Mac Plus Black boot scene with happy mac

[unity]

This is a new one to me. I have a test Mac setup. Going through my motherboard surplus I put in another Plus with four 256k SIMMs I have been transferring from motherboard to motherboard. So they seem good. The issue is that immediately upon power up with this one particular board I get a flashing floppy icon surrounded by all black. When I put a floppy in, it reads and goes to a happy Mac with all black screen less icon real-estate. The Mac clears purrs along reading the floppy. This particular setup, System 6.0.x, is modified and asks to name the Mac. When the floppy stops reading, I enter a name and press return. Then the mac continues to the desktop based on the sound of the floppy reading again.

Obviously a video issue, but with the icons "working" right I am at a loss with this one.

Thoughts?

 

[unity]

Doh! Figured it out. The last two had the resistor clipped for 256k RAM. Guess I am getting rusty when I start to forget about those things.

 

[Ike]

Hah! I once got a 'non working, for parts' plus that had a similar symptom. Turned out to be that resistor as well.

Good you figured it out