To find out which of you Windows Domain Controller actually is the PDC, execute te following command and check the output:

C:\>nbtstat -a <name of your domaincontroller>

Local Area Connection:
Node IpAddress: [10.20.113.228] Scope Id: []

           NetBIOS Remote Machine Name Table

       Name               Type         Status
    ---------------------------------------------
    <name of your domaincontroller>        <00>  UNIQUE      Registered
    <name of your domain>      <00>  GROUP       Registered
    <name of your domain>      <1C>  GROUP       Registered
    <name of your domaincontroller>        <20>  UNIQUE      Registered
    <name of your domain>      <1B>  UNIQUE      Registered
    <name of your domain>      <1E>  GROUP       Registered
    <name of your domain>      <1D>  UNIQUE      Registered
    ..__MSBROWSE__.<01>  GROUP       Registered

    MAC Address = 00-0E-7F-30-08-30
C:\

The Domain Controller that is the PDC contains the line:
    <name of your domain>      <1B>  UNIQUE      Registered