Graphical Glitches on Amiga 500

kgllewellyn

The RetroHoosk
Joined
Jan 15, 2021
Posts
5
Country
United States & Canada
Region
Blaine, WA & Vancouver, BC
Hi there,

My A500 has sadly sprung up an annoying glitchy graphic issue. Initially, it would start off with booting up as normal and then about after 6 minutes of use, the screen would glitch up and the machine would crash with a grey screen. Upon rebooting I was presented with a light-green screen which indicated problems with the CIAs.

After powering off for 10-15 minutes, it the issue would clear up, but once again after 5-6 minutes use the problem would re-occur.

This afternoon I've been swapping in the chips from my CDTV to narrow down the fault. I'm not sure when the situation of the issue changed, probably when I swapped one of the CIAs the issue changed to immediate graphics glitches upon boot, but the machine now never fails to post, so an improvement there? However, the more you interact with the A500 the worse the glitches become, icons become scrambled when double-clicking, as do windows when they open and so forth. After awhile the machine crashes out with a screen that's blue in Workbench 1.3 or gray in Workbench 3.x.

The only one I haven't been able to rule out is Fat Agnus, mostly because I can't see the equivilent chip in my CDTV, I think it's on U44 on my CDTV but it has CSG 8372A not the MOS 8372A. I'm also not sure with the orientation to install it in my A500 as the MOS has the text rotated 90 degrees when facing from the front, and the CDTV doesn't. The CDTV has a silver splodge on the 8372A in the top left, while the A500 has a dimple on the right side of the 8372A, I imagine this is to help with orientation, but I wanted to be sure before I go swapping it over willy-nilly.

Any and all help is really appreciated. Really gutted that this happened just after the video decided to pack up on my CDTV earlier this week. Dx - Not a great start to 2021!
 
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