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About a month ago I got sick of burned out lights in my radio and spent a week with the radio in various states of disassembly experimenting with solutions. I wrote down detailed instructions of what steps I took to replace the bulbs and what bulbs I used. It ended up being a lot longer than I expected but I thought I would post it for others to decide if they want to try it or if this would convince them to leave it alone.
Essentially, I found that a 5 volt lamp was probably used in the radio when the maximum voltage was 6.8V which would explain why they don't last. I also found that I kept my lights at an easy to read brightness of about 80% intensity which happens to deliver 5V to the radio lights so theoretically they shouldn't burn out soon but I've only got a month of daily usage so far. I'm only posting it because the light intensity and color exactly matches the others on the console so I think I got it right.
Hope this helps.
Mike H. II '93 850GLT '97 V70
1. Remove radio from car. In my case, the radio is an SC-810 from a ’93 850 with seven bulbs. Later year radios have sockets that are removable with a quarter turn and a different number of bulbs but the end result is the same. Although it is physically possible to remove the printed circuit board (PCB) that you will replace the bulbs on with the radio connected, unless you do not have the code, trust me that you should remove the radio and go to a well lit area that you can sit and work at. My kitchen table with a couple paper towels was perfect. Push the two release tabs on either side of the faceplate, pull them and the radio out to reach the thumb latches on the connectors to disconnect them and simply pull the antenna cable out of the radio and its free from the car.
2. Disassemble the radio. The radio is a nice cube shape now that you can place on its back with the faceplate facing the ceiling for disassembly. Stop and get a ziplock sandwich bag for the little knobs and screws. All the knobs pull straight off but if they are like mine, they haven’t been disturbed in a long time and they are stuck more than finger tight. Get a small thin screwdriver to pry them off and get a small piece of heavy paper to place under the screwdriver when you pry. Remove one Phillips head screw on each side of the radio in the black plastic track closest to the faceplate. On the top and bottom of the radio you will now need to gently pry the faceplate off the metal frame of the radio. If you go slow and gentle you will be able to see the spots that you need to pry. Now that the faceplate is off, zip up the sandwich bag with the small pieces and place the faceplate and bag somewhere out of the way and safe. When you see the complexity of the faceplate you will understand why dropping it or sitting on it would be a disaster. If you want to replace the bulbs without removing the holder from the PCB (more tedious but potentially less likely to damage something), you can skip to the next step now. The PCB with display pulls straight out but you need to release the 4 bent metal tabs holding it down. A pair of needlenose pliers can be used to twist the tabs so they can pass through the slot in the PCB. Don’t bend these anymore than you have to – the metal is soft and if it breaks off there is no practical way of replacing it. Now the stressful part – the board pulls out but there is no good way of pulling or prying. Be sure the bent tabs are passing through the PCB and try wiggling around a little to see if you can get it to start to pull out. The header pins can stand some wiggling but don’t get too rough with it. To help you visualize what is behind the board – look for little white plastic latches coming through the board from the other side around the area above the preset buttons and near the volume knob. These latches are at both ends of a row of pins on the back of the board – these are the only things holding the board in. Once the board is free, place the radio somewhere safe and turn on the soldering iron.
3. Replace bulbs. Some sort of magnification to work under will be very helpful for the soldering steps. The bulbs are soldered into a socket which is soldered to the PCB. If you are handy with solder braid to remove parts from a board then I recommend removing the socket from the board for this work. Otherwise, you could have left the PCB in place in the radio and spent a lot more time fishing the bulb leads through the socket. Either way, I removed the bulb from the socket by twisting it back and forth until I fatigued the leads and they broke off where they exit the glass bulb. Now the two leads are visible at the bottom of the socket and they can be pulled out of the socket from the outside and left to stick out to the side. Don’t desolder them or cut them yet. The bulb has a small rubbery blue cover over it that must be reused. It can tear easily so take your time with it and gently pull the edge back all around to unstuck it and slowly try to slide it off. There will be a little bit of a vacuum holding it on but it will slide off if you take it slow. Transfer the blue cover to the new bulb, it will slide right on. Place the new bulb all the way down in the socket by fishing the leads through the socket and out the side if still attached to the board or just stick it through and bend the leads up if removed from the board. Make sure the leads don’t cross or otherwise touch each other in the socket or anywhere else. Now, wrap the lamp lead around the old lamp lead one time right next to the socket. Solder the leads together on each side and trim the excess leads off. Be careful you do not move the bulb around in the socket too much or you will break the lead off just like the way the old bulb was removed. Resolder the sockets to the board if you removed them.
4. Reassemble radio. If you removed the PCB, it will simply press back into the sockets but be sure your bent metal tabs are straight and watch for them to line up with the slots in the PCB. It should not take much pressure at all to make the pins enter the headers. Twist the metal tabs just a little bit to lock the board in place again. Wipe the display and inside of faceplate window to remove fingerprints. The faceplate snaps back on once all the bulbs line up with dimples in the plastic faceplate. Replace the two screws on the side and press the knobs back on. Plug the radio in and try it out.
5. Bulb info. The Radio Shack 272-1092 bulbs are correct in every way except they are 12V and will be noticeably dimmer than stock. The maximum voltage the bulbs will see in use is about 6.8V. From experimentation I found that setting your dash light intensity at about 80% runs the radio lights at about 5V. Also, its hard to know for sure but the original bulbs seem to be 5V so that could explain why they don’t go the distance. I found the new 5V bulbs to be slightly brighter than the remaining bulbs which might be due to their age so I replaced them all. But, when the job was complete the intensity and color of the new bulbs exactly matched those of the other dash lights so I felt good about my choice. Leave your dash light brightness at about 80% and you’ll probably never have to replace bulbs again. I went with a 5V 60mA T-1 size incandescent micro-lamp with wire leads which is not too unusual but not common enough to be at Radio Shack. BTW, micro-lamps seem to be available in 5V, 10V, or 12V but if you can find at 7V its worth a try. I found my 5V’s in a 10 pack at Newark Electronics for $14, (newark.com part number 96F5813) they have a $25 min unfortunately so I had to add a couple small things to the order.
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