On 7/28/2020 1:43 PM, Brent Hilpert via cctech wrote:
Per the OP's machine, the early HP21xx machines were based on CT?L, 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.