I tried with another just marked '1838' and with a 1K and a LED as pullup. The other had 10K. and no led.
Then it looks like this:
Decoded NEC: FF02FD (32 bits)
Raw (68): 9050 -4450 650 -550 650 -550 650 -550 650 -550 650 -550 650 -550 650 -550 650 -550 650 -1600 600 -1700 600 -1700 600 -1700 650 -1600 600 -1700 600 -1700 650 -1650 600 -600 650 -550 650 -550 650 -550 650 -550 650 -550 650 -1600 600 -600 650 -1600 600 -1700 600 -1700 600 -1700 650 -1600 600 -1700 600 -600 650 -1600 600
Now decoded as NEC, and all buttons start with "FF".
Raw, equal to the other, but a slight change in timing.
I try to wire it to run 5V...