Repairing or cleaning a PA-II

I have just air blasted the unit, two insects fell out (was gonna say bugs but that be misleading) but “laser B” is still not operational. Can I take the unit apart and clean it ? If it is a hardware failure can I send it out to be repaired somewhere?

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Hi @Billyb, taking apart and cleaning a Plantower laser counter is possible. The following link will take you to an online tutorial explaining this process:

The other option would be to look into laser counter replacement. The bottom of the Sensor Maintenance article will explain more.

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I experienced an issue with one of the channels in my PA-II reading way high & that channel getting temporarily downgraded to 0% reliability.

I carefully opened up the sensor (complete disassembly, per the PublicLab tutorial,) cleaned the laser window & sensor carefully with 99% IPA, let it all dry and then re-assembled it.

The sensor then started working perfectly, tracking the other sensor extremely well. I thought everything was fixed. But now the cleaned-up sensor makes random, large excursions that sometimes last for hours – before returning again to normal and close tracking of its partner sensor in the same PA-II housing.

Attached is a screen shot showing this strange on-and-off behavior for the affected sensor.

(Note that the very sharp high spike shown was from someone’s outdoor barbecue, and in fact both sensors also tracked that sudden spike with near-perfect agreement.)

Once the sensor has been cleaned and is tracking fine, what is it that causes these disconcerting, random large departures from normal operation? Why do the anomalies then also self-resolve again, apparently at random?