I am having problems diagnosing the error with a notebook LCD display inverter.

Symptoms: After switching the notebook on, the LCD backlight comes on but the intensity oscillates rapidly (flickers). After about 1 second the backlight turns off completely. Once the backlight has turned off, the AC output of the inverter measured with a DVM is 0 Vac.

I visually checked the inverter board and there are no obvious faults.

Given the symptoms, can anybody venture a guess at the problem?

  • On the one hand I am tempted to say that the backlight is ok (after all it ignites) and the problem is more likely to lie with the inverter.
  • On the other hand I am wondering whether the flickering of the bulb (faulty bulb?) causes a open-circuit protection of the inverter to kick in after 1 second.

So in summary I am not quite sure whether the fault is more likely to lie with the bulb or the inverter.

  • 1
    \$\begingroup\$ Is the backlight a cold cathode fluorescent tube (CCFT)? \$\endgroup\$ – JYelton Jan 2 '13 at 20:26
  • \$\begingroup\$ @JYelton I believe so but have not taken everything apart. CCFT is the standard for LCD notebook backlights however, no? \$\endgroup\$ – ARF Jan 2 '13 at 20:39
  • \$\begingroup\$ Repair questions are off-topic. \$\endgroup\$ – Leon Heller Jan 2 '13 at 20:44
  • 1
    \$\begingroup\$ @LeonHeller Point taken. I have remove the repair component from the question and focused on the fault diagnosis procedure to make the question and its answers transferable to other situations with LCD backlight issues. \$\endgroup\$ – ARF Jan 2 '13 at 20:51
  • \$\begingroup\$ @Arik Not necessarily, there's also LED backlights, but they wouldn't require an inverter. \$\endgroup\$ – JYelton Jan 2 '13 at 20:56

Just be aware that there are potentially very high voltages on board the inverter. Be careful.

It is entirely possible that you'll be able to find a replacement part from another laptop. There are a few common suppliers that multiple manufacturers used. Look to a laptop supply place in your area for leads and supplies. Here I am referring to both the CCFL and the inverter.

| improve this answer | |
  • \$\begingroup\$ Thanks for the warning about the high voltage. It is one of the reason why my fault-finding efforts were fairly rudimentary. I did not want to fry my DVM... Regarding replacement: Sumida is a very common supplier. My primary concern is that I do not know to what extent voltages and current requirements of backlights in different laptops are comparable. Also, as already mentioned, there is the issue of the 4 IO(?) pins. \$\endgroup\$ – ARF Jan 2 '13 at 20:43
  • \$\begingroup\$ @Arik You may want to look for a similar or exact model laptop with a cracked screen or dead motherboard, and see if you can extract working backlight parts from it. \$\endgroup\$ – JYelton Jan 2 '13 at 20:57
  • \$\begingroup\$ @JYelton Good idea, unfortunately it is a rare model (about 1 on Ebay worldwide every few months). Maybe I will get lucky... \$\endgroup\$ – ARF Jan 2 '13 at 22:53
  • \$\begingroup\$ +1 for the suggestion to replacement. It's called fault isolation method in troubleshooting. However this could not be a final accepted answer. Because I mean it's all about symptoms and root cases. \$\endgroup\$ – Standard Sandun Sep 30 '13 at 10:34
  • \$\begingroup\$ Most probably this is due to electronic dieseling issue. I'm not aware of this, but electriciantalk.com/f2/… \$\endgroup\$ – Standard Sandun Sep 30 '13 at 10:50

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.