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Amiga Technical References
Video Banding Modification
Video Banding Modification: Many (most?) A4000s show some faint vertical
bands on the display. There is a modification to prevent this, but, like
anything else, it has advantages and disadvantages.
- Removes vertical bands from display.
- Simple modification.
- Relatively easy to disable.
The modification involves connecting pin 15 of the video port connector through
a 100 ohm, 1/4 watt resistor to ground. This can be done inside the A4000, but
it's safer and more versatile if the modification is performed on the
DB23-to-HDD15 adapter that was included with the A4000. That way the adapter can
be unplugged from the machine if a genlock or Amber board is to be used.
- Interferes with operation of attached genlocks and deinterlacer boards
like the Amber A2320 board (see Boards/A2320 'Amber'
There are two grounds on the adapter PC board: shield ground and video ground
(pins 16-20). Since all the other components on the board use the video ground,
it seems reasonable to use it for this modification, rather than the
more-easily-reached shield ground. The resistor fits nicely on the bottom of the
adapter PC board, running from pin 15 to pin 18 of the connector's soldered
Copyright © 2000 Amiga Auckland Inc. All rights reserved.
Revised: June 17, 2005.