ST-7 Frost problem

My ST-7 is frosting up.

I took out the dessicant plug, put in the dummy plug, and baked the dessicant for about four and a half hours at 350, like it says. I immediately walked the warm dessicant plug to the camera and replaced it. The O-ring looks good. The plug was still warm when I put it in the camera. Three hours later, I took cooled the camera, took flats, and could still see the frost pattern.

Did I do something wrong? Should I have done something else? Any ideas?

Alex

There's no need to put it back while it's still warm, Alex. It will cool to the touch rapidly. You might want to check to see if the O-ring didn't melt. It's a standard size that you can find at any hardware store should you need to replace it.
Three hours is not long enough for the dessicant to work. Wait at least 12 hours.

dan