Drew wrote:
> On 14 Oct, 23:26, "Michael J. Mahon"  wrote:
>> Drew wrote:
>>> On Oct 14, 10:06 pm, Alex Freed  wrote:
>>>> Drew wrote:
>>>>> Well i connected the GS via the composite in and it
only came up in
>>>>> BW, so connected my xbox 360 and to be honest at first
glance it look
>>>>> ok, but then again it seemed a distinct lack of red in
any of the
>>>>> images
>>>> If it is "black and WHITE" then red channel must
be operational or it
>>>> would be black and blue-green.
>>>> There are generally  two separate controls for each color:
black level
>>>> and gain. Just like brightness and contrast per color. Chances are
>>>> adjusting these controls should do the trick.
>>>> And get color bars on the screen before attempting to
adjust. If there
>>>> is no other source, I guess "color test" from
DOS 3.3 master should do.
>>>> -Alex.
>>> Cheers for the advice guys, was just using the control panel program
>>> to check the colours and had another GS on with my Apple RGB monitor.
>>> Only found one set of controls, labelled bias...would that be gain?
>> "Bias" is equivalent to "brightness",
"gain" would be equivalent to
>> "contrast".
>>
>>  From your description, it sounds like the red channel gain needs to be
>> turned up, or if it's up and insufficient, then a component in the red
>> channel video amplifier is the likely cause.  Often the high-level part
>> of the video amplifiers is on a PC board at the CRT socket (back of the
>> neck).
>>
>> Low gain is often caused by imperfect contacts, loose connections,
>> or open bypass capacitors in the (red, in this case) video amplifier
>> circuit.
>>
>> -michael
>>
>> AppleCrate II: An Apple II "blade server"!
>> Home page:  http://members.aol.com/MJMahon/
>>
>> "The wastebasket is our most important design
>> tool--and it's seriously underused."
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>> - Show quoted text -
> 
> Hi,
> 
> If I turned the brightness down the red would pretty much disappear to
> a dark blue/black. I will take the back off again tonight and have a
> look for gain adjustment. Though its nice to have some red :-). Its
> quite usable the way it is, but if i can make it better that would be
> good.

Although the maintenance manual no doubt has very specific instructions
on how to adjust the color bias controls, a baseline adjustment can be
made very similarly to the way you should adjust monochrome brightness.

Display a black raster from the computer and slowly advance the bias
control until the color it controls just becomes visible, then back
it off slightly.

This procedure sets the bias as high as possible without interfering
with the color purity of lowlight areas.

Similarly, when a white raster is displayed, the red gain control
should be adjusted to produce a white (not red and not cyan) screen.

This procedure sets the red gain to produce the same effect as the
green and blue channels, causing a pure white.

-michael

AppleCrate II: An Apple II "blade server"!
Home page:  http://members.aol.com/MJMahon/

"The wastebasket is our most important design
tool--and it's seriously underused."
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