Re: Seeing red

[Rubywand <rubywand@swbell.net>]

"mystix"@direct.ca@direct.ca writes ...
 ....
> icssofty@aol.com (ICS Softy) writes:
> 
> > described how to fix it but I can't locate it right now.
> > But in a nutshell, you replace the 22 microhenry peaking coil in each
> > circuit (there's only one for each gun on the board and they aren't
> > hard to find.).
 ....
> 
> Thanks. This is helpful, and it doesn't sound as bad as
> I might have feared.
 ....

     The fix for an all-blue, all-red, ... screen was published in Computist
back in 1987 or so. Usually, the problem is an 'open' to the input to one of
the transistors which controls a color gun. The transistor is ON all the time
and so is the color gun the transistor is supposed to control.

     The component which usually seems to be responsible is the little choke
mentioned by ICS Softly.

     You have three gun control circuits on the small card attached to the
back of the CRT. Each circuit has a transistor which is easy to spot
(usually, the output transistors will be a bit larger than average) and, near
each transistor will be a choke. The choke will probably look like a blob
with spots for color coding the value. (Or, it may look like a coil-- depends
upon whether or not it's been dipped in epoxy.)

     If the three circuits are labeled "Red", "Green", "Blue", picking the
choke to pull and replace is easier. After pulling a suspect choke, check it
with an Ohm meter to see if it's open-- i.e. very high R. (If it's not open,
the choke is probably okay.)  There's more about this, including information
about opening the monitor case, in the newsgroup FAQs at
http://home.swbell.net/rubywand/Csa2MONITOR.html#008 .

     Replacing all three chokes is likely to fix the problem; but, it's more
work. Besides, it's nice to be sure that you have caught the bad component.




Rubywand