I think the "A" board is a later version. Back in the '90s, I had two IIsi machines. First one had the darker green board installed. It also had problems with both the contacts for the speaker and power LED, and the contacts on the fan, the latter of which were what killed the board. Fan stopped working, so, like an idiot, I tapped the fan downward while the machine was running. Fan started working, but, the machine crashed at the same time. Never booted again. Suspect the contacts shorted out the external SCSI connector and may've fried the SCSI chip. The replacement machine had the earlier board with the lighter green color to it. That one, strangely enough, had no problems with the speaker or the fan. Also had a nicer case. Moved my 230MB hard drive over to it, added 16MB of RAM, bumping it up to 17MB, and continued using it for another 1.5 years, before I picked up a IIci. At that time, it went to a friend, as a 5/40 machine to replace his dying Classic.