Philips XWC121 internals (Repaired)

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.

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Comment 1 to 4 of 4

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Danny

[10 Jan, 2017 at 09:08 PM]

Think mine has the same problem to be honest. Im just going to rip it out and replace it with a 20mm cell as i aint all that keen on the bare boards. The ignitor ive put a case on it from a dead SX72

Kev

[11 Jan, 2017 at 07:58 AM]

So this cell switches the neutral?

RobTDCI

[11 Jan, 2017 at 09:40 AM]

Yes Kev, it switches nuetral.

Slyspark

[11 Jan, 2017 at 06:23 PM]

I gutted one of these last year in order to refit it with the gear required to operate an 18w compact fluorescent. I was surprised to find the neutral switched, seems rather an odd way to do it and I'd have thought massively increases the risk of electric shock if it's still got a connected supply when you re-lamp (assuming you're stupid enough to put your fingers in the lampholder that is).

Comment 1 to 4 of 4

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