This is topic Problem with Strong Power Supply in forum Film Handlers' Forum at Film-Tech Forum ARCHIVE.
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Posted by Aaron Sisemore (Member # 145) on 10-07-2002, 01:01 AM:
OK here is the situation:I have a Strong reactance power supply model 78001-1 that is running a 3000W bulb in a Super 80 lamphouse.
About two months or so ago, the lamp would kick in and out in a relatively fixed pattern (run for about 5 min, kick off, kick back on after about 2-3- min, etc.) I narrowed it down to the thermal sensor on the rectifier stack. I replaced the sensor with a spare I had in a parts box, and things were back to normal. Well, today it began to do the exact same thing again. I currently have the sensor jumpered to keep them on screen, and there have been no reports of anything else abnormal happening since then (no overheating, etc). Bulb (Christie CXL30R) is running at approximately 27VDC/100A. Cooling fan is working properly and the airflow is not restricted. I have noticed that the heat sink plates on the rectifier stack are pretty hot to the touch (too hot to touch for more than a fraction of a second) shortly after the unit shuts down. [yes, I cut the 3-phase to it before sticking my hands in it] 
I know they probably do run hot, but is this 'too' hot?
I plan on calling Strong about this in the morning, but figured I would give you all a shot at it first 
-Aaron
Posted by Steve Guttag (Member # 268) on 10-07-2002, 07:47 AM:
I, for one, have always disapproved of running 3KW lamps on DO-5 diodes (85A max)...they do get damn hot. Is your rectifier one of the current ones (FXPS)? I believe they are using much higher current diodes on all of the rectifier sizes. BTW, the thermal sensor may have been defective as well (the one you put on)...check it's rating and use a thermal sensor to see what it really is running.
Steve
------------------
"Old projectionists never die, they just changeover!"
Posted by Jon Bartow (Member # 241) on 10-07-2002, 08:31 AM:
You could allways employ Christie's fix :
put a muffin fan in there to blow a little air across the heat sinks
But seriously, Steve is right, I don't like running the 85 amp diodes in a 3k either. You could try a larger diode, just be careful with the stud size, once you get up to 100 amps most of them have a larger stud, requiring that you drill out the heat sinks which means no going back to the smaller diodes. (not that you would need to)
Posted by Ken Layton (Member # 133) on 10-07-2002, 09:12 AM:
Aaron:You didn't mention the model number of the power supply in question.
Posted by Paul G. Thompson (Member # 655) on 10-07-2002, 12:06 PM:
I agree with Steve.
Posted by Aaron Sisemore (Member # 145) on 10-07-2002, 06:06 PM:
>>You didn't mention the model number of the power supply in question.<<I didn't have that handy when I posted. It is a model 78001-1 reactance power supply.
Changing the heat sensor yet again failed to correct the problem.
-Aaron
Posted by Rick Long Jr (Member # 541) on 10-07-2002, 08:54 PM:
Try tightening the threaded rod that sandwitches the plates of the stack together. Not the nuts that secure it to the mount, but the two inner nuts. I have found when rebuilding this type of stack that if the plates aren't secured tight enough, it will cause problems. In some cases I have had to gently grind the plates as arcing had been occurring between them and the pieces of metal that the cables connect to. Te whole thing relies on the threaded rod being tight to conduct properly. Hope this helps.
Posted by Mark Gulbrandsen (Member # 72) on 10-07-2002, 09:36 PM:
I've had this same problem. Weather you guys lke those diodes in there is irrelevant as there are alot of these out there. Check the wiring that is on the diode stem connections. I'd be willing to bet that it is burnt up. I have seen this happen numerous times. If this is the problem and youahev to replace the wiring by taking the thing all apart also replace all the diodes at the same time. It IS ALOT of work to properly repair these stacks. Also, if in doubt, just replace all the diodes all together. One or two of them may be experiencing thermal failure where they open up when they get hot. If I remember there is a large round fan in this unit....like the fan on the plenum of a Super Highlite console. Be sure this fan is always going full tilt, or these 85 amp diodes will turn to cinders!! Unfortunately there is not really much room to mount larger devices on this unit. After I re-wired several of these stacks and replaced the diodes they ran trouble free for over a decade till the theatre closed down.
Mark @ CLACO
Posted by Shaun Flichel (Member # 1435) on 10-11-2002, 11:22 AM:
I would personally check the running temp out on the stack, its possible that the replacements you recieved are too low of temp. And yes while in there, check all connections for tightness and cleanliness. Always remember the charged caps in there.