Specs for replacement heat shields for lamp house?

[Ryan Gallagher]

It's been on my wanted list for a while to replace the heat shield glass in the Strong Super 80 lamphouse. The only sources I've found have been crazy expensive for an OEM part.

The late John had a couple but passed them on before I could convince anyone to spend money.

I've been looking at the Borosilicate Hot Mirror specs provided by this manufacturer. Would such a 3rd party part be appropriate?
https://www.knightoptical.com/stock/...t-mirrors.html

(Hot Mirrors are the term for those that pass visible and UV, but reflect NIR and IR).

I need to get the calipers out to verify if any of their stock sizes are correct, but I presume they might be able to do a custom diameter too.

Do you vaunted cinema techs have any sources you already use for such things?

[Ryan Gallagher]

I was also considering Rosco, who has a Borofloat dichroic IR/UV hot mirror filter, which can be done in custom sizes too.
https://us.rosco.com/en/product/iruv-filter

Their No. 8000 and No. 8100 product are very similar but perhaps have different transmission curves?

https://www.gobosource.com/gos/rosco...er-p-3636.html

https://www.gobosource.com/gos/rosco...or-p-3916.html

I guess is reflecting UV something that would have been true of the OEM part, the KnightOptical ones pass UV, where as the Rosco ones say they reflect it.

[Mark Gulbrandsen]

At 1.75mm, those both seem awfully thin! Most of the projector heat filters seemed like they were 3mm to 5mm thickness. I'd call Rosco, not Gobo Source, and discuss it with them before you buy... And also remember... You need to reflect the IR to something in the lamp house that will absorb the heat. You can't just let the IR hit any place in the lamp house. I have yet to see any lamp house with heat filters reflect straight back in. Even the ORC-1000 had split heat filters on the front that angled the reflected IR at both sides of the of the housing.

[Mark Gulbrandsen]

[Ryan Gallagher]

At 1.75mm, those both seem awfully thin! Most of the projector heat filters seemed like they were 3mm to 5mm thickness. I'd call Rosco, not Gobo Source, and discuss it with them before you buy... And also remember... You need to reflect the IR to something in the lamp house that will absorb the heat. You can't just let the IR hit any place in the lamp house. I have yet to see any lamp house with heat filters reflect straight back in. Even the ORC-1000 had split heat filters on the front that angled the reflected IR at both sides of the of the housing.

Yes thickness is a concern too, would want to hear from them about thermal tolerances before I went thinner than factory.

in the Super 80 houses that insert is designed to have the glass sit at a slight angle in the holder, to avoid reflecting the heat directly back at the lamp, but as for suitable area to have it hit instead, not so much. It is not like the strong spotlight houses that place it at a full 45deg to the beam.

[Mark Gulbrandsen]

See the raised surface when the door is open? There is also one on the other side. Pretty sure that is where the heat filter is supposed to aim to. And I don't remember anything on the top or bottom, but it's been a few years since I last worked with them, and that would have been to remove them for conversion. Also, don't forget that the lamps were in a super trooper reversed from the norm. Steve Guttag would know about the Super 80 heat filter for sure.

[Ryan Gallagher]

See the raised surface when the door is open? There is also one on the other side. Pretty sure that is where the heat filter is supposed to aim to. And I don't remember anything on the top or bottom, but it's been a few years since I last worked with them, and that would have been to remove them for conversion. Also, don't forget that the lamps were in a super trooper reversed from the norm. Steve Guttag would know about the Super 80 heat filter for sure.

I've only got how the glass sits in my holders for reference, and they are angled down within the play within the ring holder, rather than left or right, but that could have shifted since they were manufactured by previous operators.

One was already cracked when I joined this booth (probably inserted backwards at some point), so it's a bit finnicky to keep an intended angle in the ring mount. And their coatings have probably degraded too. Hence this journey to replace them.

I could see those double wall sections as maybe being IR absorption targets, but it could also just be a buffer to keep the lamphouse beyond the reflector a bit cooler to the touch (effectively an IR absorber but not specifically for the filter to aim at). The amount you can angle the glass does not seem like it would be enough to actually aim for those, in any meaningful way. But left, right, or up might be better than down, no electronics on those surfaces.

To be clear, I'm talking about the OPTIONAL heat filter part (40939) that can be placed in the 70mm spreader lens slot when in 35mm mode. So they are definitely optional, but we are lamped at 4K so they would be nice to rejuvenate and continue their service life. Unfortunately no clear description in manual of how they would have been angled from the factory (within the very limited range to change that angle).

70mm Kit.png

Amusingly one thing I do have a full NIB spares of is the lens holder mount and snoods. But just the one set of spreader lenses and heat filters. And it has been discussed previously moving away from the spreader lens and adjusting the working distance instead. Having an alternate set of snoods may be handy for that approach eventually.

[Mark Gulbrandsen]

Just make sure the IR coating faces the xenon lamp. The other way around will allow the UV to pass twice through the glass. Sometimes people don't know which side is which nor the result of doing that.

[Mark Gulbrandsen]

Another thought is to call Troy James at Strong in Omaha, and see if they have the factory filters. They just might, or he may have you call the Spot Light Division. They still build and sell all the spotlights.