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Author Topic: ORC diode issue Richard May Phenomenal Film Handler Posts: 1057 From: Floral Park, NY USA Registered: Aug 2004 posted 10-04-2011 06:11 PM                     Really strang. I have never had this happen before. ORC 1600 watt console. I had a diode short. I changed it. A few weeks later, one of the wires burnt off the contactor. 2 weeks after that, the same diode shoted AND the other diode on that plate was open. Now I changed all 4 diodes. Last night the same diode shorted again for the 3rd time. Amps are 69. Voltage is around 22. 120VAC on each leg coming in after the contactor. All connections seem tight. The plate which holds the diodes is clean. Any ideas?  |  IP: Logged Mark Gulbrandsen Resident Trollmaster Posts: 16657 From: Music City Registered: Jun 99 posted 10-04-2011 06:29 PM                     Intermittent or clogged cooling fan...? Is this leg of the rectifier on a high leg of three phase AC as measured to neutral....? Bad transformer winding....? I've seen the area where the connecting wires are attached to the heatsinks oxidize and cause excessive ripple and slightly varying current.  |  IP: Logged Richard May Phenomenal Film Handler Posts: 1057 From: Floral Park, NY USA Registered: Aug 2004 posted 10-04-2011 07:01 PM                     Cooling fan is running perfectly. Felt very free. 123.1 VAC on all 3 legs in the panel. I was wondering about where the wires bolt onto the plate myself. Even the diodes themselves. I was thinking about drilling new holes for them. Maybe I'll do it for the wires also.  |  IP: Logged Tony Bandiera Jr Film God Posts: 3067 From: Moreland Idaho Registered: Apr 2004 posted 10-04-2011 11:22 PM                     Richard, did you use silicone heatsink grease on the diodes? VERY important to use it or the new diodes will burn up fast. Also, ALWAYS change at least ALL of the same-polarity diodes as a set! (When one blows it can weaken or damage the others of the same polarity.) I would change all diodes on both positive and negative sides to be safe, remembering the heatsink grease.  |  IP: Logged Richard May Phenomenal Film Handler Posts: 1057 From: Floral Park, NY USA Registered: Aug 2004 posted 10-05-2011 05:05 AM                     Yep. Used the grease and after it blew the second time, I changed all 4 diodes.  |  IP: Logged Steve Guttag We forgot the crackers Gromit!!! Posts: 12814 From: Annapolis, MD Registered: Dec 1999 posted 10-05-2011 06:45 AM                     If you can, measure the current on all four diodes to see if one is being stressed more than the others...likewise, measure the current of the AC coming in...the voltage rarely tells a good enough story. -Steve  |  IP: Logged Bruce Hansen Jedi Master Film Handler Posts: 847 From: Stone Mountain, GA, USA Registered: Dec 1999 posted 10-05-2011 05:03 PM                     Do not use too much heat sink grease. It is there only to fill the microscopic voids in the metal. Too much grease will hurt heat transfer.  |  IP: Logged Tony Bandiera Jr Film God Posts: 3067 From: Moreland Idaho Registered: Apr 2004 posted 10-08-2011 08:17 PM                     Good point Bruce. Of course the best solution is to get rid of that ORC junk in the first place. But not always the practical one.  |  IP: Logged

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