Back with instabilities. This time the glitching on the screen is more subtle, showing just some small pixelation berore the computer either freezes or boots. Again, it takes some time from a cold boot (5-10 minutes), and after rebooting it freezes almost instantly. I wonder if it’s the overall temperature of the system, the VDP is again failing, some other component like the CPU is failing, or possibly a cracked solder joint on some component?
There may be something causing the VDP to fail: a power supply, capacitor problem or cracked solder.
I once had a PC that shut down after a few minutes due to bad capacitors in the PSU.
