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Topic: Problem with Strong Power Supply

Aaron Sisemore
Flaming Ribs beat Reeses Peanut Butter Cups any day!

Posts: 3061
From: Rockwall TX USA
Registered: Sep 1999

posted 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

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Steve Guttag
We forgot the crackers Gromit!!!

Posts: 12814
From: Annapolis, MD
Registered: Dec 1999

posted 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!"

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Jon Bartow
Master Film Handler

Posts: 287
From: Massachusetts
Registered: Nov 1999

posted 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)

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Ken Layton
Phenomenal Film Handler

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

posted 10-07-2002 09:12 AM

Aaron:

You didn't mention the model number of the power supply in question.

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Paul G. Thompson
The Weenie Man

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

posted 10-07-2002 12:06 PM

I agree with Steve.

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Aaron Sisemore
Flaming Ribs beat Reeses Peanut Butter Cups any day!

Posts: 3061
From: Rockwall TX USA
Registered: Sep 1999

posted 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

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Rick Long Jr
Expert Film Handler

Posts: 211
From: Toronto, Canada
Registered: Jul 2000

posted 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.

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Mark Gulbrandsen
Resident Trollmaster

Posts: 16657
From: Music City
Registered: Jun 99

posted 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

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Shaun Flichel
Film Handler

Posts: 42
From: Regina, Sask., Canada
Registered: Sep 2002

posted 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.

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