Film-Tech Forum ARCHIVE: Xenon power problem

This is topic Xenon power problem in forum Film Handlers' Forum at Film-Tech Forum ARCHIVE.

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Posted by Matt Close (Member # 996) on 04-27-2002, 08:20 AM:

Some good news for anyone who was helping me with my Eprad power supply woes .... (another of our cinemas swapped me there non-working lamphouse and supply for one of my working ones ..... I think I got the wrong end of that deal!) Well, anyway ...I got the it working

However, what size bulb are they supposed to run? We run 2000W lamps here, and it seemed to be really struggling, so I replaced the diodes with much larger ones The leads on the old ones loked 'very' heat-stressed...... The problem I have now is like this :- The lamp strikes ok , then after a few seconds, the amp meter rockets up over 100, so I turn the current down ... down ... down .... so it sits on 70 where we usually run them. According to the meter though, the current is fluctuating +/- 3 amps or so, and this of course is visable on the screen.... Over the first approx 10 minutes of operation, I have to keep winding the current up on the power supply to maintain 70 amps on the meter, eventually almost flat out on the current dial, then it sits there happily.... happily except for the damed fluctuation!!

The xenon lamp just came out of another lamphouse 4 days ago where it exhibited no problems. Also it is only 3 months old.

I am only new to xenon lamps, lamphouses and supplies, so where should I be looking? Is the lamp faulty? Am I just seeing AC ripple? (there is a very slight buzz coming from the choke in the rectifier) Is anyone familiar with the Eprad 47702 power supply? Is asking for 70 amps to run a 2000W lamp too much from a supply rated at 80amps max? Should I use 1600W lamps instead?

Posted by Gordon McLeod (Member # 33) on 04-27-2002, 09:01 AM:

Pat of the current fluctuation is probably from moving the lamp the same as when it is rotated it will be unstable for a while
As for why the current regulation is whacked out on the rectifier that is odd Almost all the ones up here are very stable
Not the current will change on them about 5 amps over 2 hours

Posted by Matt Close (Member # 996) on 04-27-2002, 06:55 PM:

Actually it's fluctuating anywhere up to +/- 6 amps

Posted by Matt Close (Member # 996) on 04-27-2002, 11:20 PM:

(Another post to bump my topic up in the hope someone may read it and have some suggestions) .... The fluctuations on the meter happen right from start-up .... sometimes they will reduce in intensity for just a little while, but then increase again. Any ideas? Should I just replace the lamp?

Posted by Stan Gunn (Member # 554) on 04-29-2002, 05:20 AM:

Make sure the wiper on the variable transformer is makeing good contact, and the coil surface is clean and bright where the wiper runs.

I take it you recieved the circuits.

Stan.

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