How to make your own Amiga db23 to vga adapter - jbilander/HowTos GitHub Wiki

How to make your own Amiga db23 to vga-adapter

 DB23 female socket (towards Amiga side)

  3  RED     -->   Analog Red (75 Ohm)
  4  GREEN   -->   Analog Green (75 Ohm)
  5  BLUE    -->   Analog Blue (75 Ohm)
 11  /HSYNC  -->   Horizontal Sync (47 Ohm)
 12  /VSYNC  -->   Vertical Sync (47 Ohm)
 16  GND     ---   Video Ground for RED Analog
 17  GND     ---   Video Ground for GREEN Analog
 18  GND     ---   Video Ground for BLUE Analog
 19  GND     ---   Video Ground for CHV SYNC
 20  GND     ---   Video Ground
 23  +5V     -->   +5 Volts DC (100 mA max)

 DE15 female socket (HDD15).

  1  RED video
  2  GREEN video
  3  BLUE video
  5  GND Ground (HSync)
  6  GND RED_RTN Red return
  7  GND GREEN_RTN Green return
  8  GND BLUE_RTN  Blue return
 10  GND Ground (VSync)
 13  HSync Horizontal sync
 14  VSync Vertical sync

Connection diagram:

A Hex Schmitt Trigger Inverter (74HCT) is used for buffering the HV-Sync signals and a .01 uF ceramic decoupling cap between +5V and ground near the chip power supply pin.

  DB23                                VGA HDD15

  Red    (Pin 3)  ------------------- Red        (Pin 1)
  Green  (Pin 4)  ------------------- Green      (Pin 2)
  Blue   (Pin 5)  ------------------- Blue       (Pin 3)
  GND R  (Pin 16) ------------------- GND Red    (Pin 6)
  GND G  (Pin 17) ------------------- GND Green  (Pin 7)
  GND B  (Pin 18) ------------------- GND Blue   (Pin 8)
  GND HV (Pin 19) ------------------- GND HVSync (Pin 5,10)
  GND    (Pin 20) ------------------- GND for inverter chip and 
                                      .01 uF decoupling cap
                      |\     |\
  HSync  (Pin 11) ----| >o---| >o---- HSync (Pin 13)
                      |/     |/

                      |\     |\
  VSync  (Pin 12) ----| >o---| >o---- VSync (Pin 14)
                      |/     |/

  +5V    (Pin 23) ------------------- Power supply for
                                      inverter or buffer chip.

Since db23 d-sub female connectors are very rare, I will use a cheap d-sub db25 and cut it down to a 23 with a hacksaw.

Cut out a piece from a prototype board and solder on a decoupling capacitor .01 uF = 10nF
I'm using a 16VDC 0402 here which is very small...You sneeze and it's gone forever!...You can use a 0603 or 0805 just as well if you find it easier to solder.

A Hex Schmitt Trigger Inverter (74HCT) is used for buffering the HVSync signals. I used a M74HCT14B1R connected as follows. Unused inputs are not left floating but rather connected to the +5V here.

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