Mahleu,
Yes - replace it!
The diagram unfortunately does not show a fuse value, but the amplifier draws about 1/2A from the mains. Thus even a 1A switch would be ample.
But there is something else with the Stereo 20 design. I have mentioned this in the past without much reaction, and probably some name-calling behind my back.
So I am treading carefully here; unfortunately proof exists.
Should anybody be interested:
There is something amiss with the Stereo 20's h.f. performance, even though it is liked by so many - or mabe because of it. A square wave reproduction shows an awful rise-performance, which could lead to conditional instability depending on the nature of the loudspeaker(s). I have refurbished 3 amplifiers (thus 6 main amplifier units) and all showed the same short-coming - thus rather difficult to accept that it was a chance mistake. I had to change the feedback phase correcting capacitor C9 significantly to correct this; can unfortunately not recall to what value. I am afraid that the Stereo 20 output transformers were not Leak's best designs; measurement shows rather excessive leakage reactance for a 26dB feedback design, hence the phase shift problems. I think there was a further change necessary, also faded from memory. Then, one has to feed the amplifier(s) from a fairly low impedance source (< 6K), otherwise the input ECC83 Miller capacitance started having further effect on feedback stability. Fortunately most pre-amps have quite low output impedances these days. I could re-examine and illustrate if a Leak Stereo 20 owner near Pretoria is willing for such an exercise.
Apology for the negativity folks, but there it is. (Being familiar with Leak amplifiers for more than a half century, this surprised me myself. His early amplifiers were gems.)
