Thanks very much everyone for your help.
Scott
alwalt is right, both channels use the EL84 poweramp tubes. If you get a problem with an amp its good practise to try and find out what is causing it and you can't do that if you change all the tubes at onces.
Pound to a pinch of snuff its the EF86. Channel 1 uses V1 and V2 (ecc83's) and Channel 2 uses v3 alone (EF86). Both channels combine to use all the remaining valves. V4 is the PI (ecc83) that splits the signal to the two pairs of EL84's (v5-v8).
Trial and error with replacement new valves will tell you whats wrong, but you need to do it in stages.
Pound to a pinch of snuff its the EF86. Channel 1 uses V1 and V2 (ecc83's) and Channel 2 uses v3 alone (EF86). Both channels combine to use all the remaining valves. V4 is the PI (ecc83) that splits the signal to the two pairs of EL84's (v5-v8).
Trial and error with replacement new valves will tell you whats wrong, but you need to do it in stages.