Re: Type 502 scope : missing air filter, what gives ?!

Richard Knoppow

Late in this thread and maybe of no interest. When I worked for Hewlett-Packard a very long time ago many instruments had blowers. The usual filter was the aluminum mesh kind coated with an oily material made for that purpose. I don't remember its name but it came in about pint cans with a push pump sprayer on it. The stuff washed off with hot water. From the crap on the filters it must have been fairly effective.
Foam has to be porous something like acoustical foam. Special foam is made for air filters. Many kinds of plastics disintegrate with time, some turn into nasty mush.
As has been stated by others a filter must allow air to flow. Its always an obstruction but should be a minimum obstruction. There are well established methods for measuring the flow rate but I am unaware of any that are simple other than just feeling the air stream.

On 11/15/2018 2:27 PM, Vincent Trouilliez wrote:
Chuck thans for your input... looks like th sis it then... Tek used both the charcoal foam filter, and the mesh filter, on a given scope.. so it's nothing special to the 502 unlike what I thought ! .. and just "bad" luck that every 502 I saw had a missing filter and every non-502 had a metal mesh filter.
But your memories are vivid, and looking at pictures of the 545/A on Tekwiki, confirms what you say !
Richard Knoppow

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