2010-06-05

SBC6120 - Casing (II) and power supply

I finally got my hands on the power supply of a _DEAD_ External Hard Disk that suited the purpose of powering my SBC6120. Before I was using a Compact Flash to IDE adaptor and I only needed a 5V supply but I wanted a "real deal" IDE drive.
My first try was an old drive I had around, a Seagate 89MB... unfortunately another case of R.T.F.M., disks with CHS addressing (cylinder, head, sector) are not supported, only the (relative) recent LBA (logical block addressing) are. Alex gave me a 3GB drive he had "hanging around" somewhere in a box, probably more than enough to hold all the source code ever produced for the PDP-8... It fit the case, just... probably too "just".
I still need to pack inside the case: a switching power supply (LM2575, two big caps, a diode and a fat inductor), the power connector, the IDE ribbon cable, the serial port connection, the power switch and (if possible) one or two front panel indicators (power on and disk activity).


The Case is a Hammond I bought some time ago for this project, but I never found a suitable power supply. Now with the external 12V supply and (this is a forward reference) the toner transfer PCB method, I can build a middle PCB board holding the hard disk, the CPU board, the switcher power supply (12V to 5V) and a power switch. I'm looking for switches like the one above, but I still haven't found a good right-angle-PCB-mounted... I'm looking at some lever switches from C&K, they look the right "age" for a pdp-8 simile. but will see what I can get my hands on...
Space in the box is tight so I still haven't decided where to put the power switch an a power LED, or if I just make some openings in the front panel and extend the LEDs on the board... I'm also looking for some front and back panel design...
There's a lot of mechanical engineering ahead... I love the smell of a challenge in the morning...