May 2001: We have a fix for the intermittent multiport valve alignment problems experienced by some users of McLane Remote Access Samplers (RAS) and Water Transfer Systems (WTS). The problem may also affect belt alignment in Zooplankton Samplers (ZPS), although there have been no reported occurrences.

Please review the paragraphs below and feel free to email or call (508-495-4000) us for additional information. This information applies only to Tattletale 8 Version 1 based systems. TT8 V2 systems are not affected.

Several customers have reported intermittent valve alignment problems. The systems may, for example, work on the bench and then experience problems during a deployment. In some cases they have failed on the bench one day and worked perfectly the next. Until recently, all of these systems always worked perfectly when sent back to McLane for service. Last spring, one system continued to misbehave while in our custody and we were able to identify the source of the problem. There is a design flaw in the circuit that reads the proximity switch used to sense valve position. The circuit normally works despite the flaw. We hypothesize that variations in new production runs of the proximity switch may have made failure more common. Temperature or other environmental factors may also play a role. Since the same circuit is used to read the proximity switch that senses belt position in the ZPS, there is concern for those systems, although there have be no reported problems.

The design flaw is correctable and can be easily applied to existing boards. We will be happy to retrofit your electronics at your convenience (there may be a small fee to cover shipping, no charge if the system is still under warranty). If you wish to install the fix yourself (a pair of 1206 surface mount resistors) just download the illustrated instructions. Email or call (508-495-4000) us if you need assistance or additional information. Resistors will be provided on request.

Remember, the design flaw and the retrofit only affect TT8 V1 based electronics. The flaw is corrected in the new circuitry on TT8 V2 systems. Additionally, TT8 V2 systems use a more reliable optical position sensor.