Ibanez TSA15 head retubing and setting the correct bias

[Nemeske]

Dear Forum,

I have been asked to retube an Ibanez TSA15H tube head amp. Could someone help me how is it done correctly? I received the amp with a set of replacement tubes (2x 6V6 S and 2x ECC83 S)
I've read somewhere that it has fixed bias, so maybe nothing could be done except replacing the tubes.

Thank you for your help in advance!

 

[petertub]

It has "fixed bias" and adjustment but seems to lack possibility to measure idle current. ( one could of course add a
currrent sensing resistor in series with the cathodes) See the attatched schematic

 

[Nemeske]

Dear Petertub, thank you for the schematics, I found it useful!

 

[Nemeske]

I've just replaced the tubes (the powers was a bit of a hassle as the repacement JJs were taller than the TAD's so had to put them place in situ) Other than setting the bias to -30Vs, I've done nothing. Sounds ok.