HP 8112A Operating, Programming And Servicing Manual page 166

9-14 Adjustment Procedures
14. On the oscilloscope press (s] and adjust A2R8 for
10 ns f 0.2 ns at 50% of amplitude. See Figure 9-5.
15. Alter HP 8112A WID to 99.9 ns.
16. Adjust the low range end with A2R59 for 101 ns f0.2 ns.
17. Repeat previous six steps and re-adjust if necessary.
18. Alter HP 8112A WID to 50 ns.
19. Check that Min. width is 50 ns f 2ns.