Westinghouse L2410NM No Power, No LED

[sambul83]

Re: Westinghouse L2410NM No Power, No LED

I use this calculator to figure our Resistor value, it blocks reverse color readings.

Unfortunately, I don't have ESR Meter, the values 2 mOhms / 1.4 mOhms refer to MegaOhms, may be I should put it 2 MOhms / 1.4 MOhms in-circuit, sorry about that.

[budm]

Re: Westinghouse L2410NM No Power, No LED

OK, if I were you I would replace those two caps, measuring the resistance of the cap does not really mean much, it may show leakage resistance and that is about it, it does show if it has correct capacitance.

[sambul83]

Re: Westinghouse L2410NM No Power, No LED

I will replace these 2 caps. Is that all for the power factor correction area of the board?

Interesting read for novices: Anatomy of Switching Power Supplies.

Anything to check on the Main Switcher side? Or its better to do, once PFC section is fixed?

On the Secondary Stage side, re DS4 and DS5 pads, since the rectifiers are mounted on a heatsink, I feel it may be possible to fix these lifted cooper pads back to the board without shorts. At the very least I can try that. Do you think, any parts on the secondary need replacement too?

Tiny CS2 cap measures OL/OL. Its the same size as the tiny cap right of DS5 that also measures OL/OL, and the missing tiny cap next to it. So all 3 of them likely have the same voltage (5.9V measured) and capacitance - correct? How to figure out their specs?

Should output voltages on DS4, DS5 and DS7 change when changing LCD resolution? I mean, can these rectifiers affect control functions of the Main Board, if their circuits malfunction due to lifted pads?

[kaboom]

Re: Westinghouse L2410NM No Power, No LED

My theory is, components age together, so injecting new ones in large numbers puts a lot more stress and disbalance everywhere on the boards, leading to more damage soon. So it makes sense to find the failing part rather than replace everything blindly.

I got your PM.

The only parts that really age are the electros, and in the case of your LCD, the CCFL backlights too.

That theory of "imbalance" doesn't hold water.

I am talking about the PFC CONTROLLER IC U2 L6561, the smps IC is working because you are getting the output voltages.

Yes, but barely. W/o the booster, the SMPS has too little to work with, perhaps it's right on the edge and dropping out with dips in his line voltage.

A picture of the PFC FET source resistor would help.

Be careful, as that board's looking a bit rough. I see some lifted pads.

[budm]

Re: Westinghouse L2410NM No Power, No LED

"Yes, but barely. W/o the booster, the SMPS has too little to work with, perhaps it's right on the edge and dropping out with dips in his line voltage."
That is what I have been trying to explain from post 44 and on and the SMPS is working but not the PFC, the circuit for the 24V power supply and the inverter circuit will need to have boosted circuit supplies the correct Voltage to run properly, at 180VDC is not going to cut it.

[sambul83]

Re: Westinghouse L2410NM No Power, No LED

Here're the resistors. But I read color codes and calculated values correctly.

I'm more concerned now how to find out value of CS2 ceramic cap, and the other 2 identical to it next to DS5?

[selldoor]

Re: Westinghouse L2410NM No Power, No LED

I'm more concerned now how to find out value of CS2 ceramic cap, and the other 2 identical to it next to DS5?

You keep asking that but Budm has already told you
"they are MLCC- Multi layer Ceramic Capacitors. no way to tell the value without the cap meter."

Without a meter all you can do is measure the size and get some the same and hope they work - voltage wise be guided by adjacent components.

Looking back at the original problem did you rule out faulty mains socket/ plug
/wire . Did you try in another mains socket and confirm it was not connected through a ups, surge protector or extension cable.

[sambul83]

Re: Westinghouse L2410NM No Power, No LED

All my equipment is connected through UPS units, and this one was too. Despite this fact, other equipment works properly. When being repaired, the unit was connected to either wall outlet or surge protector, which also work normally with other devices.

Re cap meter, in another thread it was mentioned that such tiny caps are very sensitive and once removed can't be placed back. It presumes they will be destroyed by heat upon removal. So even if I were able to measure its capacitance (or ESR?), such measurement wouldn't look trustworthy. In other words, its not clear how to measure their specs?

[sambul83]

Re: Westinghouse L2410NM No Power, No LED

W/o the booster, the SMPS has too little to work with, perhaps it's right on the edge and dropping out with dips in his line voltage.

You're possibly right, but on the other hand voltage on the main cap was 180V instead of targeted 169V. In that scenario wouldn't SMPS have too much to work with rather than too little? Of course, it can possibly also lead to protection caused drops.

I'm not questioning opinions here but trying to find logic why this board was failing that would hopefully help others in their search for a root cause. A standard way of replacing all caps may not help novices address all variety of failures in modern electronics. Besides, caps now are of much better quality than during Capacitor plague war, unless of course some device makers purposely aim at 3-year model recycling. Yet I don't see how a new monitor would serve me much better than this one.

[selldoor]

Re: Westinghouse L2410NM No Power, No LED

Re cap meter, in another thread it was mentioned that such tiny caps are very sensitive and once removed can't be placed back. It presumes they will be destroed by heat upon removal................ In other words, that suggestion needs some validation.

Which thread ? If that were so they would be destroyed when fitted to the board?

If you cant replace them it seems pointless to continue.

I am still not convinced that for one reason or another your line voltage
was steady and sufficient for the power supply board to maintain the minimum voltages for the board components to work to their full and required extent.

[sambul83]

Re: Westinghouse L2410NM No Power, No LED

Thank you for the valid concern. Not sure, I can do much about it. And that should correlate with other devices similar failures - correct?

Yes, our power grid gives us surprises all the time, especially weather dependent. I read on one German forum a lady asked "why do you need so many UPS units in North America, when we have NONE in our homes"? And that was probably a valid question too, only addressed to the wrong folks.

[budm]

Re: Westinghouse L2410NM No Power, No LED

I still say that the boosted PFC Voltage is not correct, why bother to boost 160V to 180V only instead of typical 360~400V range.
Higher Voltage lower current so they can use lower current rating device, smaller traces, etc.
Beside why would they put in 420VDC cap and PFC circuit, they cost money just to boot the Voltage 180V?

You use UPS if your area has a lot of blackout, our here where I live, it may happen only 3~4 time a year. Most ups these days also can function as AC buck-boost regulator to maintain 120V (+/- 5VAC or so) before it goes into UPS when lost power or the AC Voltage is beyond AC regulation range, it also has surge protection built-in.
So how much are the equipment worth to you if they go down due to brown out, over voltage, or surges?

[sambul83]

Re: Westinghouse L2410NM No Power, No LED

I tend to agree with your line of thought, despite you mentioned here it should be 169V. However, from practical standpoint, what parts are the problem - C21 and C22 caps? I will definitely replace them, but something tells me it won't raise voltage twice on the main cap though who knows... I checked everything else in-circuit, the results posted above seems to be OK? The only thing I noted, TEA1552 controller. It measures 11.01-11.4V btw GND pin 10 and VCC pin 8, while its spec seems to set it at 15V - does it ring the bell?

I question though whether its possible for a LCD to operate at all (and it did for hours) if target voltage dropped 2 times lower? But again, electronics isn't my field of knowledge.

Despite frequent weather driven outages and surges in particular during heavy snow and ice on wires in winter, strong winds in the fall, and lightning in spring (yes, its Jurassic Park kind of habitat ), we had frequent outages, but no equipment damage from that whatsoever, as its all hooked to UPS units. This monitor flickering is caused by parts aging, and is typical for this particular model as several threads only on this forum suggest. This is also true for other failing equipment, where part cost cuts (think of CapXon) prevail at design and production stages.

[budm]

Re: Westinghouse L2410NM No Power, No LED

1) TEA1552: I f you read the spec sheet, the VCCstart Voltage has to reach 11V on the startup-running cap connected to the VCC pin. Once the circuit running as long as it stays above 8.7V it will keep running, if it goes below 8.7V the under voltage lockout circuit will kick in and stop the operation. Max VCC the TEA1552 can handle is 20VDC, so once it starts running the Voltage can be between >8.7V and 20V max.

2) The PFC Controller IC does not use the same startup/UV lock down point.

3) If the caps for VCC of the PFC IC has resistance leakage (measured using cap analyzer) or the internal resistance of the IC is bad, then the startup voltage will not reach.

4) Check the DCV between the two legs of the filter cap to see if it is maintained at 180V or if it is drifting up and down with the flickering of the backligts, it should stay steady .

[selldoor]

Re: Westinghouse L2410NM No Power, No LED

[QUOTE=sambul83;554020]Here're the resistors. But I read color codes and calculated values correctly.
QUOTE]

You may think you did but I have been thinking that budm is seldom wrong
and wonder if the colours are for E24 resistors Brown Green SILVER Gold and Green giving approx 0.15ohms (you did say originally you measured it at 0.2
ohms. I also seem to recall that Budm once advised me and an OP that some
manufacturers use yellow for gold as the metallic colors are not suitable for
some types of fuse. So maybe silver is not suitable for this grey casing?

[budm]

Re: Westinghouse L2410NM No Power, No LED

BTW, so far you do not have cap meter to measure the ESR, the capacitance, etc and you do not want to replace the caps (in the power supply and in the inverter board) due to your believe that new caps will cause stress to the circuits, so I have no more advice for you, it ends here for me. I have much better thing to do instead of giving times for free advice at BCN.
BTW, please study the spec sheet of the ICs so you will understand how they function.

[sambul83]

Re: Westinghouse L2410NM No Power, No LED

I repeated 3 times already that I will replace the 2 caps no matter what I believe into. If you think of inverter board caps, will order them too. Greatly appreciate your advice regardless whatever you choose to do. Again, I don't question anyone's opinion, just trying to think laud as always, but sorry this is the last time I will explain that.

The problem is, this power supply has damaged tiny caps with unknown values. As to the R12 resistor, it still has 0.2 Ohms reading, so its quite possible that color coding is mixed up. Anyway its reading is the only thing that matters.

Based on the above advice, until C21 and C22 caps are replaced (which I need to procure now), no way to progress with this repair. And if values of tiny caps aren't found, this thread would still retain high diagnostic and learning value. And this monitor will still definitely be repaired. Not sure what else to say to keep everyone happy. If I had stock of these caps, the issue would be rectified immediately. Given extreme DigiKey choice, selecting proper stock would be a challenge.

Another thing I discovered this PS was also used in ViewSonic VX2435wm and VS11449 models under p/n 098-32043-02, which is important to locate spares. Otherwise I already contacted APD for dillers info & replacement hints. Don't think they will share its schematics, but who knows. Interesting trend, newer LCD PS models I seen become larger in size, with heatsinks mounted aside from components. It may be result of higher return rates & cost of warranty repairs overweighting savings in production.

[sambul83]

Re: Westinghouse L2410NM No Power, No LED

BTW, so far you do not have cap meter to measure the ESR, the capacitance, etc ...
BTW, please study the spec sheet of the ICs so you will understand how they function.

I've capacitance meter, but no ESR meter. I will provide some more info for future readers.

R12 @ 0.2-0,3 Ohms next to D2 - see above. It's color coded: green - gold - white - green - brown, which seems to mean 15.9 Ohms +- 0.5% as per Resistor Calculator.
R31 @ 0.1-0.2 Ohms next to large transformer: green - gold - white - grey - black (no match). So it looks like R12 and R31 have non-standard color-coding
Ra1 @95.3 KOhms next to Q1. Color: brown - black - yellow - gold rated @ 100KOhms

Based on PFC L6561 datasheet, the output voltage on the large cap CK1 is regulated based on current readings passing through R1, R1, and Ccomp (Fig.5), which in this case seems to be R12, R31 and C21 & C22.

Examples Fig.6,7,8 show that nominal output voltage is chosen based on mains voltage and required output power in the range 110V/240V&80W - 220V/400V&120W, despite output cap spec is usually set to much higher voltage 315-450V probably for spikes protection & durability.

Westinghouse L2410NM spec says its power consumption is 105W that leaves a question whether 180V stable on the output cap CK1 is the design target or it should be closer to 240V? It feels somewhat low based on above examples, but can caps C21 and C22 play a vital role in it - yes, since they are part of the overvoltage protection circuit, which can set voltage threshold below design target due to these aged caps.

That in turn means kaboom's assumption that "the SMPS has too little to work with" is likely correct, while PlainBill's description "AC power is applied, the mains filter cap charges to full voltage (1.4 x line voltage) i.e. 169V" was likely too generic, not directly linked to this PS, as they didn't id properly PFC L6561.

Now it all makes a lot more sense for a novice like me who wants to understand what's up. BudM's recommendation to replace these caps sounds absolutely correct, and may be the key to fixing the flickering issue. My question "How LCD could operate for so long on greatly depressed voltage" may be argued by the fact that target output voltage may not differ that much from now measured 180V, if the caps 21 and 22 capacitance is only partially changed.

Btw, many reports blamed faulty firmware HDCP protection related HDMI handshake for LCD periodic flickering, but given the fact flickering frequency depends on outside temperature changes in my case, it looks more like PS component(s) fault, since their operational specs can be slightly affected by small temperature variations, while firmware can't be. Yet again, HDMI handshake fault was reported to be periodic, hence also probably operational conditions dependent.

[sambul83]

Re: Westinghouse L2410NM No Power, No LED

Looking at PS label: APD FP-120A01
Input 100 - 240VAC, 50-60Hz
Output 5, 14.5, 24 VDC

The unit is universal, it explains higher specs for some parts like the main cap 420V 120uF. However, if input voltage is twice below max, target output may be proportionally lower too, though FPC datasheet Fig.8,9 show 400V output for Wide Range input application.

As to SMPS IC Tea 1552, the datasheet says:
"Initially, the IC is self supplying from the rectified mains voltage via pin DRAIN. Supply capacitor CVCC is charged by the internal start-up current source to a level of approximately 4 V or higher, depending on the drain voltage. Once the drain voltage exceeds the M-level (mains-dependent operation-enabling level), the start-up current source will continue charging capacitor CVCC (switch S1 will be opened); see Figure 1.
The IC will activate the power converter as soon as the voltage on pin VCC passes the level VCC(start). The IC supply is taken over by the auxiliary winding as soon as the output voltage reaches its intended level and the IC supply from the mains voltage is subsequently stopped for high efficiency operation (green function).
The moment the voltage on pin VCC drops below the undervoltage lock-out level VUVLO, the IC stops switching and enters a safe restart from the rectified mains voltage. Inhibiting the auxiliary supply by external means causes the converter to operate in a stable, well defined burst mode".

That's what selldoor probably mean when talking of mains voltage drops, which can lead to SMPS stop and restart thus resulting in monitor flickering with audio loss. The question is how value of its aging C10 cap can affect that? Lower residual capacitance would result in less ability to compensate for cycling mains drops. Not sure if it applies here, since mains voltage rather fluctuates with 24-hour cycle, not rapidly.

Another issue is how to check, if the main cap voltage stays steady when monitor is flickering. With these tiny secondary caps damaged its hard to do without risking to damage Main and Inverter boards. Its not easy anyway, as flickering starts within 2-3 hours after normal operation, and you never know how many times it will flicker before getting back to normal again. The flickering is very short 1-2 sec, so basically the cap voltage needs to be recorded continuously to register that event. Its still possible to catch the 1st event and start monitoring.

Now, someone may ask, why go to such depth if you can simply replace all caps? The reason is, knowledge holders here apply similar logic but fast and almost automatically, they don't replace caps for fan, but analyze the circuit for problem root cause. I doubt success is guaranteed by blindly (say stupidly) replacing random parts. On the contrary, another thread here on same monitor repair shown almost 100% failure rate within 6-months after caps replacing with more serious damage than the original, resulting in Main and Inverter boards replaced. Another thing is, if you have enough skills you wouldn't ask questions here. Then imaging how much extra damage you'll do to the board while trying to replace multiple caps despite none of them may be relevant to your board issue.

[sambul83]

Re: Westinghouse L2410NM No Power, No LED

I think at this point it is time to buy new power supply board.

After a long wait finally I was able to procure a used one from China via Wisiny.com . It seems to work OK, and the site claims to give 180-day warranty. This power supply model is listed on quite a few sites including Aliexpress, but none has it in stock for awhile since the supplier stopped making them, and the monitor makers' warranty expired.

Voltage on CK1 big cap for this board is 192V stable compare to 180V on the original one. After heating up, the monitor started flickering again, but somewhat differently. With old PS, it was shut of for some time at each flickering with HDMI text shown in top right corner, and kept flickering 3-6+ times in a row, then going back to normal work for 2-3 hours. Now it flickers briefly once in every hour or so, with no HDMI text shown on screen, probably due to shorter flickering cycle. Any ideas, what can still cause this flickering? May be its really HDMI handshake problem with this monitor? But then how it was working for days hooked to a PC via HDMI without any flickering in this case despite being extensively used 12+ hours a day with constantly changing on-screen content?