No idea, but you could measure the voltage on the socket. Should it blink when ringing? Then probably 48V and could be 50mA. CB phone sets use 48V AC ringing voltage.
1990 is vintage? I feel old. Anyway, it could be a neon bulb. Phone companies designed stuff to last, and neon lamps don't have filaments to break.
Looks like this would fit.
https://www.amazon.com/Jameco-Value...ndustrial&sprefix=ne-2h,industrial,101&sr=1-1
Don't think a neon bulb would fit, the plastic bezel is essentially flush with the top of the socket. After Googling it more, I think it is most likely a T-1 3/4" 48V instrument bulb, which are available NOS, but at more than the phone cost me. Not sure there is enough room to rig up an LED resistor diode combination either.
Looks like a standard bi-pin bulb, they were ubiquitous in telecomm equipment until replaced by LEDs. Some types had 10K - 100K hour service lifetimes.
https://www.jkllamps.com/incandescent/bi-pinlamps
https://www.jkllamps.com/incandescent/bi-pinlamps
Cut the PCB tracks, use a diode and resistor to jump tracks, feed a chosen LED, many choices are available for color and size.
Fit the LED where the bulb was fitted.
See polarity with a meter, space permitting I use a marker to write polarity on the board.so that it is easier for me when doing repairs.
Fit the LED where the bulb was fitted.
See polarity with a meter, space permitting I use a marker to write polarity on the board.so that it is easier for me when doing repairs.
