My Amiga A1200 is no longer able to display any picture on the screen from either the RGB or Composite ports, although my TV stopped saying “No Signal” and I tested it on 2 other TVs at a meeting. The Power light and Caps Lock light, as well as the light on a USB mouse with TruMouse adapter all come on, but it doesn’t boot up from CF cards or a Gotek drive. The Gotek LCD display lights up.
It was still working on January 29 or 30, but not on January 31. It was recapped and repaired after being rained on through a skylight, but the repairs took several months. The board was covered with gunk, corroded, ignoring internal and external floppy drives after the repairer broke a track, the IDE port has been repaired and the RGB port has been replaced. The Gotek drive is only about 6 months old, but the CF card cable is much older. After using it for about an hour following the repair, the whole screen turned blank and bright green, but I couldn’t get rid of it by turning it off, waiting and rebooting, so indicating a Chip RAM problem. I had to send it away for repair again under warranty.
The U16 RAM chip and one next to it had failed and the pins on the Kickstart ROMs had rusted, there was a problem with the display sync, and the 74HCT244 buffer chip was replaced with one from an A600. The repairer said “The reason the A1200 with your Alice chip was failing before was because the video buffer chip also buffers the CCK logic line from Alice. The CCK logic line is the main clock line from the Alice chip to all the other chips on the board. The faulty buffer chip was affecting this CCK line meaning all the Amiga's custom chips (which rely in all being exactly in sync) were all talking at different times, effectively. So by fixing the video sync line, it also fixed the CCK line, and made everything nice again”.
Since receiving it back 11 months ago, I’ve had some problems with my 8Mb RAM expansion just because I removed it to fit an FPU, then plugged it back in. I had to clean the expansion port contact pins and my Amiga wouldn’t boot up with the FPU in place until I jumpered it to off. My Early Startup screen started losing sync whenever I selected it, but stabilised when I pressed the space bar to select NTSC, then PAL. The numeric pad and one cursor key stopped working. I've tried removing my 8Mb RAM expansion card, but this makes no difference to my current problem.
I’m afraid my flat is suffering from damp and mould I now know is caused by leaky pipes in the walls. I’m moving out in the near future. The default level of damp is about 82%, so I think this is what has caused my latest Amiga problem.
How might I be able to fix this problem before sending it away to a repairer? I had a differerent repairer recommended to me earlier this week as being quick and reliable, but I can't be sure. I think my A1200 might just need a good clean and a simple repair which I might be able to learn how to do.
