So a power conditioner would help.
Is 240 V the nominal mains voltage in your country?Bernd
In UK it's now supposed to be 230 V +10% −6% since EU "harmonisation". In practice the average is 240V. I've done my testing when the voltage has been high so am happy now 
Thanks very much for your help - on to woodwork now to build Cabs !
Steve
Hm,
that's not so much difference but it should be possible to adjust it even below 35 mV.
What neg. voltage do you measure at the junction of R45/46 and to what negative maximum is it adjustable by VR9 (10k bias pot)?Bernd
Sorry, you wrote already that you have -24V - but it is across VR9 and R63, isn't it?
No - at VR9 to R63 I have -8.7V, at VR9 to R46 -25.3V and at R51 or R52 I have -34mV tonight - With Mains voltage of 241.5 - It varies between 235 -250 Here so readings change depending on time of day/night 
Hi,
most of the heavy duty resistors are specified at rated power for a surface temperature of 120...180 °C. So you have them to mount safely.
BTW What voltage du you now measure?
Bernd
Hi Bernd - got 6.1, mains varies here 
Other slight thing is at bias pot I have -24V but cannot get any lower than -37mV accross R51 or R52 - is that OK?
Thanks
Steve
No,
that doesn't work. You forgot the resistance of the heaters themselfs which is in parallel to Rb.
A simple series resistor will do:
(7,4 V-6,3V)/2,1 A = 0,52 Ohms with a power rating greater than (2,1 A)²·0,52 Ohms = 2,3W.
Try 1R|| 1R or 1R
1R2 each minimum 2 watts or 0R47 or 0R56 minimum 5 watts.
"||" means "in parallel"
Bernd
Hi Bernd - thanks for that, I used 2 1R 3W in parallel - they get very hot though - too hot to touch - is that OK?
Hi - I'm in the UK and just finished an A15MK2 - It works but the heater voltage is too high at 7.4V. Is it OK to use a voltage divider circuit, using 6K8 Ohm and 47K Ohm 2W resistors wired like this
[ATTACH=CONFIG]9486[/ATTACH]
Where Ra is 6K8 and Rb is 47K - It should give 6.46V
Thanks
Steve
