Someone help me troubleshoot what's going on here, because I'm stumped; I inherited a literally-brand-new-except-for-the-box Thomas Duplex, and after going over the thing with a fine-toothed comb I'm still having issues with it burning the paper during a very basic eight-minute coin test.

I'm not kidding when I say that the safelight is new; it doesn't have a single scratch on it. In fact, the only thing that needed replacement/rebuilding were the old gelatin filters that were crinkled and thoroughly useless, which is expected with these lights. I rebuilt the inner filters by using the factory glass on the outside and a piece of 50% transmission diffusion plastic on the inside, with the suggested #19 Fire gel sandwiched between the two. For the outer filters, I used a #27 Medium Red between two pieces of factory glass. I used a black vinyl tape to secure the glass and plastic plates together; it works pretty well.

After rebuilding the filters I tested the safelight and got a light burning of the paper in less than a minute's time with the outer vanes slightly open; I used a CD as a poor man's prism and found that there was a faint band of green light making its way either through or around the #19 inner filter. This green band was also present without the filter in place, although it was much stronger and joined by some blue/purple stuff; with the outer vanes closed there was nothing except the yellow/orange/red spectrum to be seen. So, I tried a second test with the vanes fully closed and got exactly the same results.

At this point I was confused because there should be no way that any paper-exposing light could be making it's way through the filters, so I chalked it up to light leakage in he housing and went over all of the safelight's seams with black tape. After that, I taped the inner filters in place - I found a couple of spots where light could easily leak around the filter - and tried a third test with the outer vanes slightly open again. Same results; the one-minute coin silhouette was easily visible.

In a slight bit of desperation I taped the outer vanes down to prevent any and all chances of light leakage, and I ran a fourth test...and got the same results again. I've got no light leaks, no light skipping around the filters, so it seems that the only thing that could be happening is that the filters themselves are...well, not filtering. I find this hard to believe because people have a lot of success with rebuilding Thomas filters with the #19 and #27 gels, but I don't know what else it could be.

Anyone got any thoughts that might help me out, here? Am I doing something wrong that I don't know about?