PAR 64 Misbehaving

[jmabray]

No, this is just plain wrong. The 120V unit will have a much lower resistance than the 240V unit. The result is that the lopsided resistive divider formed by the series combination will mean that a much higher proportion of the 240V will appear across the 240V lamp, hence it will be brighter.

Yep you're absolutely right. I forgot about it being in series.

My mistake.

 

[JD]

Related note- Series setups can be real tricky. Used them all the time with ACL's (four 28 volt lamps.) All lamps tend to vary a bit from batch to batch, and across the life of the lamp. It's always a good idea to start with new lamps from the same batch and mark them as a set to be used together. Any variance will put a greater stress on the lamp with the higher resistance. One other problem happens when an old lamp flashes over, many times you will lose both lamps! Good luck, and nice to hear you are starting to have access to the 220 volt lamps.