Author: Anthony Green (250.66.233.220.exetel.com.au)
Date: 06-02-2008 15:11
Given this is a mono monitor, the problem is almost certainly with the monitor or the cable and not the computer, other than broken socket contacts on the circuit board.
The vertical lines are periodic, this may be caused by a cyclic source of noise, picked up through the cable as previously suggested.
Try the following if you can:
* Test this monitor with an other Atari ST of any type located at the same place as yours, to ensure no variations exist in RF noise in your environment. If the monitor picture is fine, it suggests a fault lies in the computer as the cable and monitor were ok for this second computer. The first fault to check for is that the socket pins soldered to the ST's motherboard are not cracked. If cracked, you will need to re-solder.
* Try the computer with monitor in another location, say 20 miles away. If the picture is now fine, you probably have a strong RF source, of low frequency, causing noise to be picked up in the cabling. Try wrapping the monitor cable in aluminium foil to shield the cable further. Make sure you don't touch anything electrically live.
* Change the cable if you can. If you can't, don't worry.
* If you have still not been able to get a good picture from the display in these different configurations, the fault lies in the monitor. I have seen a similar problem with a TV many years ago and the resolution turned out to be a number of capacitors had to be replaced due to their age. Given this monitor is a similar age to my TV at the time, this is the next thing you can try. Make sure you replace all components with the correct type of capacitor. This is especially important if it is electrolytic (look like tin cans/cylinders) and make absolutely sure you replace them with the negative terminal on the correct side (the - terminal). That is, they have the correct polarity.
Given what you see on the screen, the transistors and the PSU components appear ok, otherwise the image would collapse vertically or horizontally or give nothing other than a high pitched hum.
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