Does your PortaCount take ages to get above 1000 particles/cc? Is it constantly giving out "Low Particle" warnings?

@ghhughes recently posted a valuable thread on how to clean a low-counting PortaCount, based on @findmeabluebird finding a manual alluding to a way to clean the ever elusive "internal lenses" constantly described in PortaCount 8020 documentation. Since Nitter is having issues these days, this post serves as an alternate discussion area for those unable and unwilling to use the site formerly known as Twitter.

Archive.org link to thread via Nitter

Now if only someone could fabricate the two, circular replacement filters located on the bottom of the PortaCount...

Here's the thread copied again below, this time with full-res images:

I just cleaned the sampling cone in my lowest counting PortaCount. Now it counts higher than my highest. :-)

I followed directions in the Canadian military manual found by findmeabluebird, starting on page 88.

Archive.org link

You might damage your machine trying this.

The instructions were a little unclear. You open the case, and at the back of the unit remove two hex bolts. Then pry the round disk out which is the base of the sampling cone. Leave the post in place, it stays there.

Note the lint I got on the outside of the sampling cone 😬

As per Aaron Collins suggestion, I used an ultrasonic cleaner on the sampling cone. I had lint-free clean room wipes and swabs because I didn't want to clog the tiny port in the cone with fibers from cleaning.

It's really hard to see inside the cone, so I used an "ear cleaning" camera that connects to my phone. These are cheap on Amazon and Temu, and most models let you remove the ear cleaning tips. The camera showed lint in the cone from my "lint-free" swabs I now needed to get out.

I didn't have canned air available (would have been handy), but with the help of the camera I was able to verify the unit was cleaner, and that I finally got the lint from the swabs out using reagent grade alcohol.

• Check the o-ring before reassembly.

I don't plan on doing this on units that are working well lest I make it worse, perhaps by accidentally getting lint in the cone, or who knows what. If I do do it again I'll be sure to have canned air handy, and maybe a stronger, industrial ultrasonic cleaner.

There are a number of things that may cause low counts in a PortaCount 8020/A/M, including a dying laser diode (which not fixable, unfortunately). This should be a last resort, and it might not improve your counts.

If you try this, be sure to have canned air on hand to dust off the sampling cone before re-assembly. I did not, and it made it much harder to insure I wasn't accidentally introducing dust or lint into the sampling cone, which could clog it.