[Kenwood] TS530 Bias missing.

[John Tait]

A friend of mine has a faulty TS530.. He says there's no grid bias on the final tubes, so they "take off".. He's bring it to me to check it out.. Is there a "usual suspect" for this fault on 530s??
  Tks es 73
        John EI7BA  http://www.iol.ie/~bravo/