diff --git a/playbook/shopfloor-setup/gea-shopfloor-cmm/scripts/Backup-CMM.ps1 b/playbook/shopfloor-setup/gea-shopfloor-cmm/scripts/Backup-CMM.ps1
index d2553db..8e14826 100644
--- a/playbook/shopfloor-setup/gea-shopfloor-cmm/scripts/Backup-CMM.ps1
+++ b/playbook/shopfloor-setup/gea-shopfloor-cmm/scripts/Backup-CMM.ps1
@@ -11,23 +11,43 @@ restored by CMM machine-# at imaging.
 
 Run as ADMINISTRATOR on the live CMM. Do NOT run on DODA bays (handled separately).
 
-Output: C:\Logs\CMM\cmm-backup\<CmmId>\
+Output (default): S:\2 WJ Scans Record Retention\backup\cmm\<CmmId>\
           gocmm_backup_<PC>_<ts>.zip
           pcdmis_backup_<PC>_<ver>_<ts>.zip   (one per PC-DMIS version)
           cmm-backup-index.json
+If S: is not mapped/reachable, falls back to C:\Logs\CMM\cmm-backup\<CmmId>\.
 
 Params:
-  -CmmId <id>   e.g. CMM3 - names the folder + index (default: computer name)
-  -OutDir <p>   base output folder (default C:\Logs\CMM\cmm-backup)
+  -CmmId <id>   e.g. CMM3 - names the folder + index. If omitted, the script
+                PROMPTS for it.
+  -OutDir <p>   base output folder (default the S: record-retention path above)
 #>
 param(
     [string]$CmmId,
-    [string]$OutDir = 'C:\Logs\CMM\cmm-backup'
+    [string]$OutDir = 'S:\2 WJ Scans Record Retention\backup\cmm'
 )
 $ErrorActionPreference = 'Continue'
 $here = Split-Path -Parent $MyInvocation.MyCommand.Path
 $ts   = Get-Date -Format 'yyyyMMdd-HHmmss'
-if (-not $CmmId) { $CmmId = $env:COMPUTERNAME }
+
+# Prompt for the CMM number if not passed. It names the backup folder, so we
+# need a real value - loop until non-empty.
+if (-not $CmmId) {
+    while (-not $CmmId) {
+        $CmmId = (Read-Host "Enter the CMM number for this bay (e.g. CMM3)").Trim()
+        if (-not $CmmId) { Write-Host "  CMM number is required." -ForegroundColor Yellow }
+    }
+}
+
+# Default OutDir is on S: (record retention). If S: is not mapped or that base
+# path is unreachable, fall back to a local folder so the backup still runs -
+# the operator can copy it up to S: afterward.
+$fallback = 'C:\Logs\CMM\cmm-backup'
+$baseRoot = Split-Path -Qualifier $OutDir -ErrorAction SilentlyContinue
+if ($baseRoot -and -not (Test-Path "$baseRoot\")) {
+    Write-Host "WARNING: $baseRoot is not reachable (S: not mapped?). Falling back to $fallback" -ForegroundColor Yellow
+    $OutDir = $fallback
+}
 $dest = Join-Path $OutDir $CmmId
 New-Item -ItemType Directory -Path $dest -Force -ErrorAction SilentlyContinue | Out-Null
 $log = Join-Path $dest "cmm-backup-$ts.log"