BA23 Power Supply

<Linear/mains frequency supplies normally have internal links (or if <you're lucky an external switch) to select the voltage. AFAIK, DEC <always used transformers that were big enough to work at 50Hz (and were <fine on 60Hz as well, of course). Th BA23 (and 123) PS is a really wide range unit. For 120 nominal, the working range is like 85 to 140V and for the 230 nominal it's 180 to 260 or so. <Ferroresonant supplies (RX01, RX02, some RK02/RK03 systems) are a pain. <IIRC, there is no way to convert the 60Hz version for 50Hz mains short of <a new transformer. Fortunatly they are limited and the PS can be subbed out easily. the induction motors used are also part of the problem. <One other thing remains. Most PDP11s have what's called a 'line time <clock' -- basically an interrupt every mains cycle. This is counted by <the real time clock program in most OSes, and used to keep real time, <etc. Of course if you move a machine from 60Hz to 50Hz power or vice <versa, the real time clock will run slow/fast until you re-SYSGEN the OS <for the appropriate frequency. This is not a big problem -- things still <work -- though. If your really bugged by it you can supply your own LTC derived from other sources. <So in your case. The PSU will be fine if you flip the switch. The machine <should work (everything inside the box runs off the DC outputs of the PSU <and doesn't care about frequency). The real time clock may run slow. Also depends on the CPU board used as some use the TOY clock for LTC. This does not include the 11/03, 11/23 series. The 11/73 series I can only speak on the KDJ-11A I have and that uses a traditional LTC like the 11/23. Later ones may differ. I cheat and synclock a 300hz osc to most submultiples 50/60hz then divide by 5 to get 60hz. Trivial circuit, predictable result. Or take a crystal and divide to 60hz (or 50 if thats what you need). Allison