Hi Velleman
I am just testing my newly built K4040 amp. The tube biases have been set up and it can play audio into speakers fine. When I check the voltage measuring points on the PCB they all show undervoltage by between 5 to 15% but this is not unexpected as the mains voltage selectors are currently set for 245v but the actual mains input is only 232v. The problem is that the heater voltages are already measuring 6.8 v AC (at the grey connectors, all tubes warmed up). Is this normal or acceptable? I believe tube heaters are typically rated at ± 10% of their nominal voltage ( 6.3v) so they are already running near the limit. So I am reluctant to change the voltage selectors to 230v just to get the DC volts near their design value if it is going to shorten the tube life. Would Velleman like to comment whether my amp voltages are within typical tolerances or do I have a problem somewhere?
Thanks
Dave