Subject: Re: Fuzzy IIgs monitor
From: [email-masked]
Date: 13 Feb 1997 13:38:20 GMT
Newsgroups: comp.sys.apple2

In article <[email-masked]>, [email-masked] (Laer Haider) writes:

>
>My Apple IIgs monitor is having problems.  When I start the system up,
>the monitor us fuzzy to the point of being unreadable.  It takes about
>20-30 minutes for it to clear up, but it does clear up (I guess from
>warming?).  Can anyone tell me what's going on?  Have they experienced
>this?  How do I fix it?  CAN I fix it?
>
>

     It is hard to say with any certainty. One try is to adjust Focus and base Intensity as described below. Since you will need to open the case, Safety tips and instructions for opening the case are included. ...

from Monitor Repair Mini-Manual  2/97 version
   A2-WUG,1wsw, GS.WorldView

.....

Safety

    Basically: unplug the monitor and let sit for a day, wear goggles,
work on a non-conductive table surface, do not stress CRT neck.

    Unplugging the monitor and letting it sit for a few hours reduces the
danger of shock from stored charges; it does not eliminate it. The usual
warning for this kind of work is AVOID touching two different circuit
points at the same time. Like, don't touch the metal chassis and the
conductive surface of the CRT at the same time.

    WEAR protective GOGGLES. If you should, somehow, bump or stress the
CRT neck-- as in jumping when you get shocked-- it may break. The result may
be a peaceful THOOP! or the CRT may implode in a spray of glass. (Avoid
using the CRT's neck to support the monitor in any position.)

    Work on a wooden or plastic-topped table with plenty of space. Try to
position yourself, tools, and the monitor so that when you get 'stung',
the chances of breaking something are reduced.

    As much as posible, avoid using heavy tools of any kind. An inadvertant tap from a mini-screwdriver is much less likely to crack the CRT than a bonk from a full-sized screwdriver or pair of pliers.

    Rubber gloves are probably a good idea so long as they do not get in
the way. Of course, pointy connections and components can puncture gloves.

    It's a good idea to clip a wire to the chassis and touch the other end
to the conductive surface of the CRT a few times before doing any work in
order to drain off any charge there.

Note: Several places in a monitor or TV carry high enough voltages to
deliver an uncomfortable shock. Draining the charge from one point does
not guarantee that other points have been discharged.

Joe Walters contributed some info on Discharging the HV anode ... 

The HV charge (20,000+ volts) might not be much reduced by just waiting a
few hours (or days), especially if you are in a low humidity location and
the tube, etc., are all of good quality.

1. There is a long wire (called the anode) that goes from the high
   voltage power supply to the top of the tube where it is snapped
   into a hole. You can't see the hole because there is a rubber
   shield built onto the wire. The end of the wire goes to a metal
   clip which, without the rubber shield, looks somewhat as below.
   One squeezes the clip so the end slips into the hole in the tube.
   
   ---     ---
==  \   /  ===== back of CRT
       \ /  <-- metal clip (This is what your grounded
        |                                      screwdriver needs to touch.)
       [|]  insulated Anode lead going to HV module 
       [|]

   Needless to say, UNPLUG the monitor before beginning. Simply
   turning it off isn't good enough.

2. Get a clip lead and clip one end to a long slender screwdriver

3. Clip the other end to the metal chassis of the TV  (i.e the metal frame
parts)

4. Carefully! slip the screwdriver tip under the rubber flap on the
   top of the tube until it touches the internal wire that both
   holds the anode wire in place and conducts electricity.

Step 4 may result in a somewhat loud "SNAP" as the tube is
discharged. Be prepared so you don't jump and break something.

============

Opening the Case ...

    Whatever it is you plan to fix, if you remove the monitor case, you
will probably need to unplug the cable running from the circuit board to
the Controls/Switch Module on the side of the case. Use 'whiteout',  nail
polish, etc. to mark the position of the plug. In more detail ...

  1. Unplug everything from the monitor & let it sit for a day.
 
  2. Put on protective GOGGLES. Place the unit face down on a wooden or
plastic-topped surface with lots of space and good lighting. Remove the
the screws. Place the unit in nomal position.
 
  3. Have a fat magazine ready. Slide the case off until you are able to
see the control leads plugged into the main board on the right side of the
case. Mark the plug position with 'white-out', nail polish, etc.. Unplug
the connector.
 
  4. Slide off the case while supporting the monitor and slide the fat
magazine under the circuit board to prop up the monitor from behind.

  5. Discharge the HV (optional, but, generally, a good idea).
 
  6. <Do adjustments, fixes on Monitor>
 
  7. When done, reinstall the control assembly.
 
  8. Still wearing GOGGLES, support the monitor, remove the magazine,
slide on the case, reconnect the plug, finish sliding on the case, replace screws.

.....

============

 Adjusting Focus and Intensity on a blurry GS RGB Monitor.

    These adjustments may also help cure display "bowing", etc.. 

    Intensity and Focus controls are on the High Votage
Module (black module near back of circuit board) inside the case.
 
   Follow procedure outlined earlier for safety (e.g. unplug, wait,
wear goggles, ...) and removing the case.
 
    Note the position of the two controls on the HV Module (at the left,
back).  Mark the back of the cover where handy access hole should be.
 
    Take the case cover to another area (i.e. away from the exposed CRT
neck).
 
    Remove the control assembly from the right side of the case.
 
    Using a Dremel tool, hole saw, ... cut an approx. 1" diameter hole in
the back of the case. Use this opportunity to give the case interior a
good cleaning. (If you wash it, be very sure it's dry before continuing.)
 
    Reinstall the control assembly.
 
    Put everything back.
 
    Reconnect cable and AC cord. Turn on the computer & monitor.

    Use the normal side of case controls to get the
brightest, 'decent-focus' picture you can obtain.
 
    Using a plastic TV technician's tool (and flashlight if necessary)
adjust the Intensity and Focus controls (through the hole in back) on the
HV module to get a good looking display.
 
    Work back and forth between the back and side controls. What you're
aiming for is a display with good brightness and sharp focus when the side
controls are near their middle positions.
 
    Cover the back hole using a piece of duct tape, a large sticker,
etc.. (The opening is a potential shock hazard, especially if the monitor
is within reach of children.)

Rubywand