This Doctor Who story, written by Philip Martin, was first broadcast in two episodes in 1985.
While repairing the TARDIS console, as Peri complains over the freak accidents he caused since they left Telos (Attack of the Cybermen), the Doctor finds that the TARDIS has unexpectedly stopped in the middle of deep space and he can do nothing to fix it. Peri locates the TARDIS manual and presents it to the Doctor who quickly dismisses it, as he knows perfectly well that transitional elements within the TARDIS have stopped producing orbital energy only Zeiton-7 ore can realign the power systems. But as the Doctor explains, Zeiton-7 is exceptionally rare and only comes from one planet in the Cetes constellation: Varos.
Vengeance on Varos is available on DVD.