Prof. Dr. rer. nat. Peer Johannsen

Weird Science - Tales from the Vectrex Academy Lab

Vectrex Project Title

  • SCOPETREX Experiments


  • Experiments with a SCOPETREX board (for information about SCOPETREX, see here)
  • The board used here was assembled by one of my students as a tutored project work.

Project Status

  • Ongoing
  • Assembly of the board is completed, first tests were successful (see pictures below).
  • Interrupt-line on the board fixed (design-bug)
  • 3D printer files of the case uploaded

Picture Gallery

The SCOPETREX board on my oscilloscope

  • The oscilloscope is a HAMEG 204 in YX mode, using the additional Z-input to control the blanking of the electron beam.
  • The quality of the pictures is sometimes a bit poor, but just because of the camera used to take the picutres. On the oscilloscope, the display is amazingly great.

Using the Test Rev4 cartridge to calibrate the board

  • It is sort of eerie how perfect the Test Rev4 cartridge works for calibrating the output of the SCOPETREX board on the oscilloscope. Note the alignment of the vectors to the raster lines on the oscilloscope screen.

  • The "Focus" test of the Test Rev4 cartridge is good and useful for calibrating the "Focus" setting of the oscilloscope. I do not know of any focus adjustment in the Vectrex hardware, so maybe this test was originally programmed and used with an oscilloscope and/or the tube protypes while the actual Vectrex hardware was still being developed?
  • My speculation is that the Test Rev4 cartridge was there first. Before the Vectrex BIOS was completed. This speculation is derived from the fact that the Test Rev4 code contains and uses several copies of BIOS routines (see here), so some tests actually run without using the BIOS.

The SCOPETREX board connected to a Vectrex CRT

  • As a second experiment, I disconnected the logic board of my Vectrex console from its analog board, and then connected the SOPETREX board to it. Many thanks to Brett (playvectrex) for his long-distance support and helping me getting properly grounded signals here.
  • I have not found any information on the internet about someone having tried this before, so I am posting some pictures here.

  • Note that the display is not perfectly centered. That would involve realigning the coils of the Vectrex CRT, and I did not do that in order to be able to easily return the console to its original state.
  • Other than that, I could not see any noticeable difference. The "new" hardware of the board does not seem to improve the image quality. Also the infamous mystery gaps and the slanted texts are still there, but we already knew that those are inherent to the DACs and not a result of aging. I have not yet tested how vector drift is with the new board.

A Vectrex console connected to an oscilloscope

  • For the sake of completeness, here are also some picture of a regular Vectrex console connected to an oscilloscope (a digital one as well as an analog one). Note that the intensity signal of the Vectrex console is not correctly handled by the oscilloscopes due to internal reasons, so all lines are visible. Still an interesting and valuable method to debug a Vectrex console.

Interrupt line on the board

  • The ScopeTrex board layout is known to have a minor flaw. The interrupt line is not connected, so cartridges and games that use interrupts (e.g. Bedlam) do not work properly. We have fixed this on my ScopeTrex by adding an additional wire, and now interrupts work.
  • The picture below shows the pins which need to be connected (green circles).


3D Printer files of the case

  • The ScopeTrex case shown in the pictures above was designed and printed by one of my students who kindly agreed to share the necessary files here for non-commercial use.
  • Download:


Latest modification on 06/04/2024, 16:30
  • Section about fixing the interrupt line on the board added
  • 3D printer files of the ScopeTrex case uploaded