Chess Champion from Videomaster

The Chess Champion from Videomaster is a chess computer incorporating a 16-key keypad with information displayed on a four digit LED display. There are six levels, four of which are usable for normal chess.

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Manual Download .

Technical Details


Component Location Datasheet
IC 3850PK U1 (datasheet)
IC 3853PC U2
IC AM9217 U3 (datasheet)
IC AM9111B U4 (datasheet)
IC AM9111B U5
IC HBF4001AE U6 (datasheet)
IC U7 Custom daughter board
IC SN75492N U8 (datasheet)

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image alt text Kicad Schematic

Display (ADD 5401) daughter board

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  1. segment F (broken across all digits)
  2. not connected
  3. segment D
  4. segment E
  5. segment DP
  6. digit 1
  7. digit 2
  8. digit 3
  9. digit 4
  10. not connected
  11. segment A
  12. segment G
  13. segment B
  14. segment C
  15. not connected

Display Construction


When powering on random digits or would display random flickering segments or a blank screen, when sliding the S/L switch from S to L the screen sometimes displayed “L” which is the level selection prompt, however this was not always the case, sometimes nothing or garbage.

On opening noticed some rework the traces from corrosion.

First issue broken wires

The main board is connected to the display daughter board by soldered wires, which have broken in a few places, replaced with connectors to allow easy disconnection.

Before After
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Logic Analyzer

Connected Logic analyzer upto the 8 display lines and the input side of the segment driver(SN75492A) to select the 4 segments, by inspecting the output it shows that L is being displayed on the display lines, as digit segments F,D,E are high, when segment 1 is high on the segment driver.

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