ECR Title: ECR: CM Board Modifications (ALS)	DCC No: E12xxxxx-vx
Date: 10/12/2012
Requester: Daniel Sigg	Impacted Subsystem(s): ISC
Description of Proposed Change(s): As a result of the one arm test a number of changes need to be propagated to all other ALS end station boards. The common mode boards are described in a wiki. The modifications affect the transfer functions for the laser locking and the cavity locking. It adds low pass filtering to suppress PZT resonances and it fixes a gain in the slow controls readback. As a consequence the previously identical ALS boards are now split into two types: LL (laser locking) and ALS (cavity locking). The actual boards are D040180-E. The changes are described in E1200907-v1.
Reason for Change(s): The transfer functions of the ALS common mode boards had to be modified to reflect reality.
Estimated Cost: total $5k (parts and labor)
Schedule Impact Estimate: None.
Nature of Change (check all that apply): Safety Correct Hardware Correct Documentation	Improve Hardware Improve/clarify Documentation Change Interface Change Requirement
Importance: Desirable for ease of use, maintenance, safety Desirable for improved performance, reliability Essential for performance, reliability Essential for function Essential for safety	Urgency: no urgency desirable by date/event: _Feb 2013____ Essential by date/event: ____________ Immediately (ASAP)
Impacted Hardware (select all that apply): Repair/modify. List part & SNs: ______________________ Scrap & Replace. List part & SNs:_____________________ Installed units? List IFO, part & SNs: _________________ Future units to be built	Impacted Documentation (list all dwgs, design reports, test reports, specifications, etc.): D040180-E, E1200907, T1200477
Disposition (to be completed by Systems Engineering): TRB CCB Approved Additional information required. Define: [Requester re-submits with new information with the same DCC E-number for the ECR but the next version number.] Concurrence by Project Management: (Acknowledged Electronically in DCC) Project Systems Engineer: Dennis Coyne Project Systems Scientist: Peter Fritschel