[morzh]

Start with recap.
Address transistors only if needed.
Testing transistors is simple and is best done with an analog ohmmeter.
If it is a PNP, then:

- Unsolder two wires that are not connected to the case (the pins). In case all three terminals are insulated pins, unsoder any two.
- Locate the terminals designations: E, B and C.
- Set the Ohmmeter to "x1"
- With Negative lead (Negative does not necessarily mean black or Common: on old analog meters Common may carry positive when used as Ohmmeter; you could determin this with another voltmeter) on B, touch the Positive lead to C and E. There should be finite value of tens to hundreds Ohm measured in both cases.
- Switch Ohmmeter to x100
- Now reverse the polarity: connect Positive to B, and touch Negative to C and E. There should be no needle movement at all. The BE and BC junctions should be fully open.
- With the Ohmmeter set at the same range, touch CE with the leads, first one way, and then in reverse.
There should also be no needle movement.

Note. Make sure your hands to not touch probes' tips at any time - otherwise you will see some conducting when you should not.

Any of these not met, the transistor should be replaced.

Note: this does not test for "Beta". This is usually not necessary as transistors that have their junctions intact do not deteriorate much over time. If however you decide test for the "Beta", you need a specialized Multimeter with a socket and switch position made for it.
The static Beta could easily be measured with a couple of resistors, a potentiometer and a couple of batteries, but as I said, in your case it is likely not needed.

If however the transistors (or one of them) are bad, it then makes sense to buy a pair and replace both.
The transistors do not have to be matched well, as if both are PNP, then one will work as a follower and one as a CE (unless using a transformer push-pull arrangement which it is likely not). However making sure both have a good Beta makes sense.