Hello!
Further to my previous message, I have found that I can use also HP-54112D input modules (attenuator plus preamplifier assemblies) as they are the same than the HP-54111D units. So both parts would be fine.
Please, check your stash of parts units ;-) and let me know if you can help me.I would buy a complete parts unit of any of the two models.
Thanks!
Best regards and Merry Christmas,
JOSE