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Discussion Starter #1
I have the P120 single slot radio in my 2000 OBW. It has 155k miles on it and is new to me as of about 152k miles.

All of the lights in the radio are not coming on. The radio functions perfectly fine otherwise, it is just a bit of a nuisance to not be able to see it at night. The illumination in the dash works as well as on the climate controls, but the radio does not light up when I turn on the headlights.

I thought it might be a fuse, but it seems that the illumination is all under one fuse, so if the fuse was blown none of the dash would light up it seems to me.

I already have my center console torn up and the radio out. I attempted to hook up a voltage across pins 1 and 7 to simulate the voltage the illumination would receive during operation, but that didn't seem to work. Meaning that the lights are all dead, a fuse in the radio itself (if there is one) is blown, or because I don't know entirely how the radio works did not have enough power on enough pins.

As a computer engineering student I am not afraid to tear into stuff to diagnose and am also poor so would love to hear low cost options if they exist. :) I have some free time so I am seeing what I can do about some of the car's quirks for not a ton of money.

Anyone have any ideas? I am new to subarus so I do not know a ton about their inner workings yet.
 

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I'm not familiar with that radio, but pins #1 and 7 are for the radio control lighting (when the headlights are turned on). I doubt there's a fuse inside the radio in the lighting circuit -- more likely the bulb (or bulbs, if more than one) is burned out.

There's not much information around about the radio circuitry; but if you're okay with getting inside, it should be possible to find the bulb(s), and hopefully replace if blown.
 

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Discussion Starter #3
I have opened the radio and the panel lights are all on a little faceplate the comes off rather easily. It could very well be that they are burned out, but none of the lights turn on which is what made me suspect something else like a fuse or bad wire.

I had read somewhere that a wire touching the wrong thing somewhere could cause this sort of behavior, that true?
 

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Having done a similar job years ago (and yours may be different) I found that one tiny bulb fitted into a recess and lit up a clear plastic bar that travelled to and encircled several knobs to light them up. The bulb was burned out and easily replaced with a tiny 12 volt bulb with 2 long pigtails, which was sourced at Radio Shack.

As well, on another radio the culprit was a ribbon cable that fed the display. Simply pulling up on the connector lock on the ribbon cable , removing the cable, cleaning its end with a pink eraser, reinserting it, pushing down the lock, fixed that problem. Good Luck!
 

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Discussion Starter #5
It looks like there are many small green cover bulbs (LED sized, but don't know that they are LED).

I just verified with a voltmeter that the two pins are indeed sending the voltage difference to the radio unit, so it is something in the radio unit...

Guess I just need to swap one of the little bulbs out and see what happens then.

Should I take pictures and make up a guide should this work for me? Is that something that others might be interested in?
 

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Sure, give changing a bulb a try, and if it works (let us know), post a "how to", with pics, thread in the DIY sub-forum.
 

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Shortly after inheriting my 2000 OBW the light in the radio area that showed what station was tuned in, what device was chosen (FM, AM, Tape, CD, Weather band), volume and other levels (Bass, fade, etc.) started to go out. I would "flick" it with my finger and the light would come back on. Now that trick does not work. All of the other lights in the HU still work though. I also predominantly listen to an aftermarket XM radio unit running through a cassette adapter which has it's own light (and lots of cool backgrounds to choose from), so I haven't worried about it much.

This leads me to believe that 1. Different components of the HU are individually lighted, like you've observed, and 2. At least in my case, there is a connection problem, hence the tapping or flicking solution that worked for a while.

I am interested to hear about what you come up with. I'm not afraid to delve into the dash and HU but it'll be cool to see what you find before I make the journey.
 

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Discussion Starter #8
Haven't figured out a ton yet...

(Image embedding didn't seem to work for me... so links instead)

So, I have looked at the radio some more and have taken a volt meter to the individual bulbs to see if they are out or not.

Here is a picture of the front of the panel that has the lights. The light locations are circled in Yellow. Where I have the two question marks I suspect that there are two more, but that they are internal to the display piece. Not having a soldering iron at home, I wasn't able to expose that and verify for sure.
Front | Flickr - Photo Sharing!

Here is the backside of the panel. I circled in red the solder points of of the bulbs. The ones with question marks I am not sure of as I can not see them on the other side, but they are underneath where I placed the question marks on the front side. I suspect that they are bulbs as well because they are identical solder points and also because they are connected to other bulbs on the board.
Back | Flickr - Photo Sharing!

The thing that gets me though is that the two pins on the left that are being pointed to by the yellow arrows connect to ALL the bulbs on the board that are confirmed, but only the top half of the two with question marks. The other interesting thing is that the pin on the left with the number 2 on it connects to the bottom point on the two with the question marks, but to nothing else. The spring looking thing on the right connects in with the non question marked ones and the top half of the question marked ones. I figure that is the ground as it makes contact with the metal of the radio housing when it is attached to the radio face.

Even more interesting to me since they are not turning on during operation is that from either of the pins with the arrow I can continuity check from the pin to any other solder point that is outlined except the bottom of the two question marked ones. There is continuity between any of those points from any other point and to the ground spring. Then there is continuity from the number 2 labeled pin on the left to the bottom half of the question marked ones.

There is not however continuity across the two question marked ones.

But would those not having continuity kill the whole thing?

So there is power coming in the illumination pins of the radio harness. As far as I can tell there is continuity from input pin to ground on this panel, except for across the two with the yellow "2" on the panel. These connect into the pin labeled with the number 2 though.

Without an actual schematic I am kind of at a loss... Any thoughts?
 

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My craft is repairing electronics. The "bulbs" in your photos are LEDs, so they are not likely burned out. My guess is the culprit is oxidation on the connectors to that board. If you are willing to gamble $18, go to Radio Shack and buy their DeoxIT twin pack. Wash all of the connections with DeoxIT cleaner, including the ground "spring" and the surface it mates to. Follow up by spritzing them all with Gold protectant. Oxidation on small electrical connectors is invisible to the naked eye but causes plenty of gremlins.
 

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Going back a bit, when you said "All of the lights in the radio are not coming on.", did you include both the controls (knobs, buttons) and the radio display, or just the controls? (The "display" is that gray part that has the two question-marked lights on either end and show the station frequency etc.)

The reason I ask is because I believe the radio control lights might not use the radio ground. As noted earlier, the power for illumination is provided through pins 1 and 7 of the radio connector. One of these pins goes to the common illumination fuse (as noted in post #1). The other goes to the illumination control -- the device that allows you to vary the intensity of the dashboard lighting -- and it is this control that provides the return path to battery ground. (This is the same for all the dashboard controls such as the heater, the Hazard switch, the seat heater switch bulbs, the main power window control switch, the AT selector lever position light, etc.)

I'm not familiar with the stock 2000 radio, but suspect that the connections for the bulbs on that printed circuit board (the one in the photos) is set up so that the illumination of the knobs and buttons on the radio can be varied with the illumination control (the four circled connections), but that the radio display illumination (the question-marked connections) is not variable -- it would stay at one "brilliance" regardless of the setting of the illumination control. Thus the question whether all radio lighting is out, including the display, or only the controls.

Radar could be right about the visible "bulbs" being LEDs, but I can't really tell for sure from the photo; they could be "micro" or "mini" incandescent bulbs which are not larger than typical LEDs. I've replaced ones that are similarly mounted on a plastic base. (If they are LEDs then I agree, they are not likely to all have failed.)

Is your multimeter a digital type? When you put the test probes across the two solder points on any one of the four circled connections, is there continuity, and if so what is the resistance reading? If you reverse the test probes, is the reading the same, or does it change, and if the latter, to what?

If the resistance reading is low and doesn't change, then I suspect the lights are incandescents. If the reading changes, then they could well be LEDs. This can be verified with the meter's "diode" test function, if it has this. (Meters with a diode test function will have a high reading with the test probes connected one way, and a lower reading with them connected the other way. The diode test reading on some digital multi-meters is actually Voltage, and the lower reading will be the forward Voltage across the diodes, which is typically in the 0.6 Volt range.)

If the reading across the solder points is very high in all cases, then it's possible they are just burned out incandescent bulbs.

Also, I believe the radio controls are lit up with the rest of the dashboard illumination, whether or not the radio is turn on. If so, then it should be possible to make sure that pins on the main radio board that correspond to the two "arrowed" pins on the pictured board are connected back to pins 1 and 7 of the main radio connector. This would eliminate that question of there being a fuse, or even a bad connection.
 

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Discussion Starter #11
Radar - I suspected LEDs at first, but then seeing the piece of plastic they lit up from the side of the bulb/LED I was suspecting they were not. I just took some pliars to the covers to see what was underneath as well to be sure. Here is a picture.
Normal | Flickr - Photo Sharing!

Going back a bit, when you said "All of the lights in the radio are not coming on.", did you include both the controls (knobs, buttons) and the radio display, or just the controls? (The "display" is that gray part that has the two question-marked lights on either end and show the station frequency etc.)
When I have the radio in the car and the lights on, the entire radio panel is dark. The controls, the display, all of it is dark and there is no illumination on the radio at all. Hence the difficulty in seeing it at night. :)

The reason I ask is because I believe the radio control lights might not use the radio ground. As noted earlier, the power for illumination is provided through pins 1 and 7 of the radio connector.
I could see that being the case. The only reason I thought they were grounding to the radio case was because the two solder points on the right side of the back are connected to a pad that connects to the ground spring. Not having a schematic it is hard to say for certain what is going on, but I see the connection there

What you said about the display going to one place and the rest going to another so they can dim makes sense to me and why there would be the number of different pins that there are. That being the case, I don't understand why they would be connected to the spring ground as well?

Radar could be right about the visible "bulbs" being LEDs, but I can't really tell for sure from the photo; they could be "micro" or "mini" incandescent bulbs which are not larger than typical LEDs.
See previous link for photo :)

Is your multimeter a digital type? When you put the test probes across the two solder points on any one of the four circled connections, is there continuity, and if so what is the resistance reading? If you reverse the test probes, is the reading the same, or does it change, and if the latter, to what?
The meter I had access to at the time was a very simple fluke one that is probably more useful in house wiring. It was all I had access to at the time at my university and it doesn't even have precision beyond whole numbers... Nothing past the decimal point on that one so all I could really do is check for continuity. I am a computer engineering student and this next week I could get access to much more accurate equipment in our lab.

If the reading across the solder points is very high in all cases, then it's possible they are just burned out incandescent bulbs.
It seems there are some that are burned out. Three of the visible ones look like this one here while the other two visible ones look like the first one I linked to. I won't be able to check the display ones until I can get to a soldering iron though.
Burned | Flickr - Photo Sharing!

But would having some of them be out kill the whole thing? I also thought that when incandescent bulbs burned out there was not continuity across them. When I checked that before, I had continuity across all of them except the two on either side of the grey display.
 

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But would having some of them be out kill the whole thing?
Ah, we're getting to the interesting part, and where I would be doing some circuit tracing.

Yes, if a bulb is burned out, then it should show no continuity (or a very! high resistance) across it's terminals. However, what if several bulbs are each connected across the same two supply lines (the term is "in parallel")? If one burns out, if it's still connected in the circuit, the meter would measure the resistance of the other bulbs across the same points, so it would show continuity. Wiring the bulbs in parallel is the most common approach, so if a bulb isn't visibly broken or burned, it has to be disconnected from the circuit to test for continuity. (A darkened bulb usually indicates it's burned out, but a clear one could be too. A set of magnifier glasses can sometimes be used to examine the filament more closely through the clear glass to see if it's broken.)

In some cases, the bulbs might be wired in series, that is, one after the other so that the current through one goes through the other. In this case, for example, two 6 V bulbs in series can be wired across a 12 V source. Each would light up with normal brilliance. However, if one burns out, neither will light up.

Finding out how the circuit board is "wired" can help determine if the bulbs are in parallel or series and this could answer whether one or more burned bulbs can cause all, or at least more than one, to be off as well.

What I suspect the wiring might be is the four circled bulbs are connected in parallel across the two pins (1 and 2) of the connector at the lower left. Pin 2 goes to the 12 V supply; pin 1 goes to the illumination control, and through it to ground. The two bulbs circled with question marks are also connected in parallel, with one side going to pin 2, but in each case, the other side goes to the ground of the board, which is also that spring that contacts the case ground of the radio.

If this is correct, and with the board out as in the photos, there's continuity between the connector pins marked 1 and 2, at least one of the four circled bulbs is good. Similarly, if there's continuity between connector pin 2 and the ground spring, then at least one of the two bulbs with question marks, which are for the display, is good.

With at least some bulbs appearing to be good, the likely cause of none coming on is there isn't 12 V coming to the connector. As noted earlier, one of the two pins should go directly back through the radio to main connector pin 1 or pin 7 (the 12 V supply).

Just a process of elimination -- bulbs, circuit on the sub-board, connection to the power source.

The possibility of there being bad connections, either at the connector on the board, the spring ground, or somewhere in the rest of the radio, remains, especially if at least some of the bulbs are good.

But it wouldn't be the first time all the bulbs would be found to be burned out. It's not noticed, or worried about as long as some, or one, bulb is working and things can be seen, but when the last bulb goes, the darkness then becomes both noticeable and a problem. (Or, as I believe is your case, the car changes hands and the new owner notices there's no lighting.)

You're on the right track . . .
 

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Discussion Starter #13
I didn't even think about them being wired in parallel and thus giving me continuity...

I have traced the path once on the board. I'll do it again and draw it onto the picture when I get a minute. Some of them disappear to where I can't see them though.
 

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Discussion Starter #14
Ok, as best as I could trace them this is what I came up with. Sorry about my crappy drawing.

Wiring | Flickr - Photo Sharing!

Some of it doesn't make a ton of sense why they would do it that way... Like off of P1 there is the blue path that winds around and then eventually to the bulb just to the right of the brown connector on the left. But the right off of the P1 there is that orange path that connects into the other part of the same bulb. So... unless there is crazy voltage dropping happening along the blue on it would be the same voltage?

I realize that this is hard to analyze through pictures with crappy drawing as well.
 

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It can be hard to trace where the printed circuits go; all the more so when it's a two-sided board, which is what it appears to be in this case. (When a trace ends in a pass-through, identifying the pass-through on the other side can be problematic, and sometimes they end up under a component and cannot be seen.) I suspect this could be the reason for the appearance of strange connections and traces that seem to go nowhere.

A multi-meter (continuity check) can come in handy here; then again, when there's parallel paths such as the bulbs, it would also require unsoldering one side of each bulb so that the paths through the bulbs don't add to the confusion.
 

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Discussion Starter #16
I put numbers down for the pass throughs I was certain on, anything with a question mark disappears behind the display unit. I will probably be able to do some soldering later and could probably find out better where those go, but until then this is the best I can do.
 

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Knowing the circuit can be helpful, but isn't necessary at this point.

We know that pins 1 and 7 at the main radio connector are the dashboard lighting inputs. So there should be continuity between pin 1 and one or more pins on those two connectors going to the sub-board (photos). Similarly, there should be continuity from pin 7 to one or more pins on the two connectors going to the sub-board. (In regard to the latter connectors, I'm not referring to the connectors on the sub-board itself, but the mating connectors on the radio.) Probably useful to make sure there is continuity, and which pins of the sub board connector(s) are related to pins 1 and 7.
 

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Discussion Starter #18
Well, just to see what happens I went and purchased a new 12 volt mini bulb. I will be able to get it soldered on tomorrow and test it to see if there is light or not.
 

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Discussion Starter #19
So they came in a pack of two. I replaced one in the display unit and one elsewhere on the board. I put it back in my radio and lo and behold it works.... mostly...

The one I replaced in the display unit lit up, but the one I replace elsewhere did not. There are 7 total on the board so I am going to get enough to replace them all and see what happens. 6 dollars at radio shack total ain't too bad...

Radio Shack carries a 12 volt mini incandescent bulb that is slightly taller than the stock one, but fits none the less. Once I have replaced them all I will report again if it was a complete success or not.

I wasn't inclined to believe they ALL burned out on account that it was the entire face panel that was dark... But I guess after 165k miles on the OEM radio it is certainly a likely scenario :)

Also, the little green things that cover the bulbs. I lost one and another ripped. any ideas for how to color them? It might be nice to do something other than green as well.
 
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