Weird noise on screen T41

[racerx]

I have a t41, I have replaced the motherboard, GPU and the LCD inverter.

However I get this flickering noise on the screen, it is hard to explain, but it sometimes starts as parts of the screen where the a window is being displayed has this interference, a bit like noise you get from TV that has no signal, but with the rest of the screen looking ok. It then progresses to the whole screen at times, making it unusualable. When I replaced the inverter it went a way for a few minutes, and then it stopped after a removed and replaced the inverter (same one).

The laptop was fine for an hour, but now is has come back, could the cause be the LCD cable? Given that I have replaced the motherboard, gp, and inverter? Is there a way to shield the cable etc? Its the SXGA type for a t41

[poshgeordie]

Welcome to the forums.

Does it still have this noise when running on battery only with the AC Adapter disconnected?

Is the AC Adapter an official IBM one or an aftermarket one?

What happens if you connect an external display?

[racerx]

Welcome to the forums.

Does it still have this noise when running on battery only with the AC Adapter disconnected?

Is the AC Adapter an official IBM one or an aftermarket one?

What happens if you connect an external display?

it has the noise with or with out the ac adapter, which is an offical IBM one.

It now only seems to do to it intermitantly now, but I suspect it has something do with changing ACPI states.
I wonder if the CPU itself could be bad?, in that when it goes through different power states it produces noise that shows up on the screen.

I have tried plugging in an external monitor when the noise appears, the noise disappeared from both screens...

[poshgeordie]

I'm linking my reply with the other similar topic thinkpads.com/forum/=102112, T43 Sizzling & noises on LHS.

It's revealing that the noise disappears from both screens. I'm wondering if there's a smoothing capacitor beginning to leak or not filtering a supply line properly.

OR - whether there's a smoothing inductor which is "singing". Inductors are those square black components and consist of a coil of wire around a carbon-like former, and works to reduce any supply line interference.

As the supply voltage currents change, if either of these components are tending towards working less than perfectly, then their "effectiveness" will change as the currents, and amount of interferrence on those lines, change (sorry terrible sentence but hope you get the idea).

Regarding then trying to fault find it, it's almost impossible unless there are any physical signs of component damage.

I'm from Newcastle and would be interested in looking at your noise. PM me if I can help.

[racerx]

I have a picture of the noise

One of the things that is quite strange, is that when it does start happening if I move a window on the screen around quickly the noise can go away, or get worse, almost in response to the different voltage load on the system.

Give that I have all ready replaced the system board (with its GPU), the inverter, and it is not the AC power supply, how could I replace these smoothing capacitors? or are they on the system board, and thus I have replaced them once before?

Perhaps I will try and get an SXGA cable and see if that does the trick.

[poshgeordie]

Thanks for the picture.

To summarise:-
1. You've replaced the motherboard & inverter.
2. It is still noisy when working on Battery only with the AC Adapter removed.
3. The noise disappears when an external monitor is plugged in.

What you've not done:-
1. Not replaced the screen or LCD Cable, but you've replaced the inverter.
2. Not changed the CPU or RAM modules.

One significant fact is the noise disappearing when an external monitor plugged in. An ext monitor will provide a good earth path from the Thinkpad, and hence a good grounding path to get rid of any noise within the Thinkpad.

Things to Try:-
1. Another known working complete screen assembly
2. Another CPU and RAM module.
3. Remove the Hard Drive,run TP from Ubuntu 10.10 Live CD in CD/DVD drive - eliminates possibility of noise from HDD.

It's not practical to change the capacitors - I only suggested it as being a possible problem area.

Really weird - I'd love to get my hands on this to see if I can find it - feel free to PM me......

[racerx]

Its not the hard disk, and I can test the ram, as it has two banks of chips.

I have ordered a new cpu and cable of ebay, so fingers crossed. I keep you posted.

Thanks very much for the assistance!