Film-Tech Forum ARCHIVE: Switching Rectifier Failures

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Topic: Switching Rectifier Failures

Rick Long
Jedi Master Film Handler

Posts: 759
From: Toronto, Ontario, Canada
Registered: Nov 1999

posted 04-08-2001 01:55 AM

For the past few years, new equipment has been coming in equipped with switching rectifiers.

Unfortunately, we have had a higher-than-average failure rate with these things.

Fortunately, they are a lot lighter than their reactive-type counterparts, as simply carrying around a pocketfull of diodes is no longer the answer to getting the rectifier up and running again. It is usually necessary to change out the entire rectifier.

I am curious as to your experience with these types of rectifiers, and also if you do the repairs in your own shop or send them back to the manufacturer.

Thanks, in advance, for your input.

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Paul G. Thompson
The Weenie Man

Posts: 4718
From: Mount Vernon WA USA
Registered: Nov 2000

posted 04-08-2001 04:34 AM

I don't know what might be causing your problem, as there is not enough information as what the problem might be.

But I don't know anybody in their right mind would even want to repair those things in the field.

I temporarly replace them with a simple standard rectifier, and send the switcher back on a repair-exchange basis. It is very cost effective.

However, I only had one fail.

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Ken Layton
Phenomenal Film Handler

Posts: 1452
From: Olympia, Wash. USA
Registered: Sep 1999

posted 04-08-2001 09:48 AM

Mostly the power MOSFET transistors fail (either by shorting or going open---they are static sensitive). Keep a few of those handy for do-it-yourself repairs.

I've seen some switching supplies that had either the input varistors or the .47 mfd @ 250 volt input capacitors SHORTED!

Sending the power supply back to the factory can sometimes take a month or more to get it back---and there's no guarantee that it will work when you get it back either.

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Randy Stankey
Film God

Posts: 6539
From: Erie, Pennsylvania
Registered: Jun 99

posted 04-08-2001 05:02 PM

My boss tells me the reason why they call them "switching" rectifiers is because you will always be "switching" them out!

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John T. Mellor
Film Handler

Posts: 52
From: Htafield, Pennsylvania, USA
Registered: May 2000

posted 04-08-2001 10:43 PM

Some of the problems come from the ignighter Strong is using dc ingnighters and I have switched them out at a22 plex I service at least two times on each console and the theater is less than two years old. The ignighter takes to long to build a charge to ignight the bulb and the switcher then quits . You may want to call strong and see what they have to say
John

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Francis Casey
Film Handler

Posts: 44
From: Saint John, NB, Canada
Registered: Jun 2000

posted 04-08-2001 11:04 PM

We have a lot of switchers in our circuit mostly in newer Strong consoles . We have probably had about 8 go out in the last 3 or 4 years .We just ship them back to strong .Every new multiplex we build has a spare switcher or two in some cases .Some are of the hard wired type and others use the mil style connector . About 2/3 are 2-3kw units and the rest are 4-5kw . We have one 7k in use at our Imax for 35mm presentations (it fills the entire 70foot width in flat and scope .
Francis

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Richard Tucker
Film Handler

Posts: 15
From: Austin, TX, USA
Registered: Apr 2001

posted 04-09-2001 12:36 AM

I have had good luck fixing the older-style hard-wired switchers. Sometimes it is a burned wire or bad connection which is obvious as soon as you remove the cover. Sometimes just the fan is clogged, causing the thermals to cut out. One of them had a bad contactor which was sticky. I simply disassembled the contactor and cleaned it . (Turned out they had a roof leak right over the rectifier. Amazing they didn't burn down the building.) The newer style have LED's to supposedly tell you what is wrong, but that doesn't mean they are easier to repair in the field. However, as a rule of thumb I never send one back until I at least open it up for a look.

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