pictured here is part of the output of a Veronica 150W transmitter (late 1990s I think!) and not used for some time since the fault below

http://i66.tinypic.com/f4438n.jpg
http://i68.tinypic.com/10p4tw1.jpg

as can be seen one of the 22pF capacitors (one of a parallel pair to ground) failed (burnt), went short circuit caused a BANG, short circuit cleared itself (as transmitter still going when hurriedly switched off)
Obviously the capacitor has to be replaced before this TX might be powered up again.

What voltage rating would this have had? (says 22+/-0.5 PF but no mention of voltage)

Anyone recommend a satisfactory replacement(s) (for the required voltage rating, tolerance and for VHF transmitter output use etc )

Would it be prudent to replace all the other similar RF capacitors in the transmitter output as well ?

500v silver mica capacitor will do the trick, the remaining caps should be ok if they haven't burnt out, farnell sell them for around £1.20 each.

i would be on the safe side and get the highest voltage rating you can 500 - 600 volts , having said that i've used low voltage caps in a valve rig that runs on 400 volts.

Shorty has the right of it there, that's a dipped silvered mica cap. Check everything on that before powering it up again, you know yourself - the solder joints after the capacitor and the trimmer on the output etc. - better safe than embarrassed!