26 Apr
2012
26 Apr
'12
1:38 p.m.
On 2012 Apr 26, at 11:32 AM, Tony Duell wrote:
The datasheet specifies AC.
Chuck Guzis
wrote:
Why does Vff have to be AC? Surely it's the rms vlaue that really
matters, so 6.3V DC would be OK too [1]. And IIRC the unregulated
output
of the mains adapter was on the expanison connector of the Speccy, so
you could use that with a dropping resistor.
[1] Vff = 6.3V nearly always implies an indrectly-heated cathode,
so the
polarity and whether it's AC or DC make very little difference. If that was the case, why didn't they go with
state of the art in
1972
and use the Signetics 25120 memory chip? --Chuck
Probably due to the inconvenience of needing 6.3Vac for the Vff
supply.