On 7/28/2020 1:43 PM, Brent Hilpert via cctech wrote: > > Per the OP's machine, the early HP21xx machines were based on CTµL, for which the main supply is +4.5V. > DTL and TTL chips in these machines ran off that 4.5 supply. > The DTL I referred to in my posting are in a third-party (IOMEC) disk controller, not the HP 2114 CPU. JRJ