Thursday, 17 February 2011

No user servicable parts inside - Philips HF3490 Wakeup light repair

I'm not a morning person. I don't like getting up early unless I've got a very good reason to do so. When I was working on a project in Lowestoft we would get up at 7AM, and I could mange this - despite the very late nights coding or working on electronics design for the project. What it turned out to be (aside from the motivating job to get up for), was the bright sunrise we would get in the morning on the coast.

I came across the Philips Wakeup light which can wake you up with a gentle 30 minute sunrise at your chosen alarm time - followed by more usual (yet gentle) alarm noises, FM radio or music from your iPod. I wanted one, but sadly the iPod version was subject to a recall and was not available for purchase last year. My parents got me one as an IOU last Christmas, and when the product was re-introduced onto the market, they duly sent it to me.

I love the stylish design of the Philips Wakeup light, and for a small lamp-sized object, it is a very good speaker system for your iPod. Not Hi-Fi quality (and it is only mono), but it is certainly good - featuring a cleverly designed ported speaker inside.

Sadly - my wakeup light got a bit cranky lately - a couple of times it has refused to light, and would require disconnecting the mains and power-cycling for the lamp ballast inside the unit to reset and have another go. Last weekend it finally bit the dust (less than a year old), with a fault which appeared to be a stuck volume button - the unit would dial its-self to minimum volume and not respond to any other controls. (Not so good as an alarm any more!)

Having quizzed my parents about the possibility of finding a receipt for it (I still have all the original packaging), it seemed that we would not be able to find the proof of purchase necessary to send the item back to the (online) retailer it was purchased from. We couldn't even identify which retailer it would likely have been. (There is a moral here.. to put receipts or printed copies of order confirmation inside the products box if you're going to take the trouble of keeping it!)

Anyway, long story sort - I figured I had nothing to loose by attempting a repair. I figured that Philips would not entertain a warranty claim without proof of purchase. (I later realized that the recall and serial number should prove fairly conclusively that the unit WAS under warranty!).

Out came my trusty bag of Hozan brand JIS screwdrivers. I cannot recommend these enough for repairing electrical goods which have fasteners made in Japan or China. Real JIS screws have a single dot punched on them on their face - the ones in the Wakeup light didn't. I'm not sure if Chinese cross head screws are actually JIS, but these screwdrivers fit so much better on most electronic equipment that I tend to use them exclusively (for non-live work).

For live-work, or general cabinet / electrical work where one "might" encounter live wires, my other tool of choice is the Wera Kraftform series of VDE rated screwdrivers. If you get the right one for the screw, they are amazing. (They do wear and break if you misuse them with the wrong screws).


I'm an electrical engineer, and routinely work with mains voltage equipment. If you do not, you might be better talking to Philips customer relations than trying this.

Getting killed can hurt, and tends to be inconvenient.

So.. boring bits out of the way.. lets get to the good stuff!

I separated the lamp from the iPod dock, then peeled off the four rubber feet hiding screws for the lamp diffuser. The fifth rubber foot doesn't have a screw under it.

There are another four screws hiding under the top plate of the lamp (the one labeled) "PHILIPS". Unfortunately, it appears this has been designed to be assemble only - and I broke two of the four plastic snap-ins holding it in place. If you have to remove this, I'd suggest trying to apply pressure diagonally across the top of the lamp diffuser whilst an assistant levers up the lid. I just levered the lid up, and it broke. (Oh well).

I find it really frustrating Philips didn't make this more accessible or less easily broken, but during the course of my investigation, I decided the unit had clearly been designed not to be serviced. Perhaps Philips do take them apart to repair, and have a stack of spare plastics to hand - but my guess is that for a £150 product, the built cost is about £40-50, and they will just replace, rather than repair warranty returns.

Separating the sides of the lamp diffuser is difficult, and I started at the bottom, using my thumb to lever between the diffuser and moldings on the base of the lamp. This freed a few snaps along the side of the housing, and allowed me to get a guitar plectrum into the seam between the diffuser and white trim along the side of the unit. Both sides of this white trim can be released, but you only really need to release both sides on the side with the controls.

Once the diffusers are eventually removed, you can free the button trim by levering at the snaps joining it with the button unit with a small flat screwdriver. The result is here:

The opposite side trim is even more delicate, but you should not need to remove it from one of the faces of the diffuser. Removing the top vent ring is somewhat awkward, and requires distorting the side-trims carefully to unhook them from it. The diffusers are glued into the vent ring, but this comes away with gently pressure. Be careful not to distort the diffuser too much when removing it, as the screw-tabs retaining it are slotted through holes in the side of the vent ring.

I'm cheating here - this is a picture of the lamp during re-assembly after the repair but I thought it would show the idea..

Having removed the diffusers and side trim, four long screws are all that remains to access to the innards of the lamp. It goes without saying.. but you did unplug it already - right? Inside the lamp is a mains fed HF fluorescent lamp ballast, which operates at very high voltages - upwards of 300V DC.

It is very wise to leave the unit "a while" since you last had it plugged in before opening it up. The exact definition of "a while" might be minutes, hours or days depending on the appliance. I've seen TVs retain very high charge in capacitors for days after being unplugged. I have not measured the discharge time for this circuit, so can only advise caution. I waited about five minutes and was careful not to poke at the ballast PCB too much until further time had passed.

The lamp was pretty well dead - after less than a year. One of the heater coils had open-circuited in the lamp. I don't know if this was due to my "encouragement" trying to "unstick" the volume button with "vibration" (read - banging the damned thing in frustration against the desk) - but from the looks of the tube and previous no-light symptoms, I'm fairly sure it was on its way out before then.

Removing the bulb was a bit of a pain, as Philips have gone to a lot of trouble to try and ensure the things don't get dislodged in transit. Fortunately, the glue they used to goop it into place is soft and can be cut through with a small screwdriver quite easily. There are four small cross-head screws holding two clamp shells around the lamp which also need to be removed.

Clipped in the center of the tube is a white-painted electrode which acts as a "teaser" to help the ballast achieve flicker free dimming of the lamp. This will be LIVE when in use, and is (I suspect) the main reason why Philips had to make the lamp in this unit non-user serviceable. Providing access to enclosures containing unexpected live-electrodes is not a generally good thing - and you could bet someone would try changing the lamp live and get zapped.

Remove the clamps, unclip the insulator on top of the lamp (noting its orientation), then pull out the teaser electrode. It should now (just) be possible to lift the lamp up a bit. Unfortunately (to save cost one presumes), the lamp socket is basically a one-way grip affair, and requires gently levering the contact electrodes back from the lamp electrodes. This is the assembly after removing the lamp:

I love the way Philips have engineered beam springs into the supports for the lamp in order to make it more resistant to failure in transit. This is a really clever touch to what I view as a superbly engineered product. I noticed that the electrical build quality isn't that high in some places but then this is a "Made in China" product, and made for a good price. I was a bit concerned to see dark brown "goop" used to retain components like capacitors on the ballast board this compound is similar (in appearance at least) to the kind of thing one might look out for as a potential cause of current leakage when repairing TVs or PSUs - some kinds of adhesive looking like this lower in resistance when they get old.

Anyway - I replaced the lamp with an equivalent Osram model. I'd have liked to have found a Philips bulb (MASTER PL-C 827 26W 4pin), but I couldn't find one cheaply. It turns out that the thickness of the bulb base and glass envelope construction is not standard, so I had trouble fitting the Osram lamp. I had to file down two recesses on the side of the lamp base to accommodate the retaining clips, and was not able to screw the retaining clamps down completely. Still - it works, and it is held in. More irritating is that the insulator cap for the teaser electrode doesn't fit with the Osram lamp - so I had to leave it out. I strongly recommend you use a genuine Philips lamp if you want to repair your own out of warranty wakeup light.

Fixing the buttons on my unit (so far) has seemed just to require re-seating a badly assembled ribbon connector made at the factory. It is the one on the left in this picture.

This said - I'm not 100% convinced the fault has gone away, as I did find the unit on zero volume again the other day. On closer inspection - there has been factory rework of the main alarm PCB assembly, right in the area concerning button input decoding. The factory have done a very poor job of this rework, leaving an uncleaned residue of potentially corrosive / conductive burnt flux on the board where they did the rework. I would have expected (or hoped for) better from Philips:

I cleaned the worst of this residue, and if I have any further problems with the buttons, I'll probably de-solder and rework some of the components in this area. The macro photographs have made me suspicious of the solder connections on L309-310, along with others in the area.

Anyway.. it works again:

(Don't try this at home - put the covers on first, and remember that live teaser electrode on the lamp too!)

Good luck!


  1. Very interesting! My boyfriend and I have an older version of this light. The knob to control the brightness of the lamp stopped working a while ago. Tonight, curiosity got the best of us and we started to disassemble it. Luckily, Google pointed me toward your page where your images and account of your experience satisfied our curiosity. Thanks a bunch :)

  2. I hope you get either got it sorted, or had fun trying.. Sometimes just images to help along the way are useful, and that is really why I posted this entry.

  3. Thanks for the article, helped me quite a lot with taking apart the lamp. Too bad I couldn't repair the buttons.. Any idea how to open that compartment?

  4. Guus: Did your buttons fail in the same way?

    I obviously didn't find the original fault with the buttons, as mine has stopped working again. I will hopefully get round to looking at it again, so will follow up here if I discover what the underlying problem is.

    The long plastic trim which forms the outer case of the button assembly can be removed with a small flat screwdriver used to gently lever at the plastic snap-ins which hold it in place.

    The circuit board entry was melted in place during assembly, but I was able to slide it back and gently lift it out of its groove without cutting the melted plastic posts which hold it.

    Having partially removed the thin plastic cover, you can get at the screws retaining the button circuit board and side it out of the front.

    I'm not convinced the fault on mine is actually within the button assembly. I think I need to get it on an oscilloscope and check the waveforms. I didn't look in detail at the wiring configuration of the buttons yet.

  5. Hey Peter,

    Mine failed the exact same way (the device operated as if the volume down button were permanently pressed).

    I found that mashing the FM/Volume knob with incredible amount of force (but not concussive force) with your thumb makes it work for at least a while.

    Hope that this helps.

  6. Hi 9b81b9b0-a0ff-11e0-a9e9-000bcdcb2996 (Isn't OpenID wonderful?)

    Your suggestion helped, and fingers crossed, has fixed the problem for now. In my case, it was the "SET" button which needed a lot of force applying to it.

    Since it is working now, I've not dismantled the unit to confirm what the exact fault was but I suspect one of two things:

    1. The actual button units are faulty internally.
    2. The button is shorting out some tracks underneath it, as it has cut into the solder mask.

    It could be that applying the force either helps "fix" the button, or forces it to lift off the PCB and stop shorting out what it is sitting on.

    Since I was never able to reproduce the fault with the circuit boards on the bench, I suspect that the mechanical action of disassembling was performing a similar (and temporary) "fix".

    Best regards,