PDP-11/34 filter and cable routing questions

John wrote.... Odd, I ran into exactly this dilemma when restoring my 11/34 a few months ago. In my case, I was able to see exactly how it was done before I got the machine due to glue residue and fragments of filter still attached. However I can't tell if this method was factory issue - or if it was just how someone before me years ago did it on this machine. What I can say is that there were apparently different methods over time, as another 11/34 chassis I have clearly wasn't done the same way as the one I recently restored. Not only that, but the two /34 chassis are machined differently with different parts on the front as it relates to this specific question. The one I recently restored, the filter obviously covered the entire front, behind the 1/2 "dec unit" filler panel AND the 11/34 front panel - all one piece. To my own eye, it would seem quite silly/ineffective to cover just the top portion behind the filler panel. The full frontal piece of foam was held in place by three mechanisms. First, there were small strips of velcro (the plastic grabbing fingers you described) horizontally. These appear to have just held it in place while the other fastening mechanisms were put in place, and afterwards to keep it from gapping. Second, there were two flat metal vertical bars in front - one on each side - that bolt to the chassis. Each end of the foam was held in place by being clamped under these bars. There were clear indications of disintegrated filter under these bars and that's the only way it could have gotten there. Lastly, there was some glue residue under the bars as well. I removed the glue residue with goo-gone and decided not to use the glue for the new piece of foam. I bolted the bars down on each side on top of the filter media holding it in place (this means I had to make nice holes in the filter media to allow the bolts to go through without binding up the filter. To do this I used an old throw-away soldering iron. One jab and I had nice perfect hole (cauterized even!) in the media right over the bolt hole. Then into these two bars of metal screwed the DEC filler panel snap-on plastic clips on top and the 11/34 front panel on the bottom. The one part I can't remember for sure is how I routed the front panel cables out from behind the foam. I *THINK* I cut a slight rectangle out of the corner on the bottom right, but I'm not positive. It is also possible I routed them out towards the bottom where the filter media isn't actually attached other than velcro. I can check if you'd like. I just looked on another 11/34 chassis that I have, and it has no such vertical metal bars under which to clamp the filter media. But this one has a LOT of velcro on the sides, top, bottom, and middle. This one obviously just used velcro and the filter media covered the entire front of the chassis, front panel bolted on on top of it. For filter media, I used the light grey foam pieces that are designed to be used in window airconditioners and some dehumidifiers. It is about 1/8 of an inch thick and comes in sheets or sometimes loops. For some other projects like this I was able to find a different air conditioner filter media that is 1/4 inch thick and more rigid. I liked this style better for certain things, but by looking at the old crumbling foam in the /34's I was able to tell that the 1/8 (and more flexible) filter media was the more accurate choice. Hope this helps! Jay West