It's an age-related problem involving a dirty/worn ring resistor that's swiped with aperture changes. I have a pretty black EL that developed the problem. You might contact Essex(http://www.essexcamera.com/)
but I suspect you'd be happier with an FE or F3--both can handle NAI lenses, thanks to a flip-up AI tab. A clean FE would probably cost less than the repair bill on your ailing EL.