Westinghouse L2410NM No Power, No LED

[budm]

Re: Westinghouse L2410NM No Power, No LED

The power supply board has PFC Voltage booster circuit, so if you only getting 180VDC, then the PFC is not working, the Voltage on the main filter cap should be more than 360VDC (measured between the two legs of the cap).
The Diode you measured as shorted are not shorted, they are dual diode with common Cathode in the middle pin, the two outside pins are Anode and are tied together by the traces on the board to form parallel diode connections to handle the load current.
Your power supply is working but not at full potential due to the PFC is not working.
I will have to trace the bottom side of the board and also locate the PFC Controller IC to test the Voltages, the PFC diode D2 should also be tested.
You have already looked at this pictures and see the notes of what to check?
https://www.badcaps.net/forum/attach...0&d=1429619326

[sambul83]

Re: Westinghouse L2410NM No Power, No LED

It doesn't look like there're many helpers around. No problem, I'll continue the thread in a hope it can help others in the future.

Since rectifiers under right heatsink shown 0 Ohms btw G and S pins on-board, I kept testing them:

Voltages from the ground:

DS4 G - 5.9V, D - 22.1V, S - 5.9V
DS5 G - 5.9V, D - 0V, S - 5.9V
DS7 G - 5.9V, D - 10.7V, S - 5.9V

Not sure if these values are suitable given 5V, 14.5V and 24V power supply output? I suspect display resolution changes may require changing voltages, since the LCD goes black in btw different resolutions. Suspicious of DS5 D=0V...

I removed the right heatsink and all 3 parts to test off board. It wasn't easy by any means given lack of experience, multiple joints, and no way to reach rectifier screws. The best way probably is to add some solder to each joint, and then carefully remove all solder with cooper wick. Then try removing pins one by one by heating and pressing from bottom out with a screwdriver. I came to this through trial and error, lifted a couple of pads with solder vacuum in the process. Cooper wick absorbs solder much better if there is no pin sticking from the hole. Your iron quality and size makes all the difference. If someone tries this, prevent rectifiers overheating by hooking each to heavy locking plyers. Does lifting these pads make the board DOA?

Once removed, measured rectifiers resistance off board was:

DS4: G-S OL / OL, G-D 1.5 mOhms / OL, D-S OL / 1.5mOhms
DS5: G-S OL / OL, G-D 130 kOhms / OL, D-S OL / 130 kOhms
DS7: G-S 310 kOhms / 300 kOhms, G-D 300 kOhms / 40 kOhms, D-S 40 kOhms / 300 kOhms

Models:
DS4 456 SP10150
DS5 STPS20H100CT GKON7 VW CHN 702
DS7 STPS2045CT CC120V MAR 701

Do the above readings ring the bell - asking mostly myself for now?

More parts info:

The chip to the right of rectifiers looks like voltage regulator marked 4419 BA6515, more info here, but it doesn't feel relevant for me. This seems to be the right part.

I found some issues with very small caps on the board:

CS2 and both non-numbered caps connected in parallel to DS5 G pin measured OL on-board, it looks like they're open. One such cap was lifted with pad and removed. Can someone suggest suitable replacements or at least target part values? Also, what these lines of solder are for all around the board - are these extra cooling surfaces above pads, or to add some capacitance to pads?

I still want to think the board is salvageable since its harder now to find the same replacement. By any means it was great learning experience trying to fix my own electronics from ground zero, and learn in the process what to do, how and why. I will definitely fix the monitor.

[sambul83]

Re: Westinghouse L2410NM No Power, No LED

The symptoms are a bit different - no power versus flickering power, but everything else including diagnostics seems to be the same, as flickering is also due to intermittent power loss. Audio is lost too when LCD is flickering (getting dark), that's why I think of power supply problem.
Front led - 3.73V white light, sit size 4x4x4mm, was mounted in a way impossible to remove. Monitor works OK with or without it. Can someone suggest a suitable led model?

Voltages on all caps at idle:
C21 - 0.4V, C22 - 19.3V, C23 - 20.3V, CK1 - 180.3V (under left heatsink)
CS27 - 0V, CS28 - 0V (under right heatsink with Model Label)
CS21 - 16.7V, CS16 - 28.3V, CS18 - 28.3v, CS19 - 16.7V, CS11 - 16.7V

At idle only wires 5 and 6 on Main Board connector have voltage 16.6V , all other wires on main board and inverter board connectors are 0V. In post 7 above it was said: "From the label on the main power supply, it looks like this supply puts out 5V, 14.5V and 24V" under load. Than why so many wires are coming to inverter and main board connectors from power supply?

Resistance measured on board with power off:
C21,22,23 - OL
All other caps - varies around 50 - 200kHms

rectifiers (under left heatsink) - normal values as posted earlier in the thread
rectifiers (under right heatsink with Model Label) - 0 btw G and S on all 3, other values are similar to posted earlier in the thread. But they seems to work OK for hours under load until flickering starts a few times.
It was said in post 16 above:
"Resistance across S and G looks like it's almost shorted. You may need to do two things:
1) you will to need reverse your meter probes and re-measure the resistance across S and G for Q1 and Q2. If you get the same results, I would suspect a possible short. Step 2 below will verify it.
2) since Q1 and Q2 are "in circuit", other components could be affecting your readings. If so, it may require that you remove the mosfets from the board to get more accurate readings."

My question now is, how function of components set under left heatsink differs from the set under right heatsink? Does 1st set convert AC to DC, and the 2nd set drops source DC to 3 output voltage levels? The board seems to be divided on several sections, and other Power Supply boards are somewhat similar in design despite have different size. What's the main functionality of a PS board major sections - how this thing works?

[selldoor]

Re: Westinghouse L2410NM FLICKERING

You would maybe have been better starting your own thread as the heading doesnt reflect your problem. It is not usual to have to use the monitor you are trying to repair. What will you do if you accidently short something out?

Presume it still works without the power led if that is what broke - no idea what
you need to replace it.

As to flickering this is usually due to bulb on its way out. Bulb wiring on its way out. Inverter transformer on it way out. All of which are hard to find until they actually go, unless you can easily get to the ends of the bulbs?

It could also be a solder joint which is no longer 100%.

As you seem to think it is power relataed O would start by reflowing (replacing the solder) on all big high voltage joints - main transformer, main cap large diodes and large resistors.

iIf that doesnt help then replacing the 4 caps on the inverter board may help - the ones on there are not great. ( need good quality caps from a reliable seller should be 105 degree ones)

The list goes on and on - others may chime in with what they would check
replace first. Try searching through this displays forum for more ideas.
( use search -"flickering)

[sambul83]

Re: Westinghouse L2410NM No Power, No LED

I took the monitor apart again for some more "genuine" pics. Found that front led wire was accidentally cut too close to the led, so had to broke and remove the led from its sit. Can you guys suggest what led part number should I order now?

Removed the heatsink from Power Supply board. The main cap KMG 120uF 420V measured 180V stable at idle, with resistance 200kOhm growing slowly towards 1+ mOhm when removed, and capacitance 135uF firm. I put it back for now. What else would you suggest to check to ID flickering cause?

Is there a standard way to remove this white and yellow filler btw components? Why some of it white, and some yellow - due to different Temp rating? What I can replace it with to hold parts as it did?

[sambul83]

Re: Westinghouse L2410NM No Power, No LED

Sorry, I have to use the same monitor for posting on this forum that I'm trying to repair. In post #34 all pictures were taken by me. In post # 35 I posted the same boards already marked by others with appropriate part numbers and heatsinks removed, which I can't do due to using this monitor. But I can take any measurements. All earlier posted boards have the same part numbers as mine and visually look the same, the Inverter and Main boards seems to be in good shape, they are given mostly for reference here. Since I suspect Power Supply, I posted my pics for it. But if you feel, the culprit may be on another board, I can desolder all heatsinks and take other pics.

My logic is that Main board doesn't control flickering (display turns completely black for a few secs), and Inverter board doesn't control small speakers mounted inside this LCD's plastic case. Because flickering is supplemented by lost audio, it seems to be power supply problem. More, I can still type on the keyboard when display turns black, and when its lit again, I can see what was just typed in this post while it was black.

[selldoor]

Re: Westinghouse L2410NM No Power, No LED

Well I dont think there is time now for you to edit your post but by including pictures that are not YOUR boards you have made it very difficult to comment

[sambul83]

Re: Westinghouse L2410NM No Power, No LED

Below are more images of the monitor L2410NM boards, some were collected from earlier posts in this thread. I also noticed, my LCD flickering depends on the mains voltage variations.

Its strange though, why front led could be affected by wires running from PS to the Inverter board? The Main board sends signals to Inverter board via Power Supply board, but they are only related to display dimming and switching to power saving mode, in which cases front led still stays lit. This LCD can't be switched off by PC or its Main board when not in use for awhile - its design limitation, so front led is always lit, until Turn Off button is pressed on LCD.

[sambul83]

Re: Westinghouse L2410NM No Power, No LED

This thread is packed with valuable component and testing info, but sadly unfinished. I've the same Westinghouse L2410NM LCD with exact same boards as shown by jetadm123 with marked components through the thread, so wanted to continue here. I catch up a small bit on electronics repair lately thanks to this forum, so want to fix this one too and order parts for the last projects at once.

My monitor shown well described flickering problem for some time, but now it becomes unbearable. It starts flickering after a few hours of work 5-6 times in a row, stops for 1-2 hour, and then again. Each time screen gets black and audio is gone for a few sec, then restored and "HDMI" is shown in the upper corner. I noticed, its less flickering on a rainy day, and more under sun and light air movement.

Since audio is controlled by Main board, and backlight by inverter board, the only thing common for them is Power Supply board APO FP-120A01, so I assume this one has a problem, and it can be isolated to common connector pins for 2 other boards. As seen on the pics below, when dismounting the board, one wire fall out of connector. I don't know the connector's model and couldn't find section view, so just stripped, put the wire back and soldered on top. Did I do it right? Another thing, 2 pins on that connector were shot, I separated them.

Tested the LCD, and now suddenly front led is gone, and flickering stays the same. So either the wire can't be soldered to the connector's sit, or the 2 pins were bridged due to PCB conductive layer defect. Now back to square one... Can you guys give any suggestions, what component is most likely to cause flickering? And how to fix the front led problem now?

I'm kinda hesitant to replace all caps, since it may not be the culprit. Several folks in another thread did that only to face more serious issues with the LCD 6-month later. 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.

[nomoresonys]

Re: Westinghouse L2410NM No Power, No LED

good thread, NO FOLLOW UP by ben, but good info.

[Boregy]

Re: Westinghouse L2410NM No Power, No LED

how'd it go ben, did you get it working?

[jetadm123]

Re: Westinghouse L2410NM No Power, No LED

On pin 1 (VCC) of the TEA1522P, what voltage are you reading? Is it steady or fluctuating?

[PlainBill]

Re: Westinghouse L2410NM No Power, No LED

If you've already replaced it, it isn't necessary to replace it again unless you have a solid reason to suspect the replacement is defective.

• The solder joints look good on all of the caps and the polarity looks correct. I'll order a couple extra 100uF, 25V caps on my next Digi-Key order just to be sure though. I'm going to order a couple of the big filter caps as well since that's the only cap I haven't replaced.
• The part # on U4 is TEA15 2or3 with 2D62E107 underneath it. Difficult to read even with good lighting and a magnifying glass.
• I rechecked the diodes on the board and all seem to check out ok as shown in previous tests.
• I rechecked the resistors on the board and the all check out as good.
• I checked the MOSFETS and bridge rectifier as checked earlier and compared them to a known good power supply and they read almost exactly the same mounted on the board.

As an aside (unrelated to the above issue), I fixed another of my L2410NM power supply boards by replacing the main fuse and the large diode at D2. After initial capacitor replacement the board would power the monitor up for about 1 second, after which all power would blink out and the main power LED would go out. I close look at D2 showed that the diode must have gotten very warm at some point, because the underlying board was a little brown. I replaced the diode, added some artic silver compound on the MOSFETs, and reinstalled the heat sink. That monitor now works perfectly.

Curiouser and curiouser. A TEA1522P is a 14 pin SOT-14 integrated SMPS controller and power FET. Here's the datasheet.

PlainBill

[ben3843100]

Re: Westinghouse L2410NM No Power, No LED

It's more likely to be C23, 100uF, 25V. If you've already replaced it, it isn't necessary to replace it again unless you have a solid reason to suspect the replacement is defective.

A quick background on what happens at startup on these supplies. AC power is applied, the mains filter cap charges to full voltage (1.4 x line voltage). A low current path (bleeder resistor or constant current source in the SMPS controller) charges the Vcc filter cap to (usually) about 16V. At that point the SMPS controller starts.

The SMPS controller turns on the main power FET briefly, sending a surge of current through the primary if the transformer, causing pulses of current through the secondaries and a tertiary winding which provides Vcc for the SMPS controller. This is followed by additional pulses until the secondary voltage reaches the design value - usually 5 volts.

There are a few things that can stop this start-up cycle. If the Vcc filter cap is open, Vcc decays to below 10 volts and the process stops before the tertiary winding can provide enough voltage. An excessive load on the secondary will have the same effect. That can be a reversed cap, bad diodes, short on one of the loads, etc.

I'd have to see the part numbers of U2 and U4, but it appears to me that U4 is most likely the SMPS controller, mainly because of it's proximity to the opto-isolator.

PlainBill

If you've already replaced it, it isn't necessary to replace it again unless you have a solid reason to suspect the replacement is defective.

• The solder joints look good on all of the caps and the polarity looks correct. I'll order a couple extra 100uF, 25V caps on my next Digi-Key order just to be sure though. I'm going to order a couple of the big filter caps as well since that's the only cap I haven't replaced.
• The part # on U4 is TEA15 2or3 with 2D62E107 underneath it. Difficult to read even with good lighting and a magnifying glass.
• I rechecked the diodes on the board and all seem to check out ok as shown in previous tests.
• I rechecked the resistors on the board and the all check out as good.
• I checked the MOSFETS and bridge rectifier as checked earlier and compared them to a known good power supply and they read almost exactly the same mounted on the board.

As an aside (unrelated to the above issue), I fixed another of my L2410NM power supply boards by replacing the main fuse and the large diode at D2. After initial capacitor replacement the board would power the monitor up for about 1 second, after which all power would blink out and the main power LED would go out. I close look at D2 showed that the diode must have gotten very warm at some point, because the underlying board was a little brown. I replaced the diode, added some artic silver compound on the MOSFETs, and reinstalled the heat sink. That monitor now works perfectly.

[PlainBill]

Re: Westinghouse L2410NM No Power, No LED

Just to be clear, are you referring to the two small 22 uF 50V caps near the middle left of the board at position C22? I did initially replace all of the electrolytic caps on the board, but will replace these again if you think it's necessary. You mention the SMPS controller chip; is this the chip at position U2 on the back of the board?

It's more likely to be C23, 100uF, 25V. If you've already replaced it, it isn't necessary to replace it again unless you have a solid reason to suspect the replacement is defective.

A quick background on what happens at startup on these supplies. AC power is applied, the mains filter cap charges to full voltage (1.4 x line voltage). A low current path (bleeder resistor or constant current source in the SMPS controller) charges the Vcc filter cap to (usually) about 16V. At that point the SMPS controller starts.

The SMPS controller turns on the main power FET briefly, sending a surge of current through the primary if the transformer, causing pulses of current through the secondaries and a tertiary winding which provides Vcc for the SMPS controller. This is followed by additional pulses until the secondary voltage reaches the design value - usually 5 volts.

There are a few things that can stop this start-up cycle. If the Vcc filter cap is open, Vcc decays to below 10 volts and the process stops before the tertiary winding can provide enough voltage. An excessive load on the secondary will have the same effect. That can be a reversed cap, bad diodes, short on one of the loads, etc.

I'd have to see the part numbers of U2 and U4, but it appears to me that U4 is most likely the SMPS controller, mainly because of it's proximity to the opto-isolator.

PlainBill

[ben3843100]

Re: Westinghouse L2410NM No Power, No LED

I'd check for a shorted output diode. If they check out good, replace the small electrolytic caps near the SMPS controller chip (I believe you identified one of them as 100uF, 50V) and see if it works. If it now works, replace the rest of the electrolytic caps.

PlainBill

Just to be clear, are you referring to the two small 22 uF 50V caps near the middle left of the board at position C22? I did initially replace all of the electrolytic caps on the board, but will replace these again if you think it's necessary. You mention the SMPS controller chip; is this the chip at position U2 on the back of the board?

[PlainBill]

Re: Westinghouse L2410NM No Power, No LED

I've been away on businees for a bit, but have picked up this project again. In the mean time, I ordered new caps, as well as some spare fuses from DigiKey for this monitor, as well as some others I'm working on. This weekend I installed a known good power supply in this non-working monitor from one of my other working L2410NM panels and it powered on and displayed video fine, so I've now confirmed that there are no problems with the inverter or video board. I also suspected that I may have accidently blown the first 3.15 amp, 250V fuse on this power supply when testing, so I soldered in a new one.

• With the PS plugged in, I now show mains voltage of 169Vdc at the main filter capacitor with my meter set to 600Vdc.
• I still do not have any significant voltage at the logic or interter card pins.

Should I continue testing as kaboom mentioned, and test (or just replace) the diodes and FETs? Thanks.

I'd check for a shorted output diode. If they check out good, replace the small electrolytic caps near the SMPS controller chip (I believe you identified one of them as 100uF, 50V) and see if it works. If it now works, replace the rest of the electrolytic caps.

PlainBill

[ben3843100]

Re: Westinghouse L2410NM No Power, No LED

At this point you have a blown fuse and an unknown cause. The FET resistances were normal for in-circuit tests. (7K ohm does not sound like a short). I would hook a smallish (40 watt) light bulb across the blown fuse and apply power. If the light bulb glows brightly, you have a chance to determine what is drawing excessive current. If it glows dimly, Id replace the fuse, or use a larger light bulb as a substitute.

PlainBill

I've been away on businees for a bit, but have picked up this project again. In the mean time, I ordered new caps, as well as some spare fuses from DigiKey for this monitor, as well as some others I'm working on. This weekend I installed a known good power supply in this non-working monitor from one of my other working L2410NM panels and it powered on and displayed video fine, so I've now confirmed that there are no problems with the inverter or video board. I also suspected that I may have accidently blown the first 3.15 amp, 250V fuse on this power supply when testing, so I soldered in a new one.

• With the PS plugged in, I now show mains voltage of 169Vdc at the main filter capacitor with my meter set to 600Vdc.
• I still do not have any significant voltage at the logic or interter card pins.

Should I continue testing as kaboom mentioned, and test (or just replace) the diodes and FETs? Thanks.

[PlainBill]

Re: Westinghouse L2410NM No Power, No LED

The ohm reading confused me also, I think the key was that the reading were or the 20K scale so 13.68 and 17.3 would be 13.68 K ohms and 17.3K ohms.



I am of the automotive background so when I think of light bulb or test light , I think of using it in a parallel circuit for testing, Never thought of hooking up in a series circuit like a fuse.

It's amazing how creative you can get when you're trying to avoid blowing $10.00 worth of transistors.

Seriously, one of my favorite troubleshooting tools is a variac. It allows me to increase the input voltage very slowly while watching for any signs of problems. A light bulb makes a decent substitute.

PlainBill

[alexanna]

Re: Westinghouse L2410NM No Power, No LED

The ohm reading confused me also, I think the key was that the reading were or the 20K scale so 13.68 and 17.3 would be 13.68 K ohms and 17.3K ohms.



I am of the automotive background so when I think of light bulb or test light , I think of using it in a parallel circuit for testing, Never thought of hooking up in a series circuit like a fuse.