Cleaning, Checking and Inventory

Parent Category: Stories Category: VAX 11/750: The Resurrection of a Comet Written by UlliH
As soon as the beast came home "CCI" (see heading) began. Unfortunately I had to discover that some parts were missing completely:
  • Power Controller (DEC # 875-B)
  • Rear Cover for Power Controller and Power Supplies (DEC # 70-20273-00)
  • Rear Backplane Cover (DEC # 70-20271-00)
  • Rear Door (DEC # H9544-B)

So if by chance any of you reading this has got anything of the above left please let me know!

I will have another visit at the magic barn the 750s came from, but I'm not very confident to make a find there.

Some of the missing parts are more or less of a "cosmetic nature" and can be left off without noteworthy consequences, but not having the appropriate Power Controller is harder. It does not only provide simple ON/OFF switching (manual or remote via DEC Power Bus), but has got important other functions as well:

  • line-in filtering
  • automatic disconnect on overtemperature or airflow problems
  • overload and inrush protection
  • display of operational status and fault conditions of the two H7104 PSUs

Nevertheless I will be able to run the 750 without the 875 Power Controller, but the functions mentioned beforehand make it clear I'd rather like to have one.

The rest of the inventory was more pleasant - I have a lot of spare boards now, at least one for every CPU board (except for the RDM = Remote Diagnostics Module) and ample of memory.


There are even two Battery Backup Units (DEC # H7112), but I won't be using these until much later if at all. So I dismantled the BBUs to protect the 750s from acid leaking from the old batteries. At that time the battery packs still looked fine (visually, but certainly not functionally anymore), but one never knows.



Download this file (VAX-11_750_Boards.xls)VAX-11_750_Boards.xls[Table for VAX-11/750 UNIBUS, MEMORY & CPU (CMI) Boards]18 kB