Marshall reverb 12 model 5205

[Bushbaby]

Now that I have some replacement fuses (T160mA 250v), I have replaced the 2 x 2200uF 25v caps with 2 x 2200uF Nichicon UFW 63v caps. The amp is working and it does seem that the reverb unit is working albeit difficult to hear fully with a 500hz signal (slight movement of the amp and splashing sound can be heard through the speaker). The fuse has not blown with the vol and gain up although I did not have them flat out this time.
However, it still has a pop when switching off. Is this due to mains switch or do I need to put a cap across the switch??
Thanks