PDP-11/70 Boards

-----Original Message----- From: cctalk <cctalk-bounces at classiccmp.org> On Behalf Of Mike Katz via cctalk Sent: 08 December 2021 22:58 To: General Discussion: On-Topic and Off-Topic Posts <cctalk at classiccmp.org>; wrcooke at wrcooke.net Subject: Re: PDP-11/70 Boards More accurately up to it's rated wattage "Power = Voltage * Current" after all. If you have a 100W max variac you can draw 20A @ 5V (approx) but only 1A at 100V.

On 12/8/2021 4:44 PM, Mike Katz via cctalk wrote: > "As a general rule, a variable transformer (Variac) can provide full > rated current at any output voltage. So a 2.5A unit can provide 2.5 A > at 1V, 10V, 120V, etc. With a 20V output, that is 50 VA (Watts, sort > of)." > > Up to the current rating of the variac. When you draw more current > than the transformer can deliver then the voltage will sag. > > On 12/8/2021 4:22 PM, Will Cooke via cctalk wrote: >> >>> On 12/08/2021 3:58 PM Rob Jarratt via cctalk <cctalk at classiccmp.org> >>> wrote: >>> So, to supply the bricks on the bench, would a variac rated at 2.5A >>> be OK? I am not sure I know how much current the bricks will draw at >>> 20VAC, and at what voltage the 2.5A rating is given. Otherwise, >>> would this do the trick? >>> https://cpc.farnell.com/block/steu250-48/transformer-250va-230-400v- >>> 2-x/dp/TF01418?st=24v%20transformer >>> >>> Thanks >>> >>> Rob >>> >>> >>>>> JRJ >> As a general rule, a variable transformer (Variac) can provide full >> rated current at any output voltage. So a 2.5A unit can provide 2.5 >> A at 1V, 10V, 120V, etc. With a 20V output, that is 50 VA (Watts, >> sort of). >> >> Will >> >> "I was born not knowing and have had only a little time to change >> that here and there." >> Richard Feynman >