IBM AS/400 B-Series in 23 (1998)
When their other computers prove to be inadequate the guys buy a second-hand "PDP-11", in fact an AS/400, to help them crack passwords, but are unable to use it because of a lack of three-phase power and air conditioning.
Well it's not a PDP-11, but even given that the AS/400 would have been more or less new when this film was set and buying one second hand would not have been feasible.
Actually, this could be any AS/400 from the B/C/D/E/F series, which was made between 1988 until the architecture was overhauled with the RISC-based models in 1995. It's extremely likely that this machine was a second-hand AS/400, because around 1998, IBM was cutting off support for the B/C/D/E/F line in favor of the black-colored RISC models, which led to many companies upgrading to newer AS/400 equipment, leading to a large supply of second hand AS/400 equipment at the time. Hope this helps.
I find this to be humorous, as MY AS/400 requires 220 single pase and a windo fan when the room gets too hot...
In the German original the computer is unusable in the first place because it's damaged and Karl's domicile lacks a air-condition. The problem with the current supply is based on a 32 A, single-voltage-supply of the computer; older buildings as seen in the film normally have 12 A or 10 A fuses. I think the three-phase issue is a misunderstanding of the term »Starkstrom« (meaning “high-current”) This term was a normative term for all voltages below 1000V except extra-low-voltage until the year 2000 and is used for three-phase-supplies in colloquial until today.
@Landon Rodgers, The movie was made in 1998 but the story takes place around 1986-1989. Hence the anachronism. By the way, they actually want to buy a micro pdp 11 (something like this I guess: http://www.computinghistory.org.uk/det/39684/Digital-Micro-PDP-11-53/) but the computer was sold and the seller suggests the old model instead ("the same, just a little bigger") Not only the computer couldn't work because of the voltage and air-conditioning but also they realize a part is broken when they arrive at home. It's a funny scene.