Design changes for Virtual 2315 Cartridge Facility

AS IT WAS DESIGNED, V2315CF IS ALWAYS POWERED ON

The existence of the motorcycle battery and its charger/maintainer will keep the Virtual 2315 Cartridge Facility (V2315CF) main box powered as long as the battery remains charged. That is, as long as the main power plug to the IBM 1130 is connected, even if the system is turned off, the battery is getting some charging even as it is powering the V2315CF. 

Also, if the Fault light comes on, the V2315CF stays latched in that state until power is cycled. This would take many, many hours with the IBM 1130 unplugged with the current design. Clearly, we want to have it turn off when the IBM 1130 is powered down, but it must maintain some power long enough for an emergency unload of the cartridge image if one was loaded. 

The solution is a time delay relay, one that I configure so that when the +12V power from the IBM 1130 comes on, a relay closes. It will remain closed for a time duration N when the +12 from the 1130 shuts off. I can adjust N with a wide range, but it only needs to be long enough to allow the V2315CF to finish its unload that begins when we see the power drop. I believe that two minutes is plenty of time. The relay hooks the battery to the system, so that battery is removed two minutes after 1130 system power turns off. 

UNLOCK LAMP CONTROL DURING VIRTUAL DISK MODE

When we are the normal real disk mode, the 13SD disk drive inside the IBM 1130 is producing the Unlock drive to the main console Unlock lamp. My interface board watches that Unlock drive signal in order to control the Unlock lamp on the V2315CF and to control the state machine in the PICO. It should be able to turn the main console Unlock lamp on and off when we are in the alternative virtual disk mode. 

The main console Unlock lamp has +48V on one side. Inside the 13SD drive, an unlock solenoid is also connected to +48V on one side. The other sides of the lamp and the solenoid are connected to an open collector circuit in the disk drive than can ground the lamp and solenoid when the drive should be unlocked. 

My original design, which does not do the correct thing, would ground the lamp and solenoid to turn both on even if the disk drive was not asking for it. That could be dangerous in a particular case - if the unit is set to virtual mode, but the disk drive was powered on, then the operator opens the handle while the cartridge is spinning. 

I will have to instead switch the lamp wire to either the disk drive or to my MOSFET circuit output from the interface board, depending on the real versus virtual mode of the machine. I will implement this on the interface board, using a relay to switch the wiring and the MOSFET to ground the lamp when switched to the virtual mode.