SA-1000 Known Issues  
 
  • Failed Output Stage
    The itty-bitty TO-92 Siemens BSS101 MOSFETs used as source followers after the line stage tube fail on rare occasion. If you cannot find this exact part, then the Zetex ZVN4424A is a good replacement (TO-92, N-Channel, 240V). I recommend replacing the right and left channel MOSFETs at the same time to keep then two channels identical. www.digikey.com carries Zetex parts.