Film-Tech Forum ARCHIVE: Relay-like snap/clunk sound coming from power supply IREM Xetron N3-X75/95

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Posted by Tony Ratcliff (Member # 1196) on 11-13-2014, 03:46 PM:

I have a IREM Xetron N3-X75/95 power supply with a 2000 watt bulb in a Super-Lumex lamphouse.
When the bulb first strikes, a relay-like snapping/clunking noise comes from the power supply. It doesn't always do it. Sometimes it does it several times.
It also happens once or twice during the show.
I don't see any visual affect on the screen, and the amps are steady at 80 on the lamphouse.

It is a very different noise than like the ignitor with a hard-striking bulb. It is a heavier noise.

What could be the cause of this noise?

Thanks!

Posted by Edgar Prass (Member # 7558) on 11-14-2014, 12:54 AM:

Sounds like the automatic fuse on my Videvox X3-140 rectifier. It pops out and back on a fraction of a second later. But the lamp also flickers strongly or goes out when that happens. Mine also does it several times mostly. A good kick is a temporary fix. Took that thing apart, checked everything, did find some problems and solved them, but didn't get rid of the fuse clunking. Solution was to get another rectifier.

Posted by Monte L Fullmer (Member # 2797) on 11-14-2014, 08:47 PM:

Bet you got a 3 phase contactor relay getting ready to fail. The contact points are prob all but burnt due to age.

Posted by Tony Ratcliff (Member # 1196) on 11-15-2014, 12:36 PM:

How hard is it to change the contact relays?
Would I still be able to get new ones for this rectifier?

I haven't taken the cover off the rectifier yet, but I have been able to watch thru the vents when it is happening and I can see sparks. But I can't tell exactly where they come from.

Posted by Louis Bornwasser (Member # 3063) on 11-15-2014, 08:18 PM:

Tony: remove wheel and top cover.

Posted by Steve Guttag (Member # 268) on 11-16-2014, 02:01 AM:

Irem uses ABB contactors. They are 4-pole type so that one can wire up the system as a self-latching hold circuit. Most all installs in the US don't take advantage of that feature and use either the lamphouse or automation to hold the contactor in so you can replace the ABB with a lower cost 3-pole contactor, if desired (and of a more easily obtained, lower cost brand).

If you go with an ABB, we have found that IREM was a bit optimistic in their current ratings for them in countries with 120/208 power. The contactors would fail due to excessive current so we generally upped the rating when we replaced them so we didn't have to revisit the problem again later. Making sure the wires were securely tightened on the contactor is a must too.

The other relay in an IREM of that vintage is the "RA" relay (in later units it was called the A1 relay, I believe). It is used to keep inrush current down and allow by bypassing the main filter capacitor(s) until the lamp strikes. Once the lamp strikes, the voltage drops, the relay drops and the main capacitors are on line...if that RA relay fails, you can get a situation where the lamp strikes and immediately drops out since the main filters may not be coming on line. So there is another place where you could see sparks too.