This system came into Kenett Classic for repairs. The customer described how the disk does not boot. Click image for larger view.
Here is a photo of the Persci 277 dual disk drive with the cover removed. Click image for larger view.
The system came with a Processor Technologies Sol System Video Monitor, something I had not seen before. Click image for larger view.
Next - Determine if the ROM is configured for Tarbell disk controller, it looks like the ROM was recently replaced. Could be that the ROM's B command is not finding the drive through the controller. The voltages on the disk controller are on the surface ok.