This is topic HELP! Strong Power Supply Troubles! in forum Film Handlers' Forum at Film-Tech Forum ARCHIVE.
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Posted by Aaron Sisemore (Member # 145) on 08-29-2001, 09:19 PM:
OK, Here is the latest problem I am having to deal with:The lamp in Fortuna #1 is going intermittent on the operators there. It apparently will run normally for about an hour and a half, then it will shut off, remain off for between 1 min and 15 min(this time period is apparently the same every time) and then just turn back on and run for a while longer, and repeat the off-on process. Heres the stats:
Strong Super-80 lamphouse with Osram 4000W bulb (bulb has approximately 300 hrs on it and does not flicker and strikes easily).
Strong [non-switching] power supply model 78002-01.
Things I have already had them do (This theatre is a 4-hour drive from me and i wanted to get as many of the 'duh' things eliminated before making the trek):
-This problem is occurring both in automation mode and in manual override (ruling out an automation problem)
-The cooling fan is running at full speed, and is running when the lamp quits.
-When the lamp is running, all current and voltage readings are nominal.
-The inside of the power supply and the vents on the sides of the supply have just been cleaned out to maximize airflow through it for good cooling. They report very good airflow through the power supply case.
-I asked if there were any reports of smoke or any smells. One projectionist did say that he smelled a 'burning plasticky smell' when it cut out on him this weekend, however he reported about an hour ago that he cannot smell anything out of the ordinary now.
I have not as of this writing had them check the lampohouse blower, and there is the possibility of the blower vane switch causing this problem, but the fact that it will run fine for an hour and a half before cutting out has me puzzled. This I will be checking with them ASAP.
-I also do not know if the contactor is remaining closed when the lamp quits, this also will be checked out tonight if possible.
Any help, as usual would be greatly appreciated.
Aaron
Posted by Will Kutler (Member # 770) on 08-29-2001, 09:33 PM:
First, do a visual inspection of all the wiring. See if wires and terminals may be touching or arcing resulting in a short. Plastic burning smell could be a bad relay or switch. What about automation relays? Might as well use your multimeter to check the transformer.
Posted by Gordon McLeod (Member # 33) on 08-29-2001, 09:52 PM:
There is usually a thermal cutout switch on the heatsink of the stack if the stak doesn't appear to be getting to hot then try shorting it out and see if the problem goes away and if so the problem is found
Posted by Aaron Sisemore (Member # 145) on 08-29-2001, 10:07 PM:
it is looking like a trip up there is in order... 
-Aaron
Posted by Adam Martin (Member # 641) on 08-29-2001, 10:21 PM:
I agree with Gordon. I've had to replace temp switches in Strongs before. Make sure you get them all ... Some Strongs have two switches on the heatsink. They're little round flat things about the size of a dime.Of course, swapping out the stack and heatsink (with switches attached) worked just as well. 
Posted by Ken Layton (Member # 133) on 08-29-2001, 10:33 PM:
You didn't mention the model of the power supply. If it's a high reactance type, how hot is it getting in the booth???? If it's too hot in the booth, hot air will be sucked INTO the power supply and trip the thermal cutout switches on the heat sink. During the summer months, some theaters I know take the cover off the power supply and set a desk fan to blow directly into the power supply to keep it cool.Of course these cheap thermal cutout switches have been known to go bad as do the microswitches on the lamphouse bulb cooling fan.
If it's a switching power supply it could be loose DC leads on the terminal block burning up or a bad pc board. If the pc board in the power supply is bad, you could try to fix it yourself (if you know how to repair switching regulator supplies) or you'll have to get a loaner and send that one back to Strong.
Posted by Greg Pauley (Member # 503) on 08-29-2001, 10:49 PM:
Sounds like a heat problem and the power supply is shutting down until the temperature drops. I've had to add an additional fan (push and pull) on a few older strongs in locations where the booth is poorly cooled. If the power supply is located in a console you might want to have the operator temporary take off the access door in order to circulate the air. I would have the operator place a fan on the power supply for a couple of days and see if the problem continues before you make a trip.
Posted by Rick Long (Member # 213) on 08-29-2001, 11:01 PM:
I think we're all agreed it's the thermal. Just cause they brush out the intake grill (maybe with the fan running) doesn't mean the bridge aint covered with enough dust bunnies to make a small dog out of. Depending on the capabilities of the staff, I have often got them to take an aligator clip to short out the thermal for a day or two until I can arrange a trip to the place. Ocassionally, taking the top cover off the rectifier helps too (as long as the idiots dont fall into it).The thermal switch, if memory serves, is an 88118, same as the one used in the smaller 61000 series.
If it is the thermal, and they are in the booth at the time, they should hear the contactor kick out, and in again when it re-starts. (Of course, I know you already knew that!).
Posted by Aaron Sisemore (Member # 145) on 08-30-2001, 08:29 PM:
I have had the electrician doing the wiring for the additions in Fortuna bypass the thermal sensors for me today. We will see if that is the problem.Or is it? I have been told that after the first show last night had the problem occur twice, the following two shows ran without a single lamp outage! Maybe there is something else?
If the problem continues with the sensors bypassed, next up is the blower vane switch on the lamphouse, followed by the contactor.
Aaron
Posted by Ken Layton (Member # 133) on 08-31-2001, 12:23 AM:
Some theaters put a twist-lock connector on the end of the power supply's power cord and sometimes the twist lock connector burns up (usually the female section burns first). Be sure to check that, too.
Posted by Mark Gulbrandsen (Member # 72) on 08-31-2001, 11:20 AM:
If this is the large square Strong 3 to 4kw supply I have had troubles with the wiring that runs between the diodes and lugs on the heatsink assembly burning up. You have to look real close with a bright light to see it. Seems like they used too small of wire on them to me and I always replace it with abit larger wire and none of them ever failed again. I have had this happen several times and each time it was the wires on the heatsink that had failed.
MArk @ GTS
Posted by Aaron Sisemore (Member # 145) on 08-31-2001, 11:52 AM:
Well, all shows ran yesterday without any shutdowns. Hopefully this holds until I can get there on my scheduled service day ( in about 2 weeks)Thanks again, i will remember all the suggestions when I finally get up there.
Aaron
Posted by Rick Long (Member # 213) on 09-01-2001, 05:24 PM:
BTW, I have found that once the thermal sensors have "triggered" they tend to become much more sensitive. If that was the cause, I suggest replacing it.