I haven't seen this particular situation on the discussion. I have an older Vizio TV without a HDMI port. I have a Roku Express and bought a HDMI to RCA adapter and hooked them up. The Roku light is on, the TV is on, and I think I found the correct input (AV3). Last night the Roku icon showed up when I was working on it and I was able to get through part of the setup, and then it went blank. I unplugged the Roku and tried it again and the Roku symbol shows briefly and then disappears. Any ideas?
It's next to impossible to buy a new streaming player from any manufacturer with analog outputs any longer. The Roku Express+ 3910 was the last one Roku offered, and it was discontinued in 2019.
It's difficult to determine why your setup isn't working. I'd first try the Roku on a TV with HDMI, just to make sure it's still working. It's possible the Roku has died, or it simply may not like the analog converter you are using. But it seems likely the problem is with the converter. I think that because it sounds like you are briefly getting a video signal, then the lock is lost.
The initial bouncing letter startup screen is in the lowest resolution the Roku supports, 720p, but when it goes to the Roku home page it switches to a higher resolution agreed upon between the Roku and the TV during their initial HDMI "handshake" information exchange.
My guess is the Roku is trying to send its signal to the TV in a resolution the TV cannot handle. Perhaps your HDMI to RCA adapter is interfering with the handshake exchange, or maybe the TV with no HDMI port doesn't receive or know how to respond to the Roku's HDMI handshake request in the first place.
If you can temporarily connect to a TV that DOES have an HDMI port, set Settings > Display Type to 720p or the actual resolution of the old TV if you know it, rather than Auto detect, and see if that enables it to work on that old set.
If all else fails, you can try to adjust the Settings > Display type setting when you can't see the screen. After booting up the Roku and getting past the bouncing letters startup display:
A• Press the remote Home button 2 times (Makes sure you're on the home screen at correct position with no screen saver running)
B• Up (Go to Settings)
C• OK or Right (Go into Settings options)
D• Down 3 times (Highlight Display type. It passes through Theme on the way and this may take a few seconds before moving on) so wait 30 seconds or so before continuing.
D• OK (Chooses Display Type option)
F• Up (Moves off current Display Type setting to next one up)
G• OK (Selects this Display Type setting)
At this point, the Roku will try to use the selected Display Type setting. The TV may take a few seconds to adjust to this new setting.
If you see a picture, click the "Yes, looks good" button to lock in this setting.
If you don't see anything, wait about 15 seconds, then hit OK to click the unseen default "No, there's a problem" button to return you to the menu.
H• If you have not found a resolution setting that works, repeat steps F and G to try the next Display option. Repeat until you find one that works.
Also, make sure to check the basics, like these converters often have a switch to select PAL or NTSC, and that needs to be NTSC if you’re in the US. You might expect that if the logo comes through, then it must be OK, but NTSC TVs often give weird partial functionality when they are fed PAL.