11 November 2018

Reviving a ceiling lamp from CFL to LED

We've had at home a ceiling lamp for about 10 years, and for the last 4 years it has misbehaved. It contains two 55W CFL tubes with an external HV power supply by OSRAM (Quicktronic Professional QTP-DL 2x55 GII).

The defect was that it would switch off after about 15 minutes of operation and it would restart only after a rather long while. In any case it was not usable at all.

The original configuration.
I tried replacing the gas-filled elements without success, so the culprit must have been the embedded power supply. Since I am still developing my spider superpowers, working upside down on the ceiling is not my thing so I pulled down the lamp on the table. Still about 15 minutes of operation even without the front glass (in case it was a heat issue).

I took apart the power supply case and looked for the obvious, that obviously wasn't that obvious. I simply reconnected everything with the power supply out of its case and it would run for hours. HA! Maybe a cold solder joint failed with heat cycles over time and moving the circuit around sort-of fixed it.

I took my chances and put everything into the metal case, and still working. So I secured the case back to the lamp and ... 5 seconds of operation!

Enough. Either I got another identical power supply or I had to find something else. My readers probably already guessed which one I picked! "Something else", of course.

The lamp base is metallic and hidden against the ceiling so it can be drilled as needed to accomodate a different setup.

Few searches later I learned that there are LED replacements for neon tubes, and they include the power supply too. I chose two circular replacements whose total equivalent power would get close to the original 110W.

Of course I had a look inside the power supply, that is very simple since it has to light up a series of LEDs:

The LED strip power supply.

And the final look, up on the ceiling before placing the cover glass:

Final config. Notice something "light"?
Now the two light sources are independent, so if one fails the lamp will still work at 50% luminosity. If you look closely at the last picture you will see LEDs are "on", dim, but "on". Even with a single wire attached, the culprit is probably some leak of the long driving wire towards ground. I couldn't get rid of it by swapping the two cables, so I consider it as a night light undocumented feature.

We don't use that lamp very often, so hopefully it will last another 10 years!

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