Interesting, good to know! -- Anders Nelson
On Tue, Jun 9, 2020 at 1:04 PM Ethan Dicks via cctalk <cctalk@classiccmp.org> wrote: > On Tue, Jun 9, 2020 at 10:46 AM Jon Elson via cctalk > <cctalk@classiccmp.org> wrote: > > On 06/09/2020 09:27 AM, Anders Nelson via cctalk wrote: > > > Related question: Is there any reason, other than historical accuracy > and > > > cost, to not replace the power supplies in vintage computers with > modern > > > switching power supplies? > > > > > The old discrete transistor machines often used fairly odd > > voltages, not like 5V and 12V. > > DEC's transistorized machines used +10V and -15V supply rails for the > logic, and some other large voltage (+28V?) for the core. > > Later machines still used odd voltages. Lamp-based PDP-8 front panels > used voltages like +8V, and later core was IIRC +20V. > > There are a couple versions of the PDP-8/a PSU, for core memory and > for MOS memory. MOS memory is standard 1970s triple-voltage stuff > (4096s and 4116s) but they pull a lot of +12V compared to later > machines. > > It's often easier to just fix the old PSUs than replace them. At > least linear supplies aren't so hard to debug. > > -ethan >
