Philips Wake-up light HF3510 Touch screen not working

[Sören_Marodören]

Hi,

A friend came to me with a 8-9 year old Philip HF3510 Wake-up light that didn't work properly.
The problem was that the four Touch screen buttons on the front of the lamp (-, Menu, Select and +) didn't work properly.
The light react when touching them by generating a klick sound, but nothing more happens. (You set time, alarm etc via these buttons.)

After disassembling the lamp a few of the larger electrolytic capacitors was found with bulging cans. (2200 µF/6.3V, 470 µF/10V)
These capacitors had very low capacitance when measuring them. No leakage on the board.
I replaced them with new capacitors and tested if it solved the problem.
Unfortunately it didn't fully solve it, but it become a bit better. Now, I could start the light (with the fault still there) turn it off and start it again in a few seconds, and the light worked.
My interpretation on this is that there is a start-up issue probably related to the voltage generation

I then decided to replace all Electrolytic capacitors.
When replacing them I measured the capacitance on the old, but could not see any with too low capacitance.
(I can't measure ESR. Maybe a too high ESR can cause this problem...)
After re-caping I tested the light and now it worked.

Maybe this is a common problem on these lamps.


I must say that I'm impressed by the design of this lamp. There are so many special design parts that I haven't seen anywhere else.
And so many parts that are put together by screws. It must have cost a lot in money and time designing it.
Hats off, Philips. (But you could have used better quality caps... )