Lenovo Pro2840mD monitors power down after a while

[EvilDeece]

I'm good, these 2 no longer boot, so there's not much point putting more effort into them for me.

They're a lot cheaper from China, AliExpress has them for <$10 for 5 pieces: https://a.aliexpress.com/_mqB1Ty5

I suspect I overheated the chips with my crude reflow setup (hot air gun), but I'm not sad, these were already slated for e-waste.

[tonycrouch]

I’m hearing ya mate - top work giving it a go. 👍

[Pctronics]

I thought I’d share my supposed fix for this. All 3 chips were reflowed ramp up temperature of 120c stage 2, 180c @2mims stage 3, 280c @1min stage 4 @400c @30seconds ramp down stage 1 280c 2mins stage 2 120c @1mins. Bit of a weird ramp but it was based on the flux bubble activity. I used amtec NC-559-V2-TF and did not clean it off. While still warm I added general thermal paste and let it sit in drier for a few hours. The thermal paste was enough to keep the heat sink sticky to the chips. Reassembled the unit and low and behold it hasn’t shut down after streaming OBS and I’ve been testing it for the last week. I couldn’t even get 15mims out of it without it powering down. And now I’ve saved $400aud and don’t have to buy a new monitor.

[EvilDeece]

That's good to hear - what did you use to reflow it? An SMD oven or a rework setup?

[Pctronics]

although I do have a reflow oven this board is too big, I just used my hakko rework station. I rigged it to a microphone stand so I don't have to hold the handset. I also use aluminium cans and a little captan tape to make mini chambers around the chip/work area to direct the heat more effectively. I use the same method when removing GPU/CPU and it works really well.

[EvilDeece]

Ah, thanks. I've been thinking of attaching my rework gun to a scissor arm to do similar, after seeing the combined IR heater + rework stations in action. Time to go and 3D print a mount, I guess

[perieanuo]

I thought I’d share my supposed fix for this. All 3 chips were reflowed ramp up temperature of 120c stage 2, 180c @2mims stage 3, 280c @1min stage 4 @400c @30seconds ramp down stage 1 280c 2mins stage 2 120c @1mins. Bit of a weird ramp but it was based on the flux bubble activity. I used amtec NC-559-V2-TF and did not clean it off. While still warm I added general thermal paste and let it sit in drier for a few hours. The thermal paste was enough to keep the heat sink sticky to the chips. Reassembled the unit and low and behold it hasn’t shut down after streaming OBS and I’ve been testing it for the last week. I couldn’t even get 15mims out of it without it powering down. And now I’ve saved $400aud and don’t have to buy a new monitor.

you're lucky, 400C is a bit much for the peak
but 400C with airgun is much less below chip, depends on your airflow setting
I never had more than 300-330C on metcal 5000, and the temp was the real temp of the chip, we had thermocouples on top/bottom side of pcb. the air flow and heating power is gigantic for those machines comparing with airgun. of course, it was solder without pb, the laptop/desktop nvidia cards sh...ty years rememberings
I tried for some pcb's up to 400C, the result was a dead or semi-dead video chip
good work, you have 'good hand'

[chilobo]

I own a Lenovo 2940. Since about one year my monitor about once a week makes a short knacking noise, goes dark, but comes up again after about 3-5 seconds.
I suspect some caps are bad, thinking about replacing them.
But: How do I open the monitor? There seem to be no screws. Do you have to pry the casing open with some plastic tools? Where do I start?

[EvilDeece]

The 2840 had clips around the edge of the frame, use a plastic pry tool, guitar picks, or credit cards to separate the catches without damaging the case.

[transistor-man]

Hi all, I came up with a pretty simple workaround to get these lenovo's running, I documented it here: https://transistor-man.com/lenovo_4k_repair_update.html

I found just having some air making its way through the back of the case would keep the temps down enough to prevent the thermal issue with the graphics processor part. I realize it's a bit goofy but it works.

Cad files for printing are included in the writeup