[Test-Equipment] 8640B parts?

[darrell_gordon at agilent.com]

Hello.  I am new to the group so please excuse a "newbie" question:  Does anyone know of a good source for 8640B parts?  The 5Mhz crystal oscillator on A8 has died on mine and am looking for a replacement.  either oscillator, board, or assembly (in that order).   Curious that the schematic only shows two connections to this oscillator (A8A3Y1), but the module itself has 4 unmarked pins. After removing the oscillator and applying 5v and gnd, there was no sign of life on the output, so I'm assuming it's dead.   (The 8640B works fine with external 5Mhz applied to the reference input).
 
Any sources available??
 
Darrell
Agilent Technologies 
W4CX