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I'm searching for a artificial load for an old computer PSU (cheap chinese 400W, only passive PFC) and found in a box a couple of halogen bulbs rated for 12V AC (35W). Tried one of them on the 12V wiring (the yellow one) and the bulb worked for 20-25min without problems - no strobing, no overheat, PSU looked stable for its class (12V rail showed ±0.08-0.15). What can possibly go wrong?

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    \$\begingroup\$ See electronics.stackexchange.com/questions/75330/…. \$\endgroup\$ – Transistor Aug 27 '17 at 19:55
  • \$\begingroup\$ My question is about safety (generally asking what part of the power source-lighting source combo will fail first) \$\endgroup\$ – 1000Gbps Aug 27 '17 at 20:42
  • \$\begingroup\$ And Marco's answer to that question explains that for low voltage lamps there is no difference in lamp lifespan. Note that your title mentions AC lamp powered by DC hence the relevance of that answer. \$\endgroup\$ – Transistor Aug 27 '17 at 20:47
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It'll work just fine.

Note that a bulb with a cold filament has much lower resistance than hot, thus inrush current at turn-on is quite enormous, like 10x rated current.

No trouble for a 400W PSU, but if you try your "35W" bulb on a 35W PSU, most likely it will have trouble starting up.

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  • \$\begingroup\$ That's why I'm using a dimmer for all my lamps - slow start is better for their lifespan \$\endgroup\$ – 1000Gbps Aug 27 '17 at 21:02
  • \$\begingroup\$ Dimmer won't help when building a test load. And yeah, the cold resistance of lamps is not to be overestimated - a 25A(!!!) linear (!!!) bench PSU I have tends to have trouble starting even a 25W H3 car bulb... \$\endgroup\$ – rackandboneman Aug 28 '17 at 0:56
  • \$\begingroup\$ Not using a dimmer for THOSE lamps \$\endgroup\$ – 1000Gbps Aug 28 '17 at 19:11
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    \$\begingroup\$ 25 amps linear? does it have wheels to move it around? \$\endgroup\$ – peufeu Aug 28 '17 at 19:18

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