21 May
2012
21 May
'12
2:43 p.m.
On Mon, May 21, 2012 at 5:20 PM, Jim McCusker <jim_mccusker at hotmail.com> 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?
Bad solder joints or cracked/lifted traces should be easy to visually
identify and easy to correct. If you are careful not poke around live
circuits with conductors (i.e., screwdrivers), you could remove the
back of your monitor, power up the PET, and tap at the body of the
brightness control with something non-conductive, like a chopstick.
The idea is to see if the problem follows the entire pot or just the
handle of the pot - it's possible you have bad/broken traces, in which
case moving the body would also produce symptoms, or it's possible the
pot itself is mechanically defective, in which case, the body is
stable but agitating the knob causes symptoms.
I've done some minor work on those boards (defective 7812 regulator),
and they aren't that hard to work on, but if you haven't worked around
CRTs, do look up and follow safe handling procedures.
-ethan