Path: news1.icaen!news.uiowa.edu!NewsNG.Chicago.Qual.Net!nyd.news.ans.net!newsfeeds.ans.net!news.idt.net!netnews.com!newsswitch.lcs.mit.edu!nntprelay.mathworks.com!cyclone.swbell.net!typhoon01.swbell.net.POSTED!not-for-mail Message-ID: <360A445A.AFE99F72@swbell.net> From: Rubywand Reply-To: rubywand@swbell.net X-Mailer: Mozilla 4.06 [en] (Win95; I) MIME-Version: 1.0 Newsgroups: comp.sys.apple2 Subject: Re: How may I fix my Apple IIGS monitor? References: <19980924071924.00797.00001310@ng85.aol.com> Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Lines: 169 Date: Thu, 24 Sep 1998 08:08:42 -0500 NNTP-Posting-Host: 207.193.11.173 X-Complaints-To: abuse@swbell.net X-Trace: typhoon01.swbell.net 906642514 207.193.11.173 (Thu, 24 Sep 1998 08:08:34 CDT) NNTP-Posting-Date: Thu, 24 Sep 1998 08:08:34 CDT Organization: SBC Internet Services Xref: news1.icaen comp.sys.apple2:139675 Supertimer writes ... > > The symptom is no image except a single horizontal line > at the center of the CRT. > > How may I fix this? Has anyone had this problem? .... Several years ago, our monitor display would flick into a single line from time to time. It turned out that the High-Voltage Flyback transformer had one or more loose pins. Note: The HV Flyback transformer is the black thing near the back left side of the main circuit board. It has the Focus and Intensity controls mounted in it and a fat lead running to the anode of the CRT (picture tube). Unfortunately, the holes into which the HV Flyback transformer mounts on the board are too large for the pins. So, each pin is surrounded by more solder than is usually rquired for connecting something to a board. Sometimes, this solder fractures-- i.e. develops cracks-- and the connection between the pin and the circuit board is disrupted. The cure was to resolder all of the HV Flyback transformer pin connections using good quality solder (something like Kester "44" rosin core 63-tin alloy solder). Naturally, there is a high-voltage shock hazard to consider even with the monitor OFF and unplugged and allowed to sit for a day before beginning work. Another hazard is the picture tube-- Do Not Break it. Here is some info on safety and setting up to work on the monitor ... >> 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. =========================== From: Joe Walters 004- How do I discharge the High Voltage? 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. =========================== From: Rubywand 005- How do I open my RGB monitor's case and get set for doing internal adjustments or repairs? 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. 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. = = = = = = = = = = = = = = 006- What tools and solder should I use for repairs? For any soldering use a good quality pencil-style iron rated at 25-40 watts with a holder and sponge. Use high quality (60/40 tin/lead or better) rosin core solder (e.g. Kester "44" 20 gauge). << There are other possible causes for a flat lined display. However, a loose HV Flyback transformer connection is a well-known source of trouble for this monitor. Rubywand