Indigo 2 - no video.

I just got a "teal" SGI Indigo 2. Problem is, I get no graphics output. When I turn it on, the LEDs on keyboard flash once, the LED on the I2 turns on, after two seconds turns off, then turns on again and stays turned on. I hear the boot tune. Monitor is SGI 20E21, connected via 13W3 cable, but it gets no signal (or at least no sync) from the machine. Manual says something about "dissonant piano chord" - how is it supposed to sound like? One thing I've verified that without graphics card the chord sounds the same. NumLock LED on the keyboard does not light when i press that key. Is there some way to reset the NVRAM or something like this? Note that there are no SCSI disks installed - the bays are empty. -- If you cut off my head, what would I say? Me and my head, or me and my body?