Radio display dim or no backlight

Hi everybody,
I bought my '96 318is 85k about a year ago. It's a great car, love to drive it. It came with a standard Alpine radio system fitted into these
cars after '96. The backlight in the radio has never been working eversince I bought the car. But occasionally it would go into a dim mode. Once, a few month ago, I was driving on a highway and for no reason it illuminated all the way up, which means that bulbs/leds are working fine and aren't burned out. But it's never worked since. There must be some electrical issue.
I was browsing through this NG and found many people having the same problem but never found any do-it-yourself solution. Does any of you have any experience and advice in fixing that? Not necessarily take it to the shop.
Any help would be appreciated!! Thanks, Piotr
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