Samsung LE32S73BDX No power not faulty caps

[reidy-]

Hi, I have the above TV with a BN96-03775A power supply schematic here:



The symptoms are; when you apply power to the TV the LED goes solid red and does nothing else (a small whine noticed near the large transformer) when any other input is applied i.e. change channel the front LED just flashes on and off repeatedly

I have don a small amount of testing and have confirmed all the large capacitors to be in good condition (+/- 10%) and no IC's have been visibly burned.

when I tested the 24V rail on standby it is solid at roughly 24.3v but as soon as the power button is pressed it drops off rapidly to 4v then tends slowly down to <1v

I have read that the f9222l IC is a common culprit in such PSU's could you advise how to confirm that this is the case and any more measurements that I should do?
there has also been talk of another IC TDA4863G but have read little about this.

thanks in advance, Reidy-

[PlainBill]

Re: Samsung LE32S73BDX No power not faulty caps

Hi, I have the above TV with a BN96-03775A power supply schematic here:



The symptoms are; when you apply power to the TV the LED goes solid red and does nothing else (a small whine noticed near the large transformer) when any other input is applied i.e. change channel the front LED just flashes on and off repeatedly

I have don a small amount of testing and have confirmed all the large capacitors to be in good condition (+/- 10%) and no IC's have been visibly burned.

when I tested the 24V rail on standby it is solid at roughly 24.3v but as soon as the power button is pressed it drops off rapidly to 4v then tends slowly down to <1v

I have read that the f9222l IC is a common culprit in such PSU's could you advise how to confirm that this is the case and any more measurements that I should do?
there has also been talk of another IC TDA4863G but have read little about this.

thanks in advance, Reidy-

You've got something backwards here. 24 volts and the other operating voltages are produced on page 2 of the schematic. If I read this correctly, they should be at 0V when the TV is in standby. Standby voltage is 6 volts and is produced on page 1.

PlainBill

[reidy-]

Re: Samsung LE32S73BDX No power not faulty caps

Be that as it may, that's how its operating :S

I could check some more voltages tomorrow morning if you wish i.e. the 13v & 4.5v rails. I will also check pin 2 on the bottom right of page 2 which will find out if its in standby or not.

is this unusual? I have seen references of other people seeing 24v at standby albeit its a different monitor they talk about the 24v source being hand in hand with the 5.3v stand by. maybe it doesn't apply to this case I am not sure
https://www.badcaps.net/forum/showpo...7&postcount=45

[PlainBill]

Re: Samsung LE32S73BDX No power not faulty caps

Be that as it may, that's how its operating :S

I could check some more voltages tomorrow morning if you wish i.e. the 13v & 4.5v rails. I will also check pin 2 on the bottom right of page 2 which will find out if its in standby or not.

is this unusual? I have seen references of other people seeing 24v at standby albeit its a different monitor they talk about the 24v source being hand in hand with the 5.3v stand by. maybe it doesn't apply to this case I am not sure
https://www.badcaps.net/forum/showpo...7&postcount=45

Definitely check if it's in standby.

I'm looking over the schematic; some of it is easy to understand; the rest is giving me a headache. I swear, the first 32" 1080p TV I fix is gong on my desk as a second monitor. Of maybe I should have something like the setup from 'Swordfish' (Halle Berry optional).

IPS801S is the standby SMPS controller. It's always on. TS801S pins 1 & 2 are the primary of the standby transformer. 3 & 4 are the tertiary winding that provides Vdd. 5 & 6 are a second tertiary winding that provide power for the On/Off circuitry and the PFC controller. Pins 9 & 11 are the secondary; it provides only 6 volts. PC805S(?) provides feedback for regulation. That's all a standard SMPS design.

Now when On/Off is high PC801S is turned on, pulling the base of QS801 high, and since it's an emitter follower, the emitter also rises. This provides power to the collectors of QS802 and QS803, both of which are wired as emitter followers and provide Vcc to the PFC controller ICP801S (15V) and M_Vcc, (18V).

DZS851 and DZS852 had me puzzled. My best guess is if either 24V or 5.4V rises too high QS852 is turned on, and PC802S conducts, pulling M_Vcc2 high. And I'll be darned if I can figure out what that is for.

On to page 2!!!

Everything on the hot side is standard EXCEPT for M_Vcc ans M_Vcc2. I can't fathom what is going on there. It looks like they are redundant supplies for ICM801S??? On the cold side regulation is handled in the usual way, with PC803S providing the isolation. This regulates the 13V supply. The 24V supply just follows along, and the 12V and 5V supplies are developed by independent regulators, drawing their power from the 24 volt supply.

So the first step would be to ignore the front LED. Push the On/Off button until you have the main supply voltages - 24V, 13V, 12V and 5.4. If any of them are missing troubleshoot that portion of the supply.

I think you may be misinterpreting the function of the power LED. On at least one set I have, the power LED is red when the set is off, it turns green when the set is turned on. The red flashing may indicate an error condition. Does it display any pattern (5 blinks, pause, 3 blinks, long pause, 5 blinks, pause, etc)?

PlainBill

[reidy-]

Re: Samsung LE32S73BDX No power not faulty caps

Thanks alot PlainBill that's the kind of insight you pay for!!!

did a bit more testing and got some strange results.

If I am correct I think standby is at 5v and when the set is turned on it rises to 6v or is it vice versa?

Well on standby when the solid red light is on the standby (pin2) is at 6v stable then when the power button is pressed there is no active change and it remains at 6v

the 5.4v rail was also a bit strange in the sense that at powering up at the wall socket the front LED was not on.
at standby it held 5.35v stable and when powered up it tended to 0v instantly

12v rail was 0v at standby (if we can call it that) then when the power button pressed it shot straight to 12v and remained there happily

Hope this offers some more insight, I'll have a think and do a bit more testing (forgot to do the 13v rail)
what makes the s/by rail start at 5v then go to 6 it looks like something there will need replacing.

many thanks, Reidy-

p.s. all tests were undertaken with every board in place and connected

[reidy-]

Re: Samsung LE32S73BDX No power not faulty caps

10min message edit limit forced me to make a new post:

just conducted the 13v test

at standby (however no LED lit) the rail was stable at 12v
as soon as the power button was pressed the rails tended to 0v

[PlainBill]

Re: Samsung LE32S73BDX No power not faulty caps

Thanks alot PlainBill that's the kind of insight you pay for!!!

did a bit more testing and got some strange results.

If I am correct I think standby is at 5v and when the set is turned on it rises to 6v or is it vice versa?

Well on standby when the solid red light is on the standby (pin2) is at 6v stable then when the power button is pressed there is no active change and it remains at 6v

the 5.4v rail was also a bit strange in the sense that at powering up at the wall socket the front LED was not on.
at standby it held 5.35v stable and when powered up it tended to 0v instantly

12v rail was 0v at standby (if we can call it that) then when the power button pressed it shot straight to 12v and remained there happily

Hope this offers some more insight, I'll have a think and do a bit more testing (forgot to do the 13v rail)
what makes the s/by rail start at 5v then go to 6 it looks like something there will need replacing.

many thanks, Reidy-

p.s. all tests were undertaken with every board in place and connected

I'm not sure how much experience you have with troubleshooting digital TVs. A number of the usual 'rules' must be thrown out.

The power LED is controlled by one of the processors. It may actually be reversed from what we are used to - I had one that turns the red power LED OFF when the TV is turned on (in case someone with a sensitive ego doesn't want to see a red LED while watching TV, I assume).

When first plugged in, the set may not go into standby. Some of them will resume the last state. So if it died while powered up, it will try to turn itself on when plugged in.

They often have extensive self test capabilities. They may or may not flash the nature of a failure.

Humor me, do this. Unplug the TV, let it sit for 5 minutes. Plug it in, measure all the power supply outputs: 24V, 13V, 12V, 5.4V, Standby. Push the power button once. Measure the voltages again. Report the results.

24 volts and 13 volts come directly from the main power supply. 12 volts and 5.4 volts are produced by regulators drawing power from the 24 volt supply. I would not be alarmed if the 24 volt supply varied a little bit. And don't believe that the RED LED means 'On'.

Have you found the Service Manual for the TV?

PlainBill

[reidy-]

Re: Samsung LE32S73BDX No power not faulty caps

Right this is mad and I cannot for the life of me explain any of this but here goes...

I did what you said but by complete accident had left the TV inverter board unplugged

and got the following results:

voltage: off on

24v ~0v 24.3v

13v ~0v 11.94v

12v ~0v 11.98

5.4v ~0v 5.35v



Now after this I plugged the inverter back in and repeated the test


voltage: off on

24v ~0v 24.29v

13v ~0v 12v

12v ~ 0v 12v

5.4v ~0v 5.3v


the only explanation is that a part has warmed up and started working

I'd also like to note that I managed to get static sound (no Ariel plugged in) when the inverter board was not plugged in, I am now going to test with an ariel and see what happens.

my previous results were still correct I have no doubt about that there is something wrong with the power board. but I guess I now need to look at faulty transformers for the LED inverter board I guess?

[Wizard]

Re: Samsung LE32S73BDX No power not faulty caps

Samsung red LED is lit in standby. Off when running.

The 24V, 13V and main 5.3V are from one larger transformer is running when on. In standby this is not running.

BUT! Newer samsung combined standby and main into one transformer so you will have
mosfet switches for main 5.3V, 13V and 24V. Leaving the standby 5.3V constant power , this is same source off one 5.3V winding on the transformer as switched main 5.3V.

Not too hard to understand. Follow the PS-on.

Your measurements confirms power supply is good, and mainboard is responding to turn on/off.

Flashlight to the LCD while tv is on and in dim room, call up menu if you can't see snow to confirm LCD is working and that diagnosis also tells you if backlight had failed.

Cheers, Wizard

[PlainBill]

Re: Samsung LE32S73BDX No power not faulty caps

Wizard!!! Glad to see you back!

reidy-, hook up a signal source to one of the inputs - I use an old Nintendo to composite and audio inputs. Then step slowly through the inputs until you hear the audio.

PlainBill

[reidy-]

Re: Samsung LE32S73BDX No power not faulty caps

Thanks very much guys we have solved half the problem but it might come back to haunt us when the inverter gets fixed and starts drawing power.

as it stands the TV works just with no backlight, have tried the TV input (saw static back ground) and also the HDMI input and heard my xbox 360 making game related noises.


the TV starts up and every time the front LED flashes 4 times with a similar 1s time span then finally goes off indicating the TV is working

what should I be looking for, other than blown transformers?

[PlainBill]

Re: Samsung LE32S73BDX No power not faulty caps

Thanks very much guys we have solved half the problem but it might come back to haunt us when the inverter gets fixed and starts drawing power.

as it stands the TV works just with no backlight, have tried the TV input (saw static back ground) and also the HDMI input and heard my xbox 360 making game related noises.


the TV starts up and every time the front LED flashes 4 times with a similar 1s time span then finally goes off indicating the TV is working

what should I be looking for, other than blown transformers?

Shorted drive transistors, blown fuses.

It's been mentioned many times - a picture is worth a thousand words.

PlainBill

[reidy-]

Re: Samsung LE32S73BDX No power not faulty caps

best image quality I could get really, tried using a rather expensive SLR but it ended up even worse

http://img844.*************/img844/7897/p1010002x.jpg
http://img801.*************/img801/7594/p1010003p.jpg

I have sent an email to the inverter manufacturers requesting data but I have gone through every one and there all relatively similar nothing more than +/- 5% for impedances

I also noticed that one of the inverters had been changed (had a different code on it) but it still measured the same as the others

[PlainBill]

Re: Samsung LE32S73BDX No power not faulty caps

Before spending too much more of my time, what are the symptoms with the inverter plugged in? While this inverter bears a Samsung part number, it is made by Darfon. Darfon has a certain 'reputation'; it's not a good reputation.

Do a little searching for 4002P transformer and see if you can find one with the wiring diagram. I tore many follicles out over a Philips LCD TV with a similar inverter and transformer (4006P). When I measured the resistance of all of them one winding stood out and also failed the ring tester.

PlainBill

[reidy-]

Re: Samsung LE32S73BDX No power not faulty caps

The symptoms do not change when the inverter board was added.


Yeah don't bother going mad time wise however I did a couple more measurements and non of the inverters are outputting any voltage(measured the top clips), but the capacitors located at the bottom of the board are charged to 24v as supplied by the power board.

I measured the impedance from the 8 clips of the TV that go into the inverter board top and all of them measured as an open circuit is this normal?

could the physical backlite have died?

[reidy-]

Re: Samsung LE32S73BDX No power not faulty caps

scrap that its ultra high impedance because of the actual composition of the tube...

non of the inverters stand out impedance wise, and I did quite a thorough search earlier for a wiring schematic no such luck =/

I might have to end up buying one of these I found one in Japan very cheap and can always flog these inverts on ebay

[PlainBill]

Re: Samsung LE32S73BDX No power not faulty caps

The symptoms do not change when the inverter board was added.


Yeah don't bother going mad time wise however I did a couple more measurements and non of the inverters are outputting any voltage(measured the top clips), but the capacitors located at the bottom of the board are charged to 24v as supplied by the power board.

I measured the impedance from the 8 clips of the TV that go into the inverter board top and all of them measured as an open circuit is this normal?

could the physical backlite have died?

This is normal. The backlisghts are not LEDs, they are CCFLs. They don't start conducting until they get about 1000 volts across them.

Did you check all three fuses? The inverter will not work unless all three are good. Also, what is the part number of the 20 pin IC? The datasheet may give important clues.

Lastly, note the legend next to CN1. The state of the BLON line is also important.

PlainBill

[reidy-]

Re: Samsung LE32S73BDX No power not faulty caps

measured pins 11,12,13,14

pin 11 (NC) -0v
pin 12 (B/L on/off) 5.3v
pin 13 (ADIM) 3.1v
pin 14 (PWM) 5v

sorry about the large influx of data&posts (can't edit) I am pretty much past the point at which I know what I am doing, so just hoping if I pile through enough data you might be able to spot something out of place.

what does NC ADIM & PWM stand for? I was under the impression that the back light control sat at 3.3v to activate?

[PlainBill]

Re: Samsung LE32S73BDX No power not faulty caps

measured pins 11,12,13,14

pin 11 (NC) -0v
pin 12 (B/L on/off) 5.3v
pin 13 (ADIM) 3.1v
pin 14 (PWM) 5v

sorry about the large influx of data&posts (can't edit) I am pretty much past the point at which I know what I am doing, so just hoping if I pile through enough data you might be able to spot something out of place.

what does NC ADIM & PWM stand for? I was under the impression that the back light control sat at 3.3v to activate?

NC means 'No Connection' so of course it will read 0V

The threshold for the backlight turning on is typically 1-3 volts. It varies with the design. Depending on what is driving it, 5.3 volts is good.

ADIM is the analog signal that changes the screen brightness. I believe 3.1 volts would mean full brightness.

PWM would use a pulse of varying duty cycle to adjust the brightness. High 10% of the time would be low brightness, High 90% of the time would be full brightness. Or the reverse.

Now about the fuses? I can't read minds. If you don't answer I have no way of knowing if you checked all three and found them good or you're ignoring me.

Same deal for the 20 pin IC. It's the inverter controller.

PlainBill

[reidy-]

Re: Samsung LE32S73BDX No power not faulty caps

Hi the previous post were only 5 mins apart I must have started writing mine as you posted yours so I completely missed it

There are 3 fuse positions f1-3

f1 reads & f3 give a 20 ohm reading so test good.

F2 however doesn't actually have a fuse across it and there is just a diode in between the two pins where the fuse should be.


right, the CCL controllers full IC code is: MSC 1692IPW 0549B

the schematic for the controller is located here;
http://pdf1.alldatasheet.com/datashe...LX1692IPW.html

thanks, Reidy-