Reality check needed - do two things go faulty at the same time?

[sorcerer]

Client brings in a laptop with no display on screen. It works when connected to an external monitor/TV so I know the graphics card is OK.

I fire it up, shine a torch (flashlight) at the screen and see a very dim display, so first thought is the screen inverter. I have a known good CCFL so I plug it into the inverter and it fails to light, thereby confirming my diagnosis. New inverter arrived this afternoon so I connect everything up - and still only a very dim display on screen. Thinking the new inverter may be faulty I plug in my 'test' CCFL and it lights up as it should!

So to summarize, old inverter does NOT light up my test CCFL, the new one DOES - but neither inverter lights up the screen. Am I just unlucky in having a faulty inverter AND faulty screen at the same time, or am I doing something wrong? This is on a Toshiba Equium U400-146 (PSU42E) by the way.

 

[NYJimbo]

Its actually quite common for the inverter and the CCFL to be faulty at the same time. The last test would be to try to light the CCFL in the LCD. This would require some outside source of power, like a tester. If it lights then you are back to square one, but if its dead then yes you have two failures.

Its like that with DC jack repair. When the DC jack starts to go the customer starts wiggling the DC plug from the AC adapter. It works for a while until either the DC jack fails completely OR the DC plug from the adapter fails. Many times I replace a DC jack but the customer does not bring in the adapter/charger for me to test. Sometimes they go home and they have the "same problem". But what it ends up is a bad AC adapter and they have to replace that as well.

Its like its very common to find a secondary fault when replacing a broken LCD screen. Most of the time when they break the LCD its from a crush or a drop, that can cause HD failures or something to go loose inside the laptop.

So yes, its common for two things to fail at the same time.

 

[sorcerer]

Cheers Jimbo, nice to know I'm not going daft. I'll try to test the CCFL in the LCD next, as you suggest.

 

[JustInspired]

P.S. you can get one of those cheap case lighting kits for testing tubes. They normally come with a double inverter in a plastic enclosure that gets its D.C. power from a molex connector. We use both the kit‘s inverter and CCFL tubes separately for testing backlights and inverters.
We also have a few broken screens around for testing inverters.

 

[sorcerer]

P.S. you can get one of those cheap case lighting kits for testing tubes. They normally come with a double inverter in a plastic enclosure that gets its D.C. power from a molex connector. We use both the kit‘s inverter and CCFL tubes separately for testing backlights and inverters.
We also have a few broken screens around for testing inverters.

Cheers my friend - just been to buy one of those kits this morning

 

[Kitten Kong]

I've had similar issues in the past. Screen being dim, diagnosed inverter. Order and install the inverter, only to find its the screen also.

So your not alone buddy .

My procedure now with inverter diagnostics, is to put a known good lcd screen in the machine as well to double check. Only takes a couple of extra minutes, and well worth the time taken.

 

[sorcerer]

Glad to know I'm not alone Nige

Turns out that the screen is indeed faulty as well, so thanks everyone