[comp.sys.amiga.hardware] coarse video adjustment

clindsey@nmsu.edu (Coy Lindsey) (12/14/90)

I just got my A3000 and has worked great (except improperly
seated expansion bus card causing yellow screen and no boot) but I do
have flicker in interlaced productivity mode.  I have tweeked the fine
adjustment pot all the way to the end of the pot but cannot get rid of
the flicker.  The books says that there is a coarse video adjustment
but that it should be made by an authorized service center.  In
looking at the schematics (magnifying glass in hand) I found a
variable cap VC470 that is part of the same circuit as the fine
adjustment pot (VR470).  Is this the coarse adjustment?  Can I just
tweek it or does the coarse adjustment require specialized test
equipment?  If its just visual, I can tweek just as well as the next
guy.


Thanks for any useful info

Coy Lindsey

hood@cbmvax.commodore.com (Scott Hood) (12/15/90)

In article <CLINDSEY.90Dec13094746@tecate.nmsu.edu> clindsey@nmsu.edu (Coy Lindsey) writes:
>I just got my A3000 and has worked great (except improperly
>seated expansion bus card causing yellow screen and no boot) but I do
>have flicker in interlaced productivity mode.  I have tweeked the fine
>adjustment pot all the way to the end of the pot but cannot get rid of
>the flicker.  The books says that there is a coarse video adjustment
>but that it should be made by an authorized service center.  In
>looking at the schematics (magnifying glass in hand) I found a
>variable cap VC470 that is part of the same circuit as the fine
>adjustment pot (VR470).  Is this the coarse adjustment?  Can I just
>tweek it or does the coarse adjustment require specialized test
>equipment?  If its just visual, I can tweek just as well as the next
>guy.
>
>
>Thanks for any useful info
>
>Coy Lindsey

The A3000 display enhancer does not display enhance the
interlaced-productivity display modes, only the interlaced or
non-interlaced display modes.  The ECS display modes, such as SuperHires
and Productivity (interlaced or not) are special display modes that the
display enhancer does not improve.  Thus the fine or coarse tuning
adjustments do not affect these display modes, i.e, don't mess with
them.

Regards,
Scott Hood

-- 
--
Scott Hood, Hardware Design Engineer (A3000 Crew),  Commodore-Amiga, Inc.
   {uunet|pyramid|rutgers}!cbmvax!hood   hood@cbmvax.cbm.commodore.com
  "The views expressed here are not necessarily those of my employer!"