Westinghouse L2046nv

[jetadm123]

Re: Westinghouse L2046nv

With Q102 shorted, it could have taken out other components. Please post a good focused photo of the bottom of the power board. I'm also concerned that the startup cap, CE107, is not charging from the the pwm chip U104 (located bottom side on power board) pin 6, since you said you measured 0V across it, possibly indicating U104 is also bad.

[Shredasaurus]

Re: Westinghouse L2046nv

I still recommend changing out ALL the Capxon caps on the power board.

I swapped all of the caps except for the large cap with Rubycon caps.

With Q102 shorted, it could have taken out other components. Please post a good focused photo of the bottom of the power board. I'm also concerned that the startup cap, CE107, is not charging from the the pwm chip U104 (located bottom side on power board) pin 6, since you said you measured 0V across it, possibly indicating U104 is also bad.

I am attaching the best photo I could get of the underside. I am slightly embarrassed because I do my best to be careful and I should know better but I accidentally grounded my test probe when I was initially testing for 110v coming in on the trace. The spot is pretty obvious in the photo. Not having a replacement fuse immediately on hand, I soldered in a jumper. I know this is not really a good practice or in most cases not the best idea at all. I will be ordering a replacement with any other components from DigiKey. Can someone help me select an appropriate replacement? I attached a photo of it as well.

What should I look at next?

Thanks, you guys have been great help so far.

[retiredcaps]

Re: Westinghouse L2046nv

Can someone help me select an appropriate replacement?

1) I believe this is the correct one. Check the dimensions to make sure it fits.

http://search.digikey.com/us/en/prod...1181-ND/809325

2) Clean up the black marks of the backside with some isopropyl alcohol.

3) There are 3 SMD resistors (R136, R137, and ???) just NW of the AC plug. Measure them in circuit to see if the resistance readings matches their markings.

4) Clearly jetadm123 has worked on this board because he identified U104 without a picture of the backside. I have no such knowledge so what is the part number for U104?

For U104, find its datasheet. Then find the pins that are VCC and GND. Measure the resistance between those two pins. Any reading less than 30 ohms suggests U104 might be bad.

5) From the photo, it also looks like U104 has some black marks?? Is that IC physically damaged (cracked, split, bubbled, etc)?

[jetadm123]

Re: Westinghouse L2046nv

Yes, I have worked on this board before. It seems that this board was widely used on Westinghouse on Acer monitors. One of the boards I worked on had similar issues to yours. In addition to retiredcaps suggestions, check resistors R131,132,133 and 134 (located above U104) to see if they're open/shorted.

[Shredasaurus]

Re: Westinghouse L2046nv

3) There are 3 SMD resistors (R136, R137, and ???) just NW of the AC plug. Measure them in circuit to see if the resistance readings matches their markings.

Ok we have R136, R137 and R138 they all have 3903 printed on the top of them. I google searched Resistor 3903 and 390K ohm resistors kept showing up. I don't know if this is the correct value though? I tested each one with my Multimeter set to 20M ohm. They all give a reading of .39 which I believe is correct if they are in fact 390K ohm Resistors?

For U104, find its datasheet. Then find the pins that are VCC and GND. Measure the resistance between those two pins. Any reading less than 30 ohms suggests U104 might be bad.

5) From the photo, it also looks like U104 has some black marks?? Is that IC physically damaged (cracked, split, bubbled, etc)?

U104 does look like it has some black on the metal in the center but I don't see any cracks or bubbling. There doesn't appear to be any markings on it to identify the part #?

check resistors R131,132,133 and 134

on 20M scale R131 reads .18
on 20M scale R132 reads .18

I can't get a reading on 133 or 134 on any scale on my meter except OL.

Thanks!

[retiredcaps]

Re: Westinghouse L2046nv

I google searched Resistor 3903 and 390K ohm resistors kept showing up.

3903 (last digit tells you how many zeros) is 390,000 or 390K.

They all give a reading of .39 which I believe is correct if they are in fact 390K ohm Resistors?

.39, move the decimal 3 places to the right and we get 390K. Correct.

on 20M scale R131 reads .18
on 20M scale R132 reads .18

I can't get a reading on 133 or 134 on any scale on my meter except OL.

What are the markings on the above?

[selldoor]

Re: Westinghouse L2046nv

Hi I have found a schematic which I believe relates to this board.



BUT cannot upload it - is the site where it is based banned?
seems within the size parameters

[Shredasaurus]

Re: Westinghouse L2046nv

Thanks Selldoor!

What are the markings on the above?

I can't read them because they appear to be slightly burned on the top. According to the parts list that Selldoor just posted

R131-R134 should be Res SMD 1/4w , 200Mohm, F 1206

-------------------------------------------------------------
I followed the pin out of U104 in the schematic on page 10 of the same file. The only setting I get a reading on for Vcc and Ground is 200Mohm. I believe I am on the right pins according to the diagram but my Meter behaves odd. It starts around 60 and slowly counts all the way up to 200. I could still be on the wrong pins though.....U104 isn't oriented the same direction as I see it on this Schematic. Any ideas?

Thanks

[retiredcaps]

Re: Westinghouse L2046nv

Post a picture of your multimeter.

[retiredcaps]

Re: Westinghouse L2046nv

R131-R134 should be Res SMD 1/4w , 200Mohm, F 1206

I looked at the pdf and it says 200mohm. There is a huge difference between milli and mega.

Another part in the pdf shows 1Mohm so there is distinction between the two.

I suspect your resistor is 0.2 ohms. My Fluke 75 only reads up to 40M ohm so it is highly unlikely a 200M ohm resistor.

Retest with your multimeter set on the 200 (two hundred) ohm scale.

[jetadm123]

Re: Westinghouse L2046nv

R133 and R134 are 0.2 ohm resistors connected in parallel, which should give you approx. 0.1 ohms. If the resistors show signs of severe overheating (as evident by the the burned off markings) then I would consider replacing them.

I think you reporting your readings on the 20Mohm (20 Meg Ohm) scale is adding confusion as reading 0.2 ohms on that scale would be difficult. Did you mean milliohm? There's a BIG difference between the two.

If you're getting only a reading on milliohm scale between vcc and ground on U104, then that indicates a short.

[Shredasaurus]

Re: Westinghouse L2046nv

Post a picture of your multimeter.

Ok here ya go.

Retest with your multimeter set on the 200 (two hundred) ohm scale.

Getting nothing on any of the four resistors in question.

If you're getting only a reading on milliohm scale between vcc and ground on U104, then that indicates a short.

I still am not exactly sure which pins are which because it is oriented differently from the schematic.

What would be considered a "good" reading between Vcc and Ground?

Thanks

[retiredcaps]

Re: Westinghouse L2046nv

Getting nothing on any of the four resistors in question.

1) By "nothing", do you mean "1" on the left hand side of display?

2) Touch the two probes together with your multimeter set on 200 ohms. It should read 1.0 ohms or less. What do you get?

3) Now remeasure the resistors. If you get "1" on the left hand side of the multimeter, that indicates that the resistance is greater than 201 ohms. This means that your 4 resistors are likely all bad.

4) There is a chance because all boards are different with the various revisions, that those 4 resistors are not 200 milliohm resistors. To verify, we need a clear focused picture of just those 4 resistors. Try to clean them up with isopropyl alcohol and get some good lighting for the camera.

What would be considered a "good" reading between Vcc and Ground?

5) A shorted (bad) reading is something 30 ohms or less.

6) See the attached diagram. See the notch? Pin 1 is below the notch. Then the pins are numbered counterclockwise.