Better getting one of the ones from here, known history etc. Need more info on this one, like if it has Partridge transformers, not all of them did. There are plenty of issues SC120 MKIV can have, easily fixed if you know what you are up to and have the time and parts, but buying those things is expensive, mostly the knowing what you are up to part. They sound very 'valvey' and the preamp is very flexible, which does mean a lot of 'wrong' 'tones', rather than the all the knobs don't really do much EQ on a lot of valve amps.
http://basschat.co.uk/index.php?app=core&module=search&do=search&fromMainBar=1