Field Service Manual December 2003
Page 201 of 276
Explanation potmeter adjustment
We use light sensitive film for exposure. It means that after developing the areas who were
exposed have become black. The other areas on the film where no light was on the film are
white(blank).
We use a HE-NE(Helium-Neon 632,8nm) laser for exposure.
The most used filmbrands on the SilverWriter are: Agfa, Kodak and Fuji.
How black the image on your film will be depends on the amount of laserlight and the
settings of the developer. For each brand you need a certain darkness(density) on the film.
Which can be measured with a densitometer. Requested intensity are:
Agfa Vivaldi >5
Kodak Accumax ARD7(so-903) >4.5
Fuji HPR-7S >5
During installation the developer, chemistry and deloperparameters are set and should be
kept. For finding the correct density on the film we adjust the laserintensity for exposure. This
is done by parameter 91 of the SilverWriter.
Out of experience we know that for Kodak film we need a laserintensity of about
0,13uA(depending on film and developersettings).
We will use the ‘samp’ command in LTL to reach a laserintensity of 0,13uA. Measurement is
done on the diod with our multimeter connected.
After this the diod will be reconnected to the Maccon . Now the potmeter will be adjusted.
Just like we checked the value before with our multimeter we will do it now with a A/D
converter(rdadc) on the macconboard. The command that shows the value on the screen is
“rdadc .”. By adjusting the potmeter on Maccon we will set a certain ‘rdadc’ value equal to
the 0,13uA. And that ‘rdadc’ value is our parameter91 which we use for exposing.
So when we would set 0,13uA equal to a ‘rdadc’ of 1500, and we would set parameter 91 to
1500 we will have a laser intensity of 0,13uA on the drum for exposing.
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