Film-Tech Forum ARCHIVE: Irem , Capacitor Diode Source

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Posted by Marc Jones (Member # 29) on 03-17-2003, 08:41 PM:

Just curious if anyone found these items from any electronic venders like mouser or newark
Thanks

Posted by Mark Gulbrandsen (Member # 72) on 03-17-2003, 09:04 PM:

Other diodes will work ok, but best to get them from your dealer. He will hopefully supply you with factory original parts or possibly even some better diodes. Best to stick with the original type caps in these rectifiers. The relay PCB also fails more often than not.
Mark @ CLACO

Posted by Marc Jones (Member # 29) on 03-17-2003, 10:26 PM:

OK what would be the symtom of when the relay board fails, I currenly have a Xetron XH series lamp with an irem rectifier in the console. there is a little flicker on the screen, I have check all diodes and verified that I have all there phases on the contactor, so I thought maybe replaceing the caps would reduce the ripple or would the relay board help this problem.
Thanks

Posted by Mark Gulbrandsen (Member # 72) on 03-17-2003, 10:38 PM:

The relay board, and associated components supplies the no-load start voltage (about 120 vdc) for a timed period I believe done by a simple RC circuit. If you have slight flicker its very possible you may have an open diode. You'd have to check them all to see if one is bad...its quite easy to do in that rectifier. Because of the star configuration, if one diode opens up they usually still run...but with a slight flicker and slightly lower lamp current. Its best to replace ALL the diodes if you find one bad. Age, and the number of thermal cycles usually determines the life of a diode...lightning strikes also do too. Use a good grade heatsink compound on the new diodes....not the junk from Radio Shack. Also use it sparingly on each diode. With one daub of white heatsink compound and you can almost paint an entire house [Eek!]

With capacitors you usually go by a rated life of 7 years. Most manufacturers detailed specs have graphs that specify life span/vs. operating temperature. I reccommend replacement every 7 years on caps, or earlier if excess ripple or other failures dictate replacement.
Mark @ CLACO

Posted by Marc Jones (Member # 29) on 03-17-2003, 10:47 PM:

Ok let me ask you this one Mark, When the relay board fails, is there a common component that always fails? When this fails is the symtom problem with starting the bulb?
thanks again

Posted by Tim Reed (Member # 137) on 03-18-2003, 12:14 AM:

To answer for Mark, yes, that is a symptom of failure of the relay board. It's a simple matter to replace the whole board as it just plugs in. You have to make sure you have the right board for your size rectifier/lamp combination, too, because there are a couple different values of no-load voltage they're designed for.

Posted by Gordon McLeod (Member # 33) on 03-18-2003, 09:54 AM:

I buy the IR brand diodes and have had few if any failures
I usually buy the 85 amp 600v which is the bigest in that case size to use in Irem and ORC rectifiers

Posted by Marc Jones (Member # 29) on 03-18-2003, 11:18 AM:

Gordon who are you using as your source for diodes
I had found some NTN replacements thru Mouser electronics but they don't have the lead on them.
Thanks

Posted by Chris Markiewicz (Member # 1415) on 03-18-2003, 12:55 PM:

Go for the highest voltage-rated diodes that will fit your rectifier. IREM underspecced the diodes in a lot of their power supplies. Voltage spikes will take those things out. At Keauhou we had constant problems with the 2K diodes and finally upgraded to the same part as the 3K supplies used. End of problem, and it simplified our spare parts inventory.

Posted by Mark Gulbrandsen (Member # 72) on 03-18-2003, 01:00 PM:

"I had found some NTN replacements thru Mouser electronics but they don't have the lead on them."
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If you get em from an Irem daler they will have the leads on them and the insulation. Those are all but immpossible to find "off the shelf" as those leads are custom made by IR for Irem...and others.
Gord is right about the max 85 amp 600 volt rating on that size case. I have modified many Christie 2kw rectifiers for the 4kw diodes...this may also be possible to do in a Iram if there is enough space and clearance around the heatsinks. The 4kw sized diodes never fail.
Mark @ CLACO

Posted by Gordon McLeod (Member # 33) on 03-18-2003, 03:14 PM:

I have found that the IREM diodes are a bit underrated in both current and voltage rateing

Posted by Tim Reed (Member # 137) on 03-18-2003, 03:57 PM:

They are usually pretty good, however, and give little trouble. I'd always suggest going higher on replacements - can't go wrong with that practice. And like Mark said earlier, proper heat conduction is crucial.

Posted by Mark Gulbrandsen (Member # 72) on 03-18-2003, 10:24 PM:

Its also possible to use diodes from the next size up Irem. If you're a bit nervous about them going bad I would suggest that. I have put alot of 4KW diode banks into 2kw, and 2.5kw Christie rectifiers and have never had to return to them for any repair. Believe me that in this sort of rectification use BIGGER is ALOT better. Replacing them all at the same time is also the key to reliability!!
Mark

Posted by Steve Guttag (Member # 268) on 03-18-2003, 11:17 PM:

Actually, the leaded diodes like IREM uses are "off-the-shelf" items...the part number in IR terms are the amperage is the first two digits...so an 85 amp diode will be an 85...if it has a lead it will be 86...if it has a lead and a color coded sheath...it will be an 87... (Red is reverse, Blue is forward).

Steve