[Brooke48]

I have inherited my father's Canon S-400 8mm cine projector and am digitising his sizeable stock of reels. The projector has not been used for some years and ran fine for the first reel but the lamp blew when I started the second.

The replacement lamp also blew - this time immediately. The manual gives the lamp spec as 8v 50 Watts and this matches the lamps I've used. Using a multimeter, I have measured the voltage across the lamp socket as 10v and assume this is the problem. Can anyone suggest why the voltage could have increased and can this be repaired ?

[klr10]

10v is probably correct, it will drop to 8v under load from the lamp. You were probably just unlucky, these bulbs are very delicate.

[Brooke48]

Thanks for that. A bit risky at £15 - £20 per lamp if they're just going to blow immediately. I'm taking a lot of care with these lamps to avoid fingermarks, shock etc. so I'm wondering if there's anything more I can do to minimise this risk.

Is this slightly unlucky, very unlucky or lottery winning odds ?!

[klr10]

Make sure the connectors for the bulb are clean and tight. Any arcing (sparking) caused by poor connections will often result in the bulb blowing.

[Brooke48]

Will do. I may have come across the cause of the 10 volts - there is a voltage regulator plug on the underside and this was set to 220 volts. I have repostioned this to 240 - the maximum - and found the voltage at the lamp has dropped to 9 volts. As you suggested before, this will probably drop to 8 volts under load. I await delivery of replacement lamps and will give it another go. Thanks for helping out.