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This is my first post here.

My wife uses a makeup mirror which has 10 x BA9s in series. Each lamp is 3W 24V and since we are in Europe they run on AC 230V nominally (reading off a multimeter is sometimes 243V and even 248V).

A few months ago one of the original bulbs burnt out and the only local replacement I found were 24V 4W BA9S. Now every 4-5 weeks the 4W bulb burns out. I have marked the replaced bulb and it is always the one which burns out.

I thought of replacing all ten incandescent lamps with 24V LEDs from aliexpress. The ones I found are 2W and are meant to be used in vehicles.

My question is, would directly replacing the incandescent bulbs with LEDs lead to a worse situation if one of the SMD LEDs burns out? Can I add some sort of resistor to the 4W incandescent so that the bulb voltage is somehow limited when the makeup mirror is switched on?

Thank you for any help.

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2 Answers 2

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Probably worse If the LEDs are only DC, and just as bad if AC in series which is non-linear.

Now the 4W lights probably are enclosed so they get hotter and reduce life from 3000h by 50% for every 10’C rise above open ambient. A Triac dimmer could solve that as well as a tiny low speed fan. You could use 12V stripLED cut down to size and powered by 12Vdc 1A

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  • \$\begingroup\$ Thank you for the quick reply. I'm afraid that adding a fan is out of the question as the space is very limited and as you rightly pointed out - enclosed. The LED strip is something I have thought about and will definitely look into. \$\endgroup\$
    – salvu
    Commented May 1, 2018 at 14:12
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Instead of using 24V lamps I would use 28V lamps if you stick with incandescent. #1873 comes into mind. But yes you can get ac rated led bulbs. and i would use the ones with the built in current limiting if you go that direction. They will state a wide range of operation (6 Volt-28 Volt AC/DC I've seen) but they cost quite a bit more (around 4GBP)

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  • \$\begingroup\$ Wow. 4GBP each would mean the lamps would probably cost more than a new complete mirror :-). I'll either try to source the original Babyliss lamps or else try to modify and use an led strip off a power supply. Thanks. \$\endgroup\$
    – salvu
    Commented May 1, 2018 at 14:24
  • \$\begingroup\$ #1873 bulbs are not that expensive. And I would go 28V rating so that there is some surge headroom. \$\endgroup\$
    – drtechno
    Commented May 1, 2018 at 14:34
  • \$\begingroup\$ I have checked the #1873 bulbs out but they are rated at 5.6W each at 28V. The makeup mirror has a maximum rating label of 30W. Would the increase in wattage exceed this maximum rating? I know the bulbs are 28V so they'll be operating at less than their maximum but how do I work it out? Using P = VI? Thanks. \$\endgroup\$
    – salvu
    Commented May 5, 2018 at 17:48
  • \$\begingroup\$ The wattage rating is only a marginal increase (4.8W) I doubt it would make any difference. because overall, 4W @240V is 16.667 mA and 4.8W@240V is 20mA . . \$\endgroup\$
    – drtechno
    Commented May 11, 2018 at 14:29

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