VESTEL 17IPS61-3 shorted output diodes

[dick_barton]

Re: VESTEL 17IPS61-3 shorted output diodes

Something is not adding up.

The readings are very strange, here they are:

3 -0.02V
5 0.00V
7 0.06V
9 0.00V
11/13/14 11.18V
15 0.00V

However in post #54 you say

12V between 13/14 and 2
5V between 9 and 2
24V between 15 and 2

[John843883]

Re: VESTEL 17IPS61-3 shorted output diodes

Hello to everyone and first of all please excuse me for not coming back before.
First of all, here are the actual photos for my PSU:







the third one being a detail of a thermistor with a black mark on it: it doesn't seem a burning sign though, just some kind of glue.
The readings are very strange, here they are:

3 -0.02V
5 0.00V
7 0.06V
9 0.00V
11/13/14 11.18V
15 0.00V

I know that according to the schematics for the board I'm supposed not to be getting any voltage reading on pin 11 but I've double checked. Also, pin 11 isn't NC as in the schematics but connected to a resistor.
Another difference is that pin 14 and 18 are bridged.
For what concernes the screws, yes I had noticed they were somewhat loose.

Can you check to see if the missing voltages are present at their points of origin (across their respective filter caps)?

Also I found a schematic here http://mharding.net/wp-content/uploa...1-3-VESTEL.pdf

Its acting like some of the fuses, jumpers or 0 ohm resistors are open especially since the 12v and 24v rail are from the same transformer so something should be there.

Are the readings with missing voltages taken with the other board or back-light LEDs connected?

[guybrushthreepwood]

Re: VESTEL 17IPS61-3 shorted output diodes

@dick_barton

I apologize for the misunderstanding. In post #54 I was just asking for confirmation about what I'm supposed to read when taking measures on those pins, just to be sure though it wasn't really necessary.
Indeed, I had previosly (or maybe in the same post) said that I couldn't check promptly but within the next days as I've done afterwards.

@John843883

I've fitted back the diodes I had removed to check them then just connected the power supply to a power outlet and taken the measures. Nothing else was connected and the board wasn't fitted on the television neither. According to your question and also what you were previously suggesting about the need for the screws to be well tightened, I fear this could be the wrong way for doing this but I hadn't any alternative because I hadn't the tv at hand but only the PSU. I'm looking forward for a confirmation about that to take all the measures again. Should this be the case, I apologize for giving misleading informations though it wasn't my intenton.

Thanks to everyone!

[dick_barton]

Re: VESTEL 17IPS61-3 shorted output diodes

@dick_barton
I apologize for the misunderstanding. In post #54 I was just asking for confirmation about what I'm supposed to read when taking measurements on those pins, just to be sure though it wasn't really necessary.
Indeed, I had previosly (or maybe in the same post) said that I couldn't check promptly but within the next days as I've done afterwards.

Sorry, it wasn't meant as a criticism. Each helper has their own idea of what may be wrong and then make suggestion so that they can rule in or out their thoughts.

[John843883]

Re: VESTEL 17IPS61-3 shorted output diodes

@dick_barton

I apologize for the misunderstanding. In post #54 I was just asking for confirmation about what I'm supposed to read when taking measures on those pins, just to be sure though it wasn't really necessary.
Indeed, I had previosly (or maybe in the same post) said that I couldn't check promptly but within the next days as I've done afterwards.

@John843883

I've fitted back the diodes I had removed to check them then just connected the power supply to a power outlet and taken the measures. Nothing else was connected and the board wasn't fitted on the television neither. According to your question and also what you were previously suggesting about the need for the screws to be well tightened, I fear this could be the wrong way for doing this but I hadn't any alternative because I hadn't the tv at hand but only the PSU. I'm looking forward for a confirmation about that to take all the measures again. Should this be the case, I apologize for giving misleading informations though it wasn't my intenton.

Thanks to everyone!

Fair enough. Well sometimes these power supplies don't provide the right voltages without a load or at times won't start up the main rails without an "on" signal from the TV control board.

If you don't have the TV handy then maybe some resistors would suffice across the 12v and 24v voltage rails, aim for say 1 amp draw on the 12v rail and .5 amp on the 24v rail (doesn't have to be exact). You might have to trick the power on by feeding about 5v into the "STBY_ON/OFF" pin, a PP3 9v battery could also work but add a few extra k of series resistance. Its all in the schematic link I posted.

But if you can get hold of the TV it came from then it might save you a lot of time as we don't know what the power supply will do without the load it was designed for.

[vinceroger69]

Re: VESTEL 17IPS61-3 shorted output diodes

i would re connect all of the boards and take all the psu measurements again then we can see what voltages etc are missing if any

[guybrushthreepwood]

Re: VESTEL 17IPS61-3 shorted output diodes

I've mounted everything back. Just to recall the symptoms: solid red led when I connect the tv to the power outlet, blinking red forever as soon as I try to turn it on by the remote.
Here are the new values I've got:

1 GND (or at least it seems shorted to ground; this makes pair with the schematic according to which pin 1 is connected to ground through a switch)
3 1.91V
5 0.00V
7/9 0.01V
11/14 8.54V

While I couldn't take a measure on pins 13 and 15 because they haven't a connector soldered to them and their pads are downwards with the board fitted. I should have tried with a needle or something similar but I hadn't one at hand but I guess I had got the same reading than pin 11 on pin 13 (8.54V) and 0.00V on pin 15 as when the board wasn't connected to anything.
The numbers resemble the ones in the attached photo:



I don't know what to think...

[dick_barton]

Re: VESTEL 17IPS61-3 shorted output diodes

Starting again from scratch.
If you disconnect the main board from the power supply then switch on can you measure +5V at pin 9 of CN2. Black meter probe on the metal chassis.

If the 5V is present then power off and with the main board still disconnected short pin 9 to Pin 3 (STBY_ON/OFF). Power up the set.
Is there 12V on Pins 13 &14 and 24V on Pin 15

Be careful not to short any of the pins on the connector with your red meter probe or you'll have more problems than you started with. Black meter probe stays on chassis.

[guybrushthreepwood]

Re: VESTEL 17IPS61-3 shorted output diodes

First of all, thanks for your advices as always! Just a dumb confirmation... Given that you say to take all the measures with the mainboard disconnected but on the other hand you talk about powering on/off the set, I assume I'm supposed to short pin 3 and 9 each time (I guess doing it powers on or off the set according to its current state).
Am I wrong? For what concerns not shorting anything, I've always taken great care about that, don't worry!
Thanks again and good evening!

[dick_barton]

Re: VESTEL 17IPS61-3 shorted output diodes

You can use a 1K resistor to connect the pins 9 & 3 together. Then with the main board still disconnected switch on the set at the mains supply and measure the voltages at pins 13, 14 & 15.
You can remove the resistor after you have measured the voltages on those pins.

[guybrushthreepwood]

Re: VESTEL 17IPS61-3 shorted output diodes

Hi and thanks for your help. Right now I haven't a 1K resistor at hand: it would take me a while to get hold of one. If your advice is using it, I suppose just shorting pin 3 and 9 with a wire isn't a good idea otherwise I could have taken the measures today, it's a pity!
When you say "switch on the set at the mains supply" I assume you're talking about a switch for the PSU but the television hasn't one so I assume I would just need to connect the cord to the power outlet but, should my assumption be right, in post #60

The readings are very strange, here they are:

3 -0.02V
5 0.00V
7 0.06V
9 0.00V
11/13/14 11.18V
15 0.00V

I know that according to the schematics for the board I'm supposed not to be getting any voltage reading on pin 11 but I've double checked. Also, pin 11 isn't NC as in the schematics but connected to a resistor.
Another difference is that pin 14 and 18 are bridged.

I've already made that (all the measures were taken with the mainboard disconnected though the problem could well be the fact that the PSU wasn't screwed on the metal plate; I'm confident the reason for the bad readings could be that according to the previous advices I've received) and on pin 9 I've got 0.00V instead of 5.00V that are needed to switch the set on shorting it with pin 3 and making the other measurements on pin 13, 14 and 15 afterwards. This is strange because with the mainboard connected the set actually turns on though it stays with black screen and blinking red led and this seems to confirm my previous thought.
Given that the mainboard needs to be disconnected, is the same valid for the backlight cable too or not?
I apologize for my recurrent requests for confirmations but the reason for them is the same one why I take so much care about avoiding shorts or anything else: I'm conscious every bad move could lead to much worse issues than the actual ones, no matter how little it could be.

[dick_barton]

Re: VESTEL 17IPS61-3 shorted output diodes

Normal procedure for testing the power supply is to have it isolated from the main board.

Using a 1K resistor is just for safety, in the event that you miscalculate the pin numbers and connect to the wrong pin or to ground so it protects the +5V supply. So the first resistor is connected between +5V and STBY_On/Off

If this is successful in bringing up the other supplies then the next test would be to switch on the backlights. To do this you leave the first resistor in place and use a second 1K resistor from +5V to BL_ON (backlight On pin).

Switch on the set....yes, plug it into the wall socket.

[guybrushthreepwood]

Re: VESTEL 17IPS61-3 shorted output diodes

I've disconnected everything from the PSU and left it screwed to the metal plate behind the led panel, connected it to the wall socket and I've got EXACTLY the same readings of post #60. Being the only difference the fact that back then the PSU was on a table instead of being screwed to the metal plate inside the tv, I believe that screwed or not it doesn't make such a difference but I may be wrong.
On pin 9 I get 0.04V (the previous time I got 0.00, not a big deal anyway) and at this point I don't undestand how the tv can show even the most basic sign of life (as said, the led red blinks) when everything (including the mainboard) is fitted back, given that the voltage on pin 9 is the signal which turns the set on, at least by what I've understood.

[guybrushthreepwood]

Re: VESTEL 17IPS61-3 shorted output diodes

Unfortunately, this is beyond my knowledge but I was taking a look at the schematic. It seems that the STDBY_5V voltage is generated by this circuit:



from the 12V. According to the measures taken on CN2, 12V are almost there (I get 11.18V) unlike STDBY_5V so the problem could reside there, couldn't it?
There are a couple of components that draw my attention and they are D15, Q5 and Q10. I'm clueless on how to test Q5 and Q10 but I know how to test D15: could it be a useful thing or is it just a waste of time? I know I'm shooting in the dark but I don't know what else to think...

[guybrushthreepwood]

Re: VESTEL 17IPS61-3 shorted output diodes

Both Q10 and Q5 are NPN transistors and I've found this guide:

http://www.instructables.com/id/HOW-...R-MULTIMETERS/

showing how to test them with a multimeter. It seems very easy, the problem is that Q10 isn't present on my PSU (I've found the place for it but it is empty) while I couldn't find Q5 and D17 at all. I'm completely lost and I'm starting to think about buying a replacement PSU in the hope it is really the problem though I'd like not to give up so soon...

- EDIT -

I've unscrewed the PSU again and taken a look at the lower side. I've found Q8 and Q12 but not Q5 and it seems there isn't any other transistor. I've also found the marking on the board for D17 but there isn't any component near there. By the way, all of them are SMD components and I don't even dare to desolder them (by what I've understood even transistors need to be taken off the circuit to be tested).

[guybrushthreepwood]

Re: VESTEL 17IPS61-3 shorted output diodes

What do you think about my last update? Am I following a completely wrong way or what?
Thanks in advance for your advices!

[dick_barton]

Re: VESTEL 17IPS61-3 shorted output diodes

With the main board disconnected and the power supply "ON" what voltage do you have on each of the 4 diodes from left to right of the photo.

You also have quite a number of 0 ohm resistors on the underside of the board. With the power off and meter set to ohms they should all read 0 ohms when you place you meter probes across each of them.

[guybrushthreepwood]

Re: VESTEL 17IPS61-3 shorted output diodes

Measuring the resistors it's easy and I'll do it ASAP. For what concerns voltage through the diodes, I haven't ever done anything similar and I'm not sure about how to do it... I've tested those diodes off circuit with the diodes tester function of the multimeter and they aren't shorted so they definitively seem fine.
I see in the photo that you've pointed arrows on their catode and I don't think it is an unwanted case. Maybe I need to put black probe on GND (the chassis or the back of the lcd) and the red one on the catode (though the catode is the negative terminal)? I don't think so and I think it makes more sense if I respect the polarity of the diode, testing it as I had done with the diodes tester function but using continuos voltage instead.
It is starting to be a lesson on how to troubleshoot electronics more than something related to the PSU itself and, given that we're slightly off topic (I apologize for that), I'm starting to understand why no one apart from dick_barton (I wouldn't ever thank him enough!) is replying...

[dick_barton]

Re: VESTEL 17IPS61-3 shorted output diodes

Testing the diodes off the board is good, however it does not tell you what if any voltage is present at that point in the circuit.
With the black meter probe on the chassis use the red meter probe to measure the voltage at the cathode of each of the diodes. Set your meter to 20V DC or greater.

[guybrushthreepwood]

Re: VESTEL 17IPS61-3 shorted output diodes

I apologize for not coming back before. I have taken the measures. From left to right in the photo posted by dick_barton, I get 11.2V, 11.2V, 11.2V, 21.3V.
I've made the assumption that, as before, PSU on means just it being connected to the wall outlet, no shorts or else has been done.
Have a good day!