Glitched and extremely slow display/response on vanilla Dreamcast

[DanyLektro]

Hi everyone. Having an issue that I've asked about in a few places and I wanted to know if anyone had any insights.

In short, this is what is happening.

Upon turning it on, the system boot and operating system have rather extremely video glitching and appear to be refreshing at no faster than 3 FPS. This happens with or without a disc in the drive. Inputs are very delayed, however the sound does not appear to be affected and, when equipped with a working GD-ROM drive it appears to boot into a game.

Here's what I've tried to fix it:

-Cleaning all of the electronics with isopropyl alcohol and checking connections.
-Swapped PSU with one from a system that is confirmed to be operating.
-Swapped the GD-ROM drive with one from a system that is confirmed to be operating.
-Tested the PSU in a working unit to confirm that it was operating.
-Tested the GD-ROM in a working unit to confirm that it was operating (it's not, it's dead).

I noticed that one person had a similar issue a couple years ago, but his thread didn't yield any new results for me.

Any ideas? Anyone see a similar issue anywhere?