Two weeks ago I wrote to E-MU support ( [email protected] ) asking for the rack ear screw spec. As of today still no reply. Ugh. So after a week waiting, I tried to figure it out myself.
Pulling a screw from one of my E-Mu units, I measured it with a digital micrometer. I was pretty sure it was a #6-32 1/4" long pan head but it might have been a #5-40 1/4" long pan head so I ordered a few of both sizes off of eBay to be sure.
The screws arrived today. Turns out the the screw is in fact a #6-32 1/4" long pan head screw. Then I realized I already had a bunch of them in my computer repair junk screw box. These screws are the same size screws that are used to screw in a standard 3.5" computer hard drive. Some screws I found were longer than 1/4" but I had plenty of the right size. Problem solved.

My MIDI rack. The Proteus 2000 & Virtuoso 2000 all have 4 ROMs each in them.
The Proteus 2000, B3, MoPhatt, Orbit 3, Vintage Pro, Virtuoso 2000, and Audity 2000 rack ears are no longer available from E-Mu/Creative and sold out at least 10 years ago. I needed two rack ears 3 years ago and it took me a long time to track them down. A real long time. The good news is there is a seller on eBay now selling new replacement E-Mu rack ears. The bad news is that he is charging $60 a pair shipped from Thailand. I paid $30 for a used pair 3 years ago and thought that it was way expensive back then for a part that E-Mu had sold new for $7.95 per PAIR. But at least it's an option if you need to rack mount an E-MU sound module
I posted this so that anyone else who needs screws for E-Mu rack ears can find this and not have to wait for E-MU to reply (maybe never).
