telemonster
Contributor
Saw this on the Prism2 facebook group -- didn't see it mentioned on here. This is a direct copy/paste from facebook.
AST REBREATHER SENSOR ISSUE
As a number of divers are aware, AST has had issues with some of their sensors not reaching higher PPO2s and reacting slowly resulting in them being voted out by the electronics. And, shortly after the mv in air will drop below specs.
This problem is a result of the lead wool being overly compressed resulting in less surface area for a complete reaction to take place. Each sensor requires a certain amount of lead and surface area in order to produce certain mv and for the expected life of the sensor. When the lead is compressed too much, it impacts both mv output and life span.
If anyone has a bad sensor, it will usually calibrate, but will fail during the dive or several dives later. To date, the sensors with this issue have been with 14Ds, 14d1s, 14D2s, and 14D3s that were built in the July/August time frame.
The problem was due to an new operator (assembly person) compressing the lead because it was easier to place into the shell. AST has retrained personnel and now a gauge must be used to ensure the lead is not compressed more than it should be.
If anyone has a bad sensor, please contact the AST dealer or distributor you purchased them from for replacement. Please provide them with the serial number of the failed sensor.
I’ll try and answer any questions anyone has.
Best regards,
Patrick Duffy
AST REBREATHER SENSOR ISSUE
As a number of divers are aware, AST has had issues with some of their sensors not reaching higher PPO2s and reacting slowly resulting in them being voted out by the electronics. And, shortly after the mv in air will drop below specs.
This problem is a result of the lead wool being overly compressed resulting in less surface area for a complete reaction to take place. Each sensor requires a certain amount of lead and surface area in order to produce certain mv and for the expected life of the sensor. When the lead is compressed too much, it impacts both mv output and life span.
If anyone has a bad sensor, it will usually calibrate, but will fail during the dive or several dives later. To date, the sensors with this issue have been with 14Ds, 14d1s, 14D2s, and 14D3s that were built in the July/August time frame.
The problem was due to an new operator (assembly person) compressing the lead because it was easier to place into the shell. AST has retrained personnel and now a gauge must be used to ensure the lead is not compressed more than it should be.
If anyone has a bad sensor, please contact the AST dealer or distributor you purchased them from for replacement. Please provide them with the serial number of the failed sensor.
I’ll try and answer any questions anyone has.
Best regards,
Patrick Duffy
