PET power supply questions

-----------Original Message: Date: Sat, 12 Jan 2008 23:51:21 +0000 From: Ethan Dicks <ethan.dicks at usap.gov> Subject: PET power supply questions Hi, all, I've been collecting various classic bits to work on over the winter, including a pre-CTRC 32K PET board (2001-N/3032) and a Static PET board. I don't have any cases or accessories, but I do have a C2N232, a single bare keyboard, and a C=Key converter enroute. For video, I was planning on trying that ancient XOR circuit to make composite video Obviously, I'm unlikely to find a suitable mains transformer, so I was going to cobble up some form of switcher that puts out enough of the right voltages to make this all work. Poring over the schematics for the 2001-N board on zimmers.net (e.g. 320349-9.gif), I'm guessing that the onboard regulator circuit is pumping out +5VDC at over 5A, +12VDC at a couple of amps, and a miniscule amount of -5VDC. I'm not running a real tape drive, so I'm not as worried about the +9VDC unreg. Does anyone have any reasonable estimates or real-world measurements for the current draw on the various supply lines? Has anyone out there ever gotten a PET to run from externally regulated DC? Thanks, -ethan ------------Reply: I haven't done it but, since I've also got a board and lower case w/kbd & cassette but no monitor or PS xfmr, it's also on my to-do-someday list to put it together with a small switching supply and composite monitor. I don't have a DRAM 2001N, and it's a little awkward to check the current on my 8032, but an SRAM 2001-8 identical to the one I sent you (but with chips;-) draws 2.8A on the unregulated 8.5V which feeds 4 LM305s, so the actual 5V draw would probably be slightly less. I'd think that any common +5/+12/-5 supply with >5A on the 5V would do just fine for both your boards, and if you don't need the cassette a single 5V supply would do the SRAM version. mike