I have a HP L1940T LCD Monitor that doesn't power up & doesn't make any sounds. I looked at the circuit boards & I visibly see no signs of damage. I measured the voltage coming from the socket where the power cord is plugged in & it had the proper voltage. I do not no what to do next & would appreciate any help provided.
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Last edited by electrobe; 09-13-2012, 03:40 PM. -
Re: Hp l1940t no power
OK, I need in focused pictures of the bottom side of the board and the Main board again.
Chek the fuse (white cylinder), and then check the voltage on that large cap, be real careful since you will be working on the hot (line) side of the circuits.
Post picture in the using advanced, attachment function.Never stop learning
Basic LCD TV and Monitor troubleshooting guides.
http://www.badcaps.net/forum/showthr...956#post305956
Voltage Regulator (LDO) testing:
http://www.badcaps.net/forum/showthr...999#post300999
Inverter testing using old CFL:
http://www.badcaps.net/forum/showthr...er+testing+cfl
Tear down pictures : Hit the ">" Show Albums and stories" on the left side
http://s807.photobucket.com/user/budm/library/
TV Factory reset codes listing:
http://www.badcaps.net/forum/showthread.php?t=24809 -
Re: Hp l1940t no power
Here are more photos for you. Let me know if you need more. I will check the fuse.Attached FilesComment
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Re: Hp l1940t no power
I tested the large ELCAP 100UF M 450V as you have suggested & the DC voltage was 171.7 Volts. The 3.15A 250 vac fuse when I set my multimeter to ohms read 000.0Comment
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Re: Hp l1940t no power
Fuse and voltage across cap look good. I know you said the monitor doesn't power up, but you do get any activity from the power LED on the front panel?Comment
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Re: Hp l1940t no power
What are the DC voltages on all the pins of connector CN951?--- begin sig file ---
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Re: Hp l1940t no power
There is no activity on the LED front panel. I checked the DC voltage all the pins of connector CN951 and I got 2.92V on pins 6 & 7, 0.012V on pins 3 & 4. When i measured a 2nd, 3rd & 4th time I got the results of 0000 across all pins.Comment
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Re: Hp l1940t no power
Try measuring the voltage across the small cap c927 located in the middle of the power board.Comment
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Re: Hp l1940t no power
This a service manual that matches your chassis.Never stop learning
Basic LCD TV and Monitor troubleshooting guides.
http://www.badcaps.net/forum/showthr...956#post305956
Voltage Regulator (LDO) testing:
http://www.badcaps.net/forum/showthr...999#post300999
Inverter testing using old CFL:
http://www.badcaps.net/forum/showthr...er+testing+cfl
Tear down pictures : Hit the ">" Show Albums and stories" on the left side
http://s807.photobucket.com/user/budm/library/
TV Factory reset codes listing:
http://www.badcaps.net/forum/showthread.php?t=24809Comment
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Re: Hp l1940t no power
I went back and measured the small cap c927 located in the middle of the power board and I got a result of over voltage 0.L. Thanks to Budm providing the service manual I also measured the voltage for the pin8 of IC901 and got a result of 0.L over voltage. Does this mean my board is toast?Comment
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Re: Hp l1940t no power
Please recheck the batteries in your meter and also try measuring something like a AA batteries or a 9-Volt batteries. It looks like the power supply not siwtching, need to do more components testing, but let's verify the meter first.Never stop learning
Basic LCD TV and Monitor troubleshooting guides.
http://www.badcaps.net/forum/showthr...956#post305956
Voltage Regulator (LDO) testing:
http://www.badcaps.net/forum/showthr...999#post300999
Inverter testing using old CFL:
http://www.badcaps.net/forum/showthr...er+testing+cfl
Tear down pictures : Hit the ">" Show Albums and stories" on the left side
http://s807.photobucket.com/user/budm/library/
TV Factory reset codes listing:
http://www.badcaps.net/forum/showthread.php?t=24809Comment
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Re: Hp l1940t no power
I did as you had ask & checked a AA battery to make sure the meter was working properly and it was.Comment
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Re: Hp l1940t no power
Post a picture of your multimeter. 0L implies you are likely using an autoranging multimeter. For it to display 0L, the voltage would have to be over 1000V DC.
Most manual range multimeters show a "1" on the left hand side to signify out of range.--- begin sig file ---
If you are new to this forum, we can help a lot more if you please post clear focused pictures (max resolution 2000x2000 and 2MB) of your boards using the manage attachments button so they are hosted here. Information and picture clarity compositions should look like this post.
We respectfully ask that you make some time and effort to read some of the guides available for basic troubleshooting. After you have read through them, then ask clarification questions or report your findings.
Please do not post inline and offsite as they slow down the loading of pages.
--- end sig file ---Comment
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Re: Hp l1940t no power
Here is the photo of my auto ranging multimeter that you have requested. I will go back & retest c927 & voltage for the pin8 of IC901.Attached FilesComment
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Re: Hp l1940t no power
I went & remeasured C927 (results 0004 V) (which is a 68uF 25V capacitor) & IC901 pin8 (results 0162V). The capacitors on this board are from the manufacturer Elite. I removed the decimal in my auto range multimeter.Comment
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Re: Hp l1940t no power
Retiredcaps is more an expert on meters than I am, but since you indicated no decimal points in your readings, it appears that the meter is set to too many signifcant digits. In other words, pin 8 should show 162.XX Vdc and C927 something like 4.XX Vdc.
4 volts across C927 is too low a start voltage for IC901. You need a minimum of 10V. I would try changing C927 to see what happens.Comment
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Re: Hp l1940t no power
I finally had a chance to get back to the power board & replace C927 with a new one & remeasured the voltage. It jumps back & forth from 9V to 10.40V. I have no clue where to go from here. I would appreciate any input that could be provided.Comment
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--- begin sig file ---
If you are new to this forum, we can help a lot more if you please post clear focused pictures (max resolution 2000x2000 and 2MB) of your boards using the manage attachments button so they are hosted here. Information and picture clarity compositions should look like this post.
We respectfully ask that you make some time and effort to read some of the guides available for basic troubleshooting. After you have read through them, then ask clarification questions or report your findings.
Please do not post inline and offsite as they slow down the loading of pages.
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Re: Hp l1940t no power
Yes the voltage still fluctuates when tested.Comment
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Re: Hp l1940t no power
Follow the steps on page 21 using budm's pdf file.--- begin sig file ---
If you are new to this forum, we can help a lot more if you please post clear focused pictures (max resolution 2000x2000 and 2MB) of your boards using the manage attachments button so they are hosted here. Information and picture clarity compositions should look like this post.
We respectfully ask that you make some time and effort to read some of the guides available for basic troubleshooting. After you have read through them, then ask clarification questions or report your findings.
Please do not post inline and offsite as they slow down the loading of pages.
--- end sig file ---Comment
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Greetings to all, I hope you are well.
I consult you because I have a problem with this power source.
The TV when it is connected to the electrical power turns on the blue light but does not give an image. the source is heard a hum.
When I disconnect the power from the TV plates and power it up by itself, the hum goes away.
I have the STB voltages of 5vdc. The microcontroller is powered with said voltage and the main board LED lights up.
but not the 12v or 17v ones, nor the 300vdc high voltage voltages, nor the VS or VA....06-20-2023, 04:30 AM
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