DDC Fixed Head Disks

Guy Sotomayor wrote: Helium is a very good thermal conductor but I would suspect that it is used because it is cleaner and dryer than air and nitrogen and truly inert and won't chemically react with the medium. The helium was likely under pressure to reduce the chance of air getting in. Since it can leak out much faster than nitrogen and air, thanks to the physics of helium, the seals and sealing surfaces must be in excellent condition. But no matter how good the seal, helium still leaks out so it needs to be replenished from time to time. If you know anyone with a helium leak detector with a helium probe, maybe you can ask them to find out how much helium leaks out and whether there are any significant leaks. Soapy water or "snoop" will only show relatively massive leaks. A helium leak detector can tell you whether you have to refill the unit every week or every few months and snoop cannot tell you that. Don't put the unit under vacuum though. Might have to pay attention to lubricants, too. There's not many lubricants that don't have volatiles _and_ can tolerate an environment without air. They're out there but like green glue, they're neither expensive nor very obvious. IIRC, helium was used for drum memories, too. Of course, so was the single-head-per-track tech. In the old days, a computer tech was at least as much a mechanic as an electronic tech. Nowadays, it's mostly software. The "mechanical" part is just screws and pulling PC boards. == jd All I ask is a chance to prove that money can't make me happy.