pichotjm <pichotjm at free.fr> wrote: It is not always necessary to go to the expense of buying a 25000 series chip. I found some WOM in my Dec Alphaserver 1000A recently. I'm not interested in this bleeding-edge stuff (besides its too new to be on-topic here) so I have now replaced it with some ordinary memory. I wonder if I could get a good price for the WOM on ebay? 6.3Vac is a common voltage for valve (tube) filaments. Given that the 25000 series is implemented in VLSI (Vacuum large scale integration), I suspect Vff is the supply to the filaments for the integrated valves on the WOM chip. Decreasing Vff should reduce power dissipation and improve the lifetime of the chip. However, it may also result in poorer noise immunity. Either that or Vff is the reference voltage used by the flip-flops and decreasing it will unbalance the chip by creating an excess of flops over flips. Typically, these things are designed for the American market with no thought given to widely used standards in other parts of the world. I suspect we will have to use motor-generator sets to power this type of circuit. Solid state frequency converters will not be suitable for the critical power requirements here. Regards, Peter.