A couple of month ago I started to get problems with my ThinkPad T410 stopping playing sound through the speakers after a couple of minutes but still would work with my earphones without problems.
I then found out that I can get them back on by running:
sudo hda-verb /dev/snd/hwC0D0 0x1f SET_POWER_STATE 0
which changes the power state to on again, so I did put that into a script and made a custon keyboard shortcut on F9 to get my sound back. Sadly the sound got only back for a short time and the time span got shorter and shorter.
So I searched more and after a long time I found out that someone who had the same problem with a different ThinkPad put a passive heat sink on the sound chip and the problem went away.
I found some passive heat sinks at our local electronics store which were advertised for the Raspberry Pi. I got them and opened my ThinkPad just to see that the sound card didn't look like the one the person linked and I couldn't find out which of all the chips was the audio chip on my motherboard.
Back to the search engine, and after some time I found a German blog which describes the same problem as I have and how to fix it on a T510 instead. But happily the guy wrote a lot and also mentioned the name of the sound chip, which is from Conexant and is called CX20585-11Z.
With this information I was able to find a Lenovo ThinkPad T410 Notebook Computer Teardown which has photos of the motherboard and points out what every chip is called. This way I found it on the bottom side of the motherboard, finally!
I put the small passive heat sink on it and run a test run, sadly no change, after a couple of minutes still the sound was gone. But the German guy put a big metal plate in there as the heat sink there so I still might have a chance with something bigger. When I touched the chip while running it was still really hot.
I took the bigger one and because I lacked a metal plate I took a beer can, cut and folded it once and put it in between the heat sink and the bottom plastic. Because I don't have a optical drive I had a lot of space nearby to put my new big aluminum plate to take away the heat from the chip and the heat sink passively.
Now I run it for more than an hour in full volume and every thing seems to work fine again!
I'm really happy to have gotten such an awesome laptop to be able to learn a lot about electronics with it. It is already 6 years old so I don't feel that once I break something it will be a big deal.