I have a few DEC RL02 drives, and a Data General drive that uses a pack that appears physically identical to the RL02 packs other than a different sector pulse ring. I haven't begun the process of bringing any of them up yet, but I've removed the air filter from the Data General drive to look at it. It looks like a standard style of HEPA filter, with filter media zigzagged around wavy aluminum spacer plates and then mounted in a plastic box. It looks quite gray on the input side, and he label suggests it was last replaced in the mid to late 1980s. I assume that NOS filters for these drives aren't just laying about in piles, and even if they are, a time will come when there aren't any spares to be found. Thus, I'm interested in what it would take to overhaul existing filters and/or fabricate new ones from scratch. First of all, I assume that it's not practical to clean the existing filter media very thoroughly. If I'm mistaken, then I'd like to know that. It seems to me that I should be able to rebuild a filter like the one in my DG drive assuming that A) I can get it apart without breaking the housing (may not be possible if the edges of the media is strongly glued to the housing?), and B) I can obtain suitable bulk HEPA filter cloth to use. Even if the housing can't be disassembled nondestructively, I might be able to reuse the aluminum spacer plates at least. By the same token, it should be possible to construct new filters from scratch as long as the bulk HEPA filter cloth is available. So, what have other folks already done in this area? Are there suppliers of bulk HEPA filter cloth who would sell in the small quantities that a hobbyist would need? Maybe suitable filter media can be harvested from off-the-shelf items like automotive air filters? -- Mark J. Blair, NF6X <nf6x at nf6x.net> http://www.nf6x.net/