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Philips XWC 121 gear tray

Repaired light sensor board.

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File information
Album name:Rob_TDCi / My Files
Circuit Type:Magnetic ballast with electronic ignitor
Comments:A few weeks ago my XWC121 had stopped working. It comprises a magnetic ballast and the ignitor board below the ballast with the light sensor board in the top right hand corner. When I bypassed the light sensor board it worked. The first thing I noticed was some discolouration around the triac - the triac acts as the switch and carries the full current to the lamp. So replaced this and it works! It would probably last longer with a heat sink, I may look into that some time. For anyone who is interested the circuit uses a capacitive dropper and half wave rectifier to provide low voltage DC power to a 555 timer chip running in Shmitt trigger mode. This produces a nice decisive on/off from the analogue photo transistor signal and introduce hysteresis.
Filesize:253 KiB
Date added:Jan 10, 2017
Dimensions:1200 x 900 pixels
Displayed:27 times
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Comment 1 to 5 of 5
Page: 1

Tom   [Jan 10, 2017 at 11:31 PM]
Interesting and rather elaborate ignitor board there Rob! Mine has what looks like the same or similar light sensor PCB which I think has failed the same way as it has been disconnected. Ballast is the 3 terminal with capacitor setup! I'd certainly feel inclined to bolt a TO220 heat sink on that triac too. I should imagine it takes quite a hammering during startup! Now, you did turn that soldering iron off after you'd finished didn't you? Wink
Paul   [Jan 11, 2017 at 01:45 AM]
Don't want a repeat of the golf incident!
Rob_TDCi   [Jan 11, 2017 at 09:38 AM]
I was always forgetting to turn off the old Antex iron, that's why I ended up buying a neon plug from Woolies.
Rob_TDCi   [Mar 10, 2017 at 07:08 PM]
Well this repair only lasted a couple of weeks Crying or Very sad I've tested all the caps and they are fine but there is a varistor, as used in surge protector leads and that was faulty, so having replaced that, hopefully it will last longer this time. I tried running it for a few hours but in spite of the the discoloration to the PCB, triac didn't actually get that hot.
Tom   [Mar 10, 2017 at 08:37 PM]
Hope you succeed in fixing it Rob! I managed to burn a hole through the bedroom carpet with my little 15w Antex iron when I was a kid after leaving it plugged in! The element failed not long after! Hence why the Antex 25w iron I have had for the last 20 years is a 24v version wired into an old Gent bell transformer with a nice big red indicator lamp!

Comment 1 to 5 of 5
Page: 1

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