Film-Tech Forum ARCHIVE: Help! Strong Super 80s

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Posted by David Boyd (Member # 4936) on 12-01-2010, 10:32 AM:

We have a pair of Strong Super 80s on Philips (Norelco) DP70s in our main theatre. Trouble is the light is bad and no-one it seems knows what to do, and thus far there have been three shots at fixing it. We show of course 35mm, but 70mm too, so it needs to be good for both. Presently we have dark corners on both machines even on 35mm, and 70mm is truly awful with a dreadful centre hotspot if you try to fill the corners out. Worse, on the #1 machine the light shape is in fact elliptical running from bottom left to top right. We had a bad fire here about three years ago and at that time I bought (on insurance money!) a new apparently matched pair of reflectors which we have fitted, but still we can't get the light right. We've tried pushing the lamphouses either closer to the gate or farther back but to no avail. I had a similar siutation at the NFT in London, and they have now been replaced with Kinoton - lucky them! I don't have the funds to do that. People tell me they've every faith in Strong Super 80s, and I wish I had, but maybe someone here knows what we're doing wrong, or not doing that we should be. The 'scope screen is 27'1" x 11'6" (fixed height)and the throw is 60'. Thanks in advance!

Posted by Louis Bornwasser (Member # 3063) on 12-01-2010, 10:43 AM:

About that time, I attempted to puchase new reflectors from Strong for the Super 80. 5 in a row were bad from the factory. The issue was improper tension when the potting compound was set. The reflector warped. This should have been obvious upon installation. I am certain that new Strong reflectors are good.

Perhaps your dealer can get a refund for the bad reflectors. louis

Posted by Scott Norwood (Member # 30) on 12-01-2010, 10:57 AM:

I'm sure that Louis is right here, but I'll throw this out: are you using the beam spreaders for 70mm?

Posted by David Boyd (Member # 4936) on 12-01-2010, 11:13 AM:

Thanks guys. Hmm, a "pissed" reflector sounds right enough. I'll see about getting another pair, this is interesting that they may be from a bad batch. I'm not using beam spreaders - I gather they were tried and deemed not to work. Certainly I remember trying them in London and they did not seem to work there either... Cheers.

Posted by Tony Bandiera Jr (Member # 2365) on 12-01-2010, 05:50 PM:

David, I would check the lamphouse-to-aperture distance. From what you are describing it sounds like the lamps are too close to the projector. (Edit: Whoops, Steve was posting as I was and he is correct, the lamps may actually be too FAR from the projector.)

You can safely try to move the entire lamphouse back a little at a time while watching the spot on the screen, through the lens with projector running. (Open the dowser for only a short time and allow the lens to cool by closing the dowser frequently.)

Any resulting gap between the lamp and projector can be closed off with a stub of flex exhaust duct or sheet metal formed to fit.

Posted by Steve Guttag (Member # 268) on 12-01-2010, 05:50 PM:

Wait a minute...Super 80 lamphouses on a 11.5' tall screen!??!? The small lamp for the Super 80 is 3KW. The DP70 doesn't do 3-wing shutters so something doesn't add up. Just how defocused are you on this?

While the reflectors could be part of your problems...it still smacks of alignment issues too (wrong spacing, wrong focus on the lamp, bad anode support alignment, poor reflector to aperture/lens alignment...and possible vignetting of the light just getting it to the projector.

If memory serves... on that lamphouse on a DP70...the lamphouse will not need a "snood" and it will just about hit the "snood" of the DP70...particularly if your lamphouse as the beam-spreader attachment. You definitely need to get your working distance correct. And since you want 70mm capability, it will be closer than for 35mm to get the cone of light large enough at the aperture.

What gets me is that you should really only need about 2KW...you will loose some efficiency with the offset of 35mm Vs 70mm but 2K should still work, 2500-watts tops.

-Steve

Posted by Mark Gulbrandsen (Member # 72) on 12-01-2010, 05:57 PM:

Now that system would make Technicolor 3-D look stunning!!!

Posted by Louis Bornwasser (Member # 3063) on 12-01-2010, 08:45 PM:

Amen! Louis

Posted by Jim Cassedy (Member # 4115) on 12-01-2010, 10:02 PM:

Earlier this year, we also replaced one of our
oldlamphouses with a refurbished Strong Super 80,
which included a new reflector.

When we first threw light on the screen, it looked
awful! I too could not get an even light on the screen.

I've worked with the 80's many times and I KNEW it
was capable of much better performance.

After eliminating every other possibility, we got
our supplier to send us another new reflector and
'presto' - - problem solved! So apparantly, there
must have been a bad run of them at some point and
a few of them are still out there on warehouse
shelves, or wherever.

Posted by Monte L Fullmer (Member # 2797) on 12-02-2010, 02:39 AM:

..drop in Technilight reflectors... with a short gap bulb.

Posted by Pete Naples (Member # 761) on 12-02-2010, 02:43 AM:

I've reworked the support system, such as it is, on Davids lamps, and laser aligned them when the new reflectors went in, they aer still cack.

We tried them at the distance specified in the manual, light was cack.

The distance they are currently sat from the aperture is about the best compromise we could come up with.

Having said all that, No2 is a lot better than No1, which lends weight to the warped reflector theory.

The other thing to bear in mind is that everyone and their great aunt has had a go at these lamps over the last 15 years, we've no way of knowing if the internals of the lamphouse, I'm talking about the mirror support bulkhead, has been played with.

It's a bit like clearing snow here in Dunfermline, as fast as you dig it, more falls out of the skiy!

Posted by Louis Bornwasser (Member # 3063) on 12-02-2010, 09:14 AM:

We rebuild S-80's and X60s all the time. If you assume that your have a good reflector and that working distance is correct, there is nothing left to do except optical alignment and maybe a little touch up on the 2 upper rods. Louis

Posted by David Boyd (Member # 4936) on 12-03-2010, 10:03 AM:

Thanks to everyone who wrote in about this. Hopefully we can have another go at it in the early New Year. Cheers. David.