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DEC PDP-11/05 GT40 Graphics Terminal

This DEC GT-40, S/N 185. was donated by John Wilson on 1/27/19.

The Digital Equipment GT40 Graphics Terminal was introduced in 1972 at a price of about $11,000. It consists of the VR17 Display Assembly that can have an attached LK40 keyboard and 375 light pen, and the VT40 Computer. The VT40 computer is a PDP-11/05 that contains the VT11 Display Processor, and a DL11 Asynchronous Line Interface. The VT40 can have either 4k (GT40-AA) or 8k (GT40-BA) of core.

PDP-11/05 GT40 Restoration



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The left side of the PDP-11/05 processor with the covers removed.
The top board that is visible is the A320 Light Board.

 Slot P/N Description
 1 A320 Light Board 
 2 M7013  VT11 Display Control & Character Generator    
 3 M7014  VT11 Bus Control & Bootstraps 
 4 M7800  DL11-E Asynchronous Line Interface
 5 H214 MM11-K Core Memory Stack 8K x 16
 6 G231 MM11-K Core Memory Drivers
 7 G109     MM11-K Core Memory Control
 8 M7261  KD11-B Processor Data Path
 9 M7260  KD11-B Processor Control

To Do:
  • Check the operation of the console lock switch
  • Check the DCOK signal from the power supply
  • Replace the broken resistor on the M7014 Bus Control & Bootstrap board
  • Find a DL11-W serial console board and two cables
  • Buy spare AC KBPC25-02-5 diode bridges for the power supply
  • Find a G840 FlipChip to go with the 375 Light Pen that Mattis could donate.
  • Make sure that there is an M930 Unibus terminator in slot AB05.
Done:
  • Replace the AC diode bridge (D14) in the power supply with one borrowed from a spare broken power supply


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The GT40 consists of the VR17 Display Assembly and the PDP-11/05 that contains the VT11 Display Processor.

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This PDP-11/05 was assembled in San German Puerto Rico.

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This VR14L monitor was assembled in Westminister, MA.


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The A320 Light Board Component Side.

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The A320 Light Board Solder Side.

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The M7013 VT11 Display Control & Character Generator Component Side.

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The M7013 VT11 Display Control & Character Generator Solder Side.

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The VT11 Bus Control & Bootstraps Component Side.

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The VT11 Bus Control & Bootstraps Solder Side.
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