Intel MDS Series II IOC question

I think there are some Intel MDS owners here, and even some who use them! ;) Maybe one of you will know this detail. I'm trying to troubleshoot a problem on one I just got, a Series II, model 225. There is a large PC board on the back panel of these beasts called an IOC (Input/Output Controller). It contains an 8080 cpu, some ram, some rom, and basically all the I/O for the machine on the back panel. It is commanded by the system's cpu (a different board plugged into the front multibus chassis) through a couple of I/O ports, if I remember correctly. The IOC board has a three-position switch on the back. One position is "line" and in that position it is connected to the system cpu and does its everyday work of controlling the I/O for the MDS. One position is "local" and in that position I think all it does is echo characters typed on the keyboard to the crt. The third position, "diagnostic" causes it to run some internal confidence test. In that position, if everything is healthy, there are a series of two beeps, a pause, then three beeps after reset. After that there are some choices on the crt that let you run a few different tests from the keyboard. The one I'm working on will beep twice, then pause, then only one beep. Nothing further happens. No characters on the crt (which does have a raster, so at least part of the crt-controller function of the IOC is working), no apparent response to keyboard typeins. My question is this...does anyone know what part of the diagnostic is failing when there are only three beeps instead of five? The documentation I have only says it should beep five times but doesn't say what each beep signifies. It would help narrow down my search for the problem if I know what part of the test is failing. I'd love a disassembly of the firmware of that board, but I've never seen it or any source for it. That would be very helpful. Anyone have such a thing? I don't remember ever seeing anything like that from Intel, but it was a long time ago and I may have just forgotten. I'll be diving into this problem this weekend, but if anyone can help with the above couple of questions that would be wonderful. Thanks in advance! Dave Mabry