Before I dive deeply into troubleshooting maybe someone can give me a direction to look into first.
I have a HP 432A with a downward drift. Same problem on all three mounts that I have, a HP 478A, a HP X486A, and a Micronetics TM-400. So I¡¯m pretty sure it¡¯s not the mount! The drift is slight on the 10 mW range but gets quite bad as you go down in ranges. The shunt regulator +7V and -13V outputs seem okay. The meter otherwise is working, the drift is the only problem.
Steve J. Noll, WA6EJO