Film-Tech Forum ARCHIVE: Strong 61000 Rectifier - Tripped Breaker, Strong Burning Smell

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Posted by Tony Ratcliff (Member # 1196) on 05-23-2014, 10:32 PM:

About 3/4 through the movie the 30amp breaker tripped on my power supply, a Strong 61000, single phase, running a 1000W bulb.
I had noticed when starting the movie that the light took a long time to stabilize - took a few tries to light, was dim at first.
And the light looked a little flicky and dim. But these things have always been an indicator that the bulb was getting weak.
But this time the breaker tripped and there was a very strong electrical burning smell. The rectifier normally gets too hot to touch, but it seemed to be even hotter as well.

I took off the cover and other than a good amount of dust I don't see anything obviously burnt.
After it cooled down I turned the breaker back on to see if the fan is working and it is.
I have not tried to strike the lamp again.

Any ideas where to start looking for a cause????

Thanks!

Posted by Monte L Fullmer (Member # 2797) on 05-23-2014, 11:59 PM:

See if you can find a STRONG 1k-3K switcher rectifier to replace it with.

Either an old black "suitcase" switcher, or the newer compact gray case switcher.

It's on the way out to eventually die on you being so old. Bet the windings are just about toast why the smell and the tripped breaker.

Posted by Tony Ratcliff (Member # 1196) on 05-24-2014, 08:40 AM:

I have not tried striking the lamp again.

Is it safe to try using it again today?

Posted by Dave Macaulay (Member # 813) on 05-24-2014, 09:20 AM:

An "old school" tech told me a story of an owner calling in a panic saying "the rectifier is smoking, what should I do?
His answer... get it an ashtray.

Do not use your rectifier until it's been fixed!!!

1 - this unit should not ever be "too hot to touch" particularly at 1kW. Something is terrifically wrong if it gets that hot.
2 - burning smell says... something is extremely overheating.

Open it up and see what overheated. It should be obvious: burned/charred wire insulation, blackened terminals, transformer or choke with the winding covers charred, or a burnt up contactor. (the "transformer" is actually a real transformer and a big choke, the choke part is closest to the output terminal strip.

If the transformer and choke aren't burned out, then it is repairable. All other parts are available.

Probably the bridge has one or more failed diodes. It can be opened up and they are replaceable. If the bridge fails so that high ripple is delivered to the capacitors and choke, the wires to the capacitors often melt. The choke is pretty much indestructible but can get really really hot in this condition.
The fan and heatsink get clogged - sometimes solidly packed - with dust and grease (popcorn oil fumes) which causes the diodes to overheat, and the unit will get hot without the airflow. If it's been too hot to touch then there's a problem with the airflow!
I keep a diode bridge assembly for quick repair, I'm sure a USA service company would have one for exchange if you don't feel like doing diode replacement (the internal cross wiring takes a powerful soldering iron and some care to avoid overheating the diodes while soldering). If you want mine it's for sale, I'll never need it again.

This rectifier is dead stupid and easily repairable, unless the transformer or choke is damaged (that's the end of it). A switching rectifier uses less power and has a much nicer power factor, but is non-repairable by 99% of techs let alone operators. I would fix and continue using the brute-force 61000 unit.

Posted by Tony Ratcliff (Member # 1196) on 05-24-2014, 10:00 AM:

Dave,

Thanks for the detailed advice!

The rectifier has always gotten very hot to the touch.
But other than the fan going out once, I have not had any trouble from it.
I have been going through bulbs much more quickly the last couple years, but I chalked that up to the poor quality of bulbs nowadays. Could this be a cause of the bulbs going out early?

You say you have a 61000 you'd want to sell??
If so, how much would you want for it.

Tony

Posted by Jim Cassedy (Member # 4115) on 05-24-2014, 10:54 AM:

quote: Monte L Fullmer
See if you can find a STRONG 1k-3K switcher rectifier to replace it with.

I agree with Monte, and as others have said, a rectifier/power supply that's been
running "very very hot", tripping a breaker and emitting a burning smell is
definitely on the way to complete failure,if "that ship hasn't already sailed."

There's almost always several of the newer STRONG 'suitcase' type switching
power supplies available on e-bay. They're very reliable.

I even bought an extra one there just to keep as a spare.

Posted by Tony Ratcliff (Member # 1196) on 05-24-2014, 01:01 PM:

Thanks guys.

Update: I tried it out this morning and it won't strike the lamp. I just get a clicking sound from the lamphouse.

Can you guys give me more details on the "suitcase" power supplies you mention?
I am not sure what model you mean.

Thanks!

Posted by Monte L Fullmer (Member # 2797) on 05-24-2014, 02:02 PM:

STRONG came out with a big black switcher rectifier 62-80000 series in the later 80's, and with its size and design, looked like a 'suitcase'.

One can see this in the warehouse/manuals/power supplies section.

I know of someone who has a few of these suitcases that he pulled from X-90 consoles when some theatres went digital.

quote: Tony Ratcliff
I have been going through bulbs much more quickly the last couple years, but I chalked that up to the poor quality of bulbs nowadays. Could this be a cause of the bulbs going out early?

Hi DC ripple will cause this which means the filtering capacitors could be getting super tired.

Posted by Tony Ratcliff (Member # 1196) on 05-24-2014, 03:06 PM:

Thanks Monte.
I'd be interested in contact info for the person who has these.

Posted by Mark Gulbrandsen (Member # 72) on 05-27-2014, 02:59 PM:

The old black suitcase type Strong switchers are no longer repairable unless it happens to be the three phase bridge rectifier that's fried, that bridge rectifier is still available but that's about the only semiconductor that is...

Only the later black & gray compact switchers(1/2 suitcase size) are still repairable and they are quite easy to fix. I still do repair these supplies at a considerable savings over what Strong charges and I stock a lot of parts for them.

You should open up the rectifier and inspect everything carefully before you attempt to turn it back on. Could be something as simple as a burnt off DC cable or a burnt off AC feed wire. Generally either the bridge rectifier melts down or the switcher transistors and diodes have exploded (literally).

Mark