Twitchy SE/30 Screen

[JAG]

I haven't seen this discussed before, nor mentioned in my Dead Mac Scrolls book

I have an SE/30 that was working just fine stock, but after installing a DayStar socketed 50Mhz upgrade and a MacCon PDS slot ethernet card, the screen is "twitchy"

The best I can describe it is that the screen moves down just a few pixels every few seconds and appears to be related to opening / closing windows. If I don't do anything, it's far less noticeable.

I checked the PSU voltage via the floppy port and it's a solid 4.93V even when I open and close windows, etc it doesn't waver even a hundredth of a volt.

I'd really like to keep these mods installed.

Any ideas?

[uniserver]

my guess is there is some RF interference, i would get some tinfoil and ground it, then take 2 pieces of (paper or plastic) one on top and one on bottom,
so the tinfoil does not short anything…. and place it between the upgrade card and the motherboard… the upgrade card may of had some rf shielding at one time, but might have been lost in the shuffle...

[JAG]

Well, that didn't work.

I made a shield of double layered aluminum foil between two sheets of paper and placed it between the motherboard and the CRT with no benefit.

Put the original CPU in and all is well.

Frustrating.

Might have to throw this this in the trash heap.

[uniserver]

pull the network card just to see if maybe that is causing the issue….

[uniserver]

it could also be a capacitor some where that with the stock parts installed its fine, with the upgrade installed may increase the demand on a old semi warn part that is now creating some irregularity,