Hi, I’m new here, so I’m not sure if this is the right category. It’s not about a PowerPC, but rather the monitor for one.
I’m having trouble with one of my monitors. I recently bought a beautiful Apple Cinema Display CRT 21", but after what I would say was about 30 minutes of being powered on, I moved it, powered it on again for about 10 minutes, and then it suddenly stopped displaying an image.
I had only used the monitor for about 10 minutes when a friend stopped by. We had a drink in the living room, and when I came back to shut down the PC, there was no image. The power light was still on (green), but the screen remained blank.
After a lot of troubleshooting on both a Windows computer and a G5 Mac (where I could access display settings), I managed to get an image, but only at 800x600 resolution and under 75 Hz—and the image is completely squished horizontally. See the attached picture. https://imgur.com/a/4I7DOqH
My question is: What happened? Is it fixable?
Have a nice day!
TL;DR:
My Apple Cinema Display CRT 21" worked fine for 30 minutes. I moved it, powered it on for 10 more minutes, then walked away. When I came back, no image, but the power light remained on.
After troubleshooting, I can only get an image at 800x600 under 75 Hz, but it is horizontally squished.
What happened, and can it be fixed?
Since you are able to get a picture on the display with all three color primaries, it proves that the CRT tube has not failed, so with enough expertise, the unit can be fixed. Without much troubleshooting data, my guess would be that one or more of the small electrolytic capacitors in the sync processing circuit have dried up or leaked. Low-quality capacitors often do this in under 20 years, so it is ripe for this kind of problem.
The most valuable tool in diagnosing these components is an ESR meter.
Hi, thank you for your answer!
I ordered one, and it should arrive by the end of next week.
I will try to open it up next weekend to see if I can find something. The last time I worked on one was 20 years ago—haha!
From what I’ve gathered, the sync processing circuit should be on the board connected to the back of the tube, right?
Have a nice day!
The board that hangs from the neck of the tube is usually called, fittingly, the "neck board". Its job is to bring the different signals together that feed into the tube's socket connector, and also has protective functions. For example, it may have a spark gap to limit the voltage on the grid electrodes.
The circuits that handle vertical and horizontal sync don't connect to the tube at all, because this type of CRT uses magnetic deflection. The beam is deflected by coils in a yoke that sits around the neck.
Since this is a multisync display, there is a sync processing chip connected to the video input. That board area is usually on the bottom of the chassis near the inputs at the back. I'm guessing the problem is near there.
Note that there are dangerous voltages inside a CRT. Much is made of the anode voltage, which can be around +30,000 V. That is the thick rubber cable that goes to a cap on the top of the tube. As long as you don't remove the cap, it can't hurt you. More dangerous are the power supply capacitors, because they can be charged to nearly 400 V and have high capacitance, so the shock from them can be lethal. I point this out because service often requires testing the display's operation with the cover removed. If you touch your hands or metal tools to the wrong component it could ruin your day.
I commend you if you want to learn to repair them, but there is a lot to learn. I would recommend starting by reading this page, then looking at this guide to see if it describes a problem similar to yours.
Hi, Thanks again for taking the time!
I saw that it’s quite damaged in a few spots, haha. The Mac monitor doesn’t seem to be as easy to disassemble and repair as a CRT TV. I found the repair manual, but no schematics for now…
The links you sent are just incredible as a resource and a great place to start looking. This section seems to describe my problem. I really hope it’s just some old solder—the monitor has no dust inside, so it was barely used…
The seller told me it came from a compulsive buyer...
" Horizontal squashed
A very narrow picture may indicate problems with the power supply to the horizontal deflection circuits, incorrect scan rate selection or defective components, faulty deflection yoke, or bad connections.
If the size is erratic and/or gently whacking the monitor makes the width change, bad connections are likely. See the section: Monitor manufacturing quality and cold solder joints.
Confirm that your video card is running at the proper scan rate - particularly that it is not violating the monitor's specifications. An excessive horizontal scan rate is a common cause of a reduced width raster. Try its software setup adjustments as these may have been lost.
Beyond this, a schematic will probably be needed to isolate the fault."
It sounds like your Apple Cinema Display CRT 21" might have an issue with its horizontal deflection circuitry, potentially caused by bad solder joints or a failing component. Given that you moved the monitor before it stopped working, it's possible that a weak solder joint or a loose connection finally gave out.
Since you mentioned finding a repair manual but not the schematics, you might need to visually inspect the circuit board for any cracked or cold solder joints, especially around the horizontal deflection yoke and power supply. Reflowing suspect solder joints could help.
Also, double-check the video card settings to ensure the monitor is receiving a compatible resolution and refresh rate. If you're lucky, it might just be a connection issue rather than a failing component.