Humax 40″ LCD TV repair

Introduction

I was taking a walk with my girlfriend when we came by a house with a 40″ LCD TV standing against the wall outside, on our way back to the apartment the TV was still standing there. I knocked on the door and asked if I could take it if it was just for the trash. I got it for free and they spared themselves a trip to the recycle station.

Dragging the 38 Kilogram heavy TV home was a less pleasant part of this great deal

 

Safety

WARNING!: Working with electricity is dangerous, all information found on my site is for educational purpose and I accept no responsibility for others actions using the information found on this site.

Read this document about safety! http://www.pupman.com/safety.htm

What to look for

I turned the TV on and got a picture with no signal noise, but the back light was flickering at about 10 Hz making the picture absolutely useless to watch.

Taking the TV apart was no problem, just some few 30 screws around the frame and we are inside to view a main board and a power supply board.

Previous knowledge tells me that if there is a picture, noise or not, on the screen, the main board is okay. Looking at the power supply board it quickly became clear where the problem was to be found. 3 clearly popped CapXcon capacitors is likely to be the fault.

The red circles on the above picture shows where the three capacitors were located. The two large capacitors are the smoothing capacitors for the 24VDC supply to the back light inverter boards, these were measured to only 300uF capacity. The reduced capacity to around 1/5 of the original explains the ripple current in the 24VDC supply that makes the inverter boards emptying them before the power supply board can charge the capacitors. Thus making the back light flicker.

I found some 2200uF capacitors that I de-soldered from other electronics to replace the popped CapXcon capacitors, turning the TV on revealed that it was fixed and now able to show a steady picture.

All I used was some common electronics knowledge, a soldering iron and 3 capacitors that I had from other old electronics.

Bottom line: I got a free 40″ Humax LDE-40A LCD TV and spent about an hour repairing it.

9 Responses to Humax 40″ LCD TV repair

  1. Pingback: How to repair a LCD TV | Kaizer Power Electronics

  2. MicaH says:

    I have the same model tv and my backlight caved in as well. I came across this site, opened up my tv and voilá! Three popped caps! I’ll get some repair parts tomorrow and start soldering. I’ll let you know how it turns out. Thanx 4 sharing!

  3. Abdul Ladak says:

    Exactly the same problem…opened it up and there they were… the three popped caps….just need to find a soldering iron now (haven’t used one in over 30 years!!!).

    Thanks for documenting this with the photographs…saved me a lot of money.

    The remote control receiver also stopped working on this telly about a year ago….any ideas??

  4. Patrick says:

    Hi there! Thanks for sharing this information… I’ve got the same make/model TV witch broke down on me this week. At first i wanted to drop it of at a repair shop…but becouse of its weight in combination with some very steep vleet of narow stairs, i decided to look in to it my self…
    And after some Googeling i ended up here…And indeed, the same problem over here…

    Big thanks from the Netherlands!

  5. shaun says:

    Hi
    How do you tell if the 3 capacitors have popped?

  6. MicaH says:

    Either the capacitors are completely sprung or the top is bulged. My repair worked perfectly, by the way.

  7. Pingback: test lcd tv backlight inverter | Elektronik Nyheder

  8. Todd Bennett says:

    Hi, when you say the Mainboard is ok when there is a picture, do you also mean that if the splashscreen comes up for 5 seconds but switches off this means the Mainboard is probably still good ?
    Is it possible to check the inverter boards out of circuit?

  9. Mads Barnkob says:

    Hi Todd

    If you can get a stable, right colours etc splash screen, then the processor and output circuitry is still good, but the signal input could be damaged if you do not get a picture there.

    You might need to find some turn on pins on the power supply board itself to turn it on, some are made to only turn on the backlight if there is a mainboard connected to it.

    Kind regards
    Mads

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