Hi Levente,
If you are OK reading a circuit diagram and can search out and identify the pin-outs for the valve bases then one of the quickest and safest ways of identifying components such as capacitors is to use a diagram for your machine.
Here is a link to the manual which I think covers your machine:
http://www.morphet.org.uk/ferro/s2docs.html
New capacitors are fairly cheap and 're-capping' an old set like this is pretty much standard procedure. Remember that capacitors may appear ok when across your DMM leads but may 'leak' when under the stress of hundreds of volts.
Hope this helps.
Bill