bryce@COGSCI.BERKELEY.EDU.UUCP (08/31/87)
A while back I mentioned that my 1080 monitor has had it's picture tube
shrunken so that more pixels would fit on the screen. Several people wrote
to ask how to do this. Enough interest was expressed to post the answer
to the net:
The purpose of mucking with any of this is to add more active, useable
pixels to your Amiga's display. They display I'm typing on right now is
704 pixels horizonal and 232 vertical, a heathy bonus over the 640*200
that most of you are probably looking at.
The transformation involves two stages. The first is entirely software and
requires no modification to your hardware. Several programs are available
to do the work, the two most common are called "ScnSizer" and "MoreRows"
and usually come bundled with documentation and or source code in a file
with a name like "SCNSIZER.ARC" or "MOREROWS.ARC". These are available
from your local software source, a Fish disk, or almost any BBS system.
MoreRows allows you to specify how many additional pixels you wish your
Amiga to generate when displaying the Workbench screen. The procedure is
to invoke it from the CLI with a command like "MoreRows -rows XX -columns
YY" where XX and YY are the number of extra pixels to add. How many *you*
can actually add depends on your monitor; the maximum is 32 and 64, but
start with safe numbers like 8 and 16. After MoreRows, start up
preferences. Set the screen centering gadget to the very top left corner,
select "save", wait for disk access to finish then hit the 'Ol Vulcan Nerve
Pinch (Ctrl-Commodore-Amiga). The changes do not take effect until you
reboot. You do *not* need to add anything to your Startup-Sequence, the
information is stored in the preferences structure. You will probably need
to adjust the screen centering gadget again.
CAUTION: A very few brain-dead programs will not work with MoreRows. A
larger section of programs fail to take advantage of the extra space...
this causes no harm but user frustration. (These programs should use
GetScreenData() or read GfxBase->NormalDisplayColumns and
GfxBase->NormalDisplayRows to find out the size and also set any window
"maximum" limits to -1,-1 or 0xFFFF,0xFFFF)
At a certain point, adding more pixels uses up DMA time slots that would
otherwise be used for hardware sprites. The high numbered sprites will go
first. (The pointer is hardware sprite #0).
It is important to realize that MoreRows does not shrink the size of
pixels... it just adds more of them. It should be clear that you will soon
run out of visible space on your picture tube! The extra pixels will still
be generated by your Amiga, still be displayed by your monitor... but you
won't be able to see them. The reason for this extra "overscan" is related
to the design of television pictures which must fill the entire picture
tube from edge to edge.
The solution to be able to see more and more extra pixels is to shrink your
display. Smaller pixels on the same picture tube equals more pixels.
A friend of mine who did the modification for my monitor, Bruce Takahashi.
Bruce is a *fantastic* repair person, very talented. His number one tip on
making the modification was this: "If you know enough about TV servicing
to be making this modification, you already know what to do and don't need
me to tell you. There are very hazardous voltages inside, you should be
wearing safety glasses and you should have another person in the room to
perform CPR in case you blow it.". If you happen to break your picture
tube you and/or your eyes may be shredded as it implodes. If you leave it
plugged in or neglect to discharge the proper high voltage components to
ground (preferably with a resistor) you may receive... er... the shock of
your life.
That said, the horizontal and vertical size controls must be twiddled, then
a convergence must be performed. Again, simple if you already know how.
The horizonal inductor is inside the case, the vertical control is a
potentiometer, accessible from outside. If you twiddle the vertical control
be sure to use a *non-metallic* screwdriver. Using metal will most likely
cause an arc and blow out your monitor's high voltage transformer. (The
special little plastic screwdrivers with tiny metal tips are designed for
this adjustment).
Since you are controlling *both* the horizontal and vertical size, a factor
you may wish to consider is the aspect ratio of the display. You can
either ignore it, set it such that pixels come out exactly square, measure
what you have now and duplicate it, or find the "ideal" values and
duplicate them (see the pervious posting, search for "aspect" in the
Keywords:). I don't know any "typical" values for active/total
display area on a 1080 since I don't have a "typical" monitor.
If you have ever hear a sharp "pop" from your monitor, followed by a jump
on the screen and wondered what caused it, Bruce suggests that you re-route
high voltage lead to the picture tube so it is as far away from metal as
possible. Seems that dust enters the monitor and builds up to the point
where it arcs. This spike can also affect other things, like flaky hard
disk drives.
Any TV repair shop should be able to make this modification for you. If
you live in the area of Berkeley, California Bruce Takahashi even does
house calls. A flat fee of $45 will get the adjustment including final
check out with an Amiga, the MoreRows program (you supply the blank disk)
and a warranty on the modification. The phone number is 415-525-6973, and
the address for mail is Bruce Takahashi, 1442 A. Walnut Street #420,
Berkeley, Ca 94709-1496.
|\ /| . Ack! (NAK, EOT, SOH)
{O o} .
( " ) bryce@hoser.berkeley.EDU -or- ucbvax!hoser!bryce
U If "hoser" does not work, try my old address at "cogsci"
Excpect my mail to be flaky as the bugs get worked out at hoser.