Verified configuration of Diablo drive for use with the archiver

CHECKED OUT THE CIRCUIT BOARDS IN THE DRIVE

The drive has six logic boards inside (plus a power PCB and a backplane). By examining them I could look to see what options are installed on the drive - and whether it will work properly to read 2315 disk cartridges that had been written on an IBM 1130. None of the board numbers match the manuals available online; these appear to be older versions of the Diablo logic. 

I found one board (J1)with some wires added, which might have modified the behavior. I would need to back it out if so, bringing the drive back in conformance with the specifications. You can see a few violet wires, one end tacked to the connector on the left and a transistor that appears to have been added to the board by drilling holes. 

When I compared to the more modern versions of the board, I found the same transistor wired into the circuit in exactly the same way. I am assuming that this is a rework to add that transistor into the circuit from the previous design that was built into the board. As such I am leaving it in place. 

I looked over boards J8 and J10 to verify the options that might be installed. I did find that the drive was set up for daisy chaining. I see from the schematics that some drives were set up so that they could not, but this option also includes the support for the four signal lines Select 1 to Select 4 that determine which drive on a daisy chain will work. I also saw the jumper plug that configured this drive to respond to Select 1. 

I also saw that the drive does generate the Logical Address Interlock signal, asserted if a seek is requested to a track address that is not between 0 and 203. That might be option 064 which is for Varian computers, implementing four attention lines and the Logical Address Interlock signal. I didn't look at the attention lines since I don't need it nor care about that functionality.t around the circumference of its hub. There is one modification to shorten the sector marker pulse w

The drive does have the circuitry to report sector numbers for up to 32 sector versions of the drive. There is no way to change the machine to choose the number of sectors it supports. Instead, the Index Marker resets the counter thus it automatically supports the number of sectors that the 2315 cartridge has cuhen the drive is configured to support 32 sector disks, but it is not installed on this drive. 

I then checked board J10 for two important options. First, I verified that a 10 ohm resistor tied the Write Gate and Erase Gate signals together. If they did not, then option 008 would be installed to implement an independent Erase Gate. Second, I had to be sure that this was option 001 - 720KHz data rate and not option 002 - 781 KHz. That was determined by the value of a a specific resistor pair. If the main resistor was 9.8K then it is the wrong option, but I found the 10K value that matches option 001. 

DETERMINED CONFIGURATION IS GOOD FOR USE WITH THE ARCHIVER

It appears to have option 063 - off-white paint for Varian, based on the paint on the drive. It also has option 019 - extended mount - so that it can sit in a standard rack but have the drive extend forward about three or four inches. 

The disk heads are the metallic standard density type, not the ceramic heads you find with the high density drives. Exactly what should be installed. 

MODIFIED TERMINATOR TO MATCH THE SIGNALS I WILL USE

I started with the terminator that was closest to the version I need - it had pairs of resistors to terminate signals for all but two of the signals I will use. Using the VOM as a continuity checker, I located the open pads on the terminator where a 120 ohm resistor would pull up to +5V and a 330 ohm resistor would pull down to ground. I soldered new resistors in place at those locations and now have a fully functional terminator for the drive when connected to my archiver. 

CONNECTOR WITH RIBBON CABLE TO IDC-40 CONNECTOR

Here is the MRAC-42S connector that fits onto the rear of the Diablo drive. It is connected with a 40 wire flat ribbon cable that has a metal plate bonded along the length as a ground shield. The other end of the cable ends in a female IDC 40 pin connector (often used with internal hard disk cables in a PC).