HP 8568B Spectrum Analyzer Repair pt. 5 and success!

My HP8568B with YTO unlock error is fixed! Of all things, from a tip from Mark Palmer who watched my previous videos. He told me to adjust R39, and I soon as I touched it, the error disappeared. The pot wiper must not have been making proper contact. That pot controls the DC bias to the FM YTO coil. Well, happy ending thanks to YouTube. Many thanks Mark.