E39 Business Radio Backlight Issue Solved
I'm a noob to BMW, so I've been soaking up great info in this forum to improve my '00 528i. Here's my chance to give back- I'm good w/radios and electronics (ham opr) and managed to fix my factory radio lamps; will share a few pointers about it here.
This is not about the lost/missing pixel issue- it's just about dim/dark areas in the display- I've seen many posts on both things. Fixing mine has made the center display of the vehicle look SO much nicer- big difference. Anyway, the orange LCD needs a backlight to work- radio provides this via 14 small incandescent lamps that stick thru a plastic shroud behind the display. In my case anyway, none of the lamps were burned out, they had just fallen off of the circuit board! They are attached by a "surface mount" technique with glue and solder, which failed over time from vibration and temp cycles.
Here's how to fix: pull off volume knob and stick a 2.5mm allen wrench into that little torx screw in the slot below- turn gently 90 deg CCW and tug the left side of the radio out from the dash. Disconnect the single connector- you have to swing the u-shaped latch forward toward the front panel to lever the connector out. No worries about a code reset here- this radio only will work within a BMW computer environment anyway. Take the radio to a well-lit padded bench and heat up your small pencil-tip soldering iron. Pry off the top and bottom covers of the unit- no fasteners. There is a triangle-shaped brace on the back of the display shroud on top side- release this by squeezing the tip of the latch where it goes thru the circuit board from the bottom, using needle nose pliers. Now remove the long thin lighting circuit board from the back of the display shroud- it's held by 3 torx screws which you can reach with an allen wrench thru 3 holes in the back panel of the radio. Slide/twist the black connector off the end of the board, and remove the circuit board from the radio. You will now probably see that several of the 14 white lamp holders are missing (mine lost 4). Pick up the radio and hold it face up, and shake the missing lamps out of the shroud area- don't lose 'em!
Remainder of repair involves prepping the solder pads, soldering the lamps back onto the board, applying a little CA to hold 'em good, testing the light strip with a 5V source (optional), and reassembling. It's not hard technically, but proper tools and technique help a lot. I'd be willing to do this repair for other Bimmerwerkz folks for a small fee if you want to ship your circuit board (or whole radio) to me and cover shipping....just a thought. If the lamps really are burned out, they are a standard "grain of wheat" size available on the Bay- I have a bunch of them.
Now to get on with that thermostat replacement......fun!