Laney LC15 repair

   The laney lc15 tube combo is a pretty nice little tube combo. It's really compact(the size of a marshall MG 15) and portable. It has 5 tubes in it(!), 3 x ecc83 and 2 x EL84 Chinese made. The stock speaker is a 10inch one but it's quite efficient.
  Also, the preamp circuit is similar to a JCM800 and so the lc15 can produce some really good rock tones when the gain is set to max.  Personally, I would modify this amp to a JCM900 circuit in order to go a little higher in terms of gain, lead and distortion but that's not the purpose of this repair.
   The symptom: the volume of the amp would drop/fade out a bit after a few hours of operation and that's usually a sign that a tube is gradually going bad.  But that's not always the reason an amp fades out while you play (it happens to solid states too...).
  So I opened the amp to check everything and cleaned the board and the pots with some contact cleaner. I also checked the input jacks for signs of wear. In some amps, the fx loop or input jacks are the ones to blame for weird volume drops.
  Then, I fired up the amp, biased it properly and looked closely at the tubes for signs of arcs, hot red plate,  no or little glow. The V1 ecc83 valve seemed suspicious due to its glow and some burn marks on its glass. So I replaced this one with a TAD ecc83s and the amp performed OK. Nevertheless, it's advisable to replace all tubes if possible to ensure that the amp won't stop working in a live situation or at a gig,  when you most need it to work properly!
  Remember to bias your amp's power tubes every time you change them and once you notice anything weird. Tubes change their characteristics after a few months of operation, so you should check the bias once a year to ensure the amp's working properly and prolong the life of your tubes. Biasing the amp when it's brand new, right out of the box, is also a good thing to do. That's because the quality control department of a mass production industry can't just take the time to bias properly, check, double check, try for a few hours and rebias every amp that leaves the plant.