Commodore Pet 2001-8 w/flaky brightness adjustment - test-drb@ccmp.vtda.org

21 May 2012

I have a 2001 that was doing the same thing and blasted it a few times with contact
cleaner and it works fine now.

Win

Subject: RE: Commodore Pet 2001-8 w/flaky brightness adjustment
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...
  On May 21, 2012, at 5:20 PM, Jim McCusker wrote:

 I have a working Pet 2001-8 that has one annoying issue.   When I power up the unit I
typically don't see any characters displayed unless I apply a slight amount of
pressure on the back of the brightness control in the back of the monitor.   I suspected
bad solder joints but couldn't see anything wrong.  Turning the control brightens the
screen but somehow this control is causing the character display to turn on/off.   Any
ideas what might be going on here?  
 Could easily be dirty contacts on the wipe for the pot.  Try isopropyl
 alcohol, or any number of commercially-available contact cleaners for
 stereos, etc.

 Or, given your description, the slight flex you're applying might be
 wiggling other bad solder joints elsewhere on the board to the point
 where they connect.  I've had that happen (it was a nasty bugger to
 find, too). 
Thanks Dave, I'll give the isopropyl idea a try, followed by closer inspection of the
circuit board while the back is off.  I have the circuit schematics but not enough
experience with monitors to feel confident touching very much inside while the circuit is
energized.   I'll take some photo's if it's still not working and see if
anyone familiar with the circuit sees anything.    Once I get this working I'll be
working on a few bad chicklet keys and then I'll have a complete working system.
--Jim                         