Dead Vestel 17IPS71 power board

What version is your board r2, r3 etc???

What voltage do you have on the pins 1 - 8. Use the negative leg of C19 as the ground for your meter. Be carefull since there is high voltage on this part of the circuit so measure with a steady hand.

What voltage do you have between the two pins of C19. Should be close to 400V and steady

[FullnameJon]

Re: Dead Vestel 17IPS71 power board

I've gone through this thread a couple of times but my issue doesn't seem to match, I think. I get 12 and 24V outputs, but not stable. I can hear something restarting every couple of seconds and the voltages on the DC side drop just a little bit before it goes up again, and then down a bit. No standby light and no life in the TV other than the unstable voltages. I've replaced FAN6300A as I thought that was causing the issue, but no luck. Bad caps? Bad IC?

[budm]

Re: Dead Vestel 17IPS71 power board

Yep, that schematic, 17ips71-r3, from post #17 is not from Vestel, it looks like it was drawn by some one else with lots of wrong value parts, I.E. lots of resistors are marked as '10R', and connections.

[R_J]

Re: Dead Vestel 17IPS71 power board

That 17ips71-r3 schematic with R294 is drawn WRONG. R294 cannot be connected that way, if it was the ic would get aprox 390vdc on the VDD pin and the ic would get blown off the board.
The 17ips71-r4 schematic in post 149 would be correct.

[JonathanAnon]

Re: Dead Vestel 17IPS71 power board

[QUOTE=dick_barton;968967]When the voltage on the capacitor reaches a set point (data sheet) then the internal circuit switches off and allows feedback from the transformer (N3 winding) to maintain that voltage.[quote]

Is this common now? I haven't seen that before on any of the other TVs I've worked on. I guess I will know to look out for it now.

It is also worth checking D20 is not short circuit.

Yeah I checked it it's good. One bad diode on the secondary side but I got that sorted.

Do you have any voltage at the VDD pin. Don't forget to use the HOT ground and not chassis to measure the voltage.

Yeah I always use the main filter cap ground as the ground for primary side measurements.

17ips71-r4.pdf
All I could find was the R3 version of this schema, which was what I was working from, but that seems like a more accurate reflection of what I'm looking at. Boy, I wish I'd had that a few days ago! Just ordered the PWM chip, thanks Dick.