Well, Rene, this is about 3 years late frm your request, but I just got a TW-4100.
The good news is that allelectronics.com has what appears to be an EXACT replacement for the display lamps in the TW-4100 radio.
I used this one:http://www.allelectronics.com/cgi-bin/category.cgi?item=LP-6
I have this one, but it is not as direct. I think that it would last longer, but would be dimmer.http://www.allelectronics.com/cgi-bin/category.cgi?item=LP-7218
I also replaced the backup battery. This all took about 1.5 hours start to radio back together.
open the case (12 screws!) and unplug the speaker.
loosen the setscrew and remove the VFO knob.
pull the vol and SQ knobs off.
remove the 4 screws holding the front plastic in place, and remove it. Keep track of the buttons inside.
remove 3 small screws holding the front panel board in place and unplug it.
The lamps are in little green covers on either side of the LCD. unsolder and remove them, then remove the covers. Put the covers on the new bulbs, and clip the leads. Solder the new lamps in place.
You are now ready to assemble the unit unless you want to replace the backup battery. It is a CR2032.
Replace the front panel board, and its screws.
remove the 4 screws that hold the front panel frame in place, and the front panel frame will open outward. The backup battery has straps and they are soldered to 2 posts. Note the polarity, and remove the felt covers, then unsolder the straps from the posts.
You will need to solder these straps to your new battery. Try to use high heat to solder quickly to avoid lots of heat inside the battery, but some is unavoidable. I am sure this will shorten teh life some, but it is better than no BU battery...
Once the straps are soldered to the new battery, put the felt under the battery, and solder the straps back to the posts. replace the top felt. and the battey replacement is complete.
I understand that the VFO knob can come loose. Check the nut on the VFO shaft and tighten is needed.
The unit can now be reassembled. Take care to keep the front panel buttons in place as you install the plastic front.
check for fingerprints on the LCD and the inside of the clear window in the plastic front panel. A small clean lint free cloth will help here to remvove any prints or dust.
also remember to plug the speaker back in.
enjoy your new TW-4100.....