How much HV and 6.3v heater current are available in the 300B? (nt)

[keto]

:-)

[Paul Joppa]

The stock power supply produces a nominal 460 volts DC at 80mA, with a 120v 50/60Hz primary supply. The voltage increases fairly linearly to 490v at 50mA. This winding and the primary are responsible for most of the heat generated.

The 6.3vAC winding is nominally rated 1.2 amps. That's a conservative rating, but I have not explored where the limit is or how it interacts with the other windings' heat generation. I cannot recommend exceeding that rating.

[keto]

Super. Could the new soft start 5670 circuit be modified to handle as much as about 20mA total, say 10mA SR + 2mA C4S and 8mA voltage amplifier? I'd like to try the 6SN7GTB both as a "shunt-regulated and C4S-ed driver" and as a "SR and choke-loaded (MQ EXO 010) driver". Or would it be better to get the soft start 5670 circuit and a blank board and work up the 6SN7 circuit separately? This would be for driving the 300B at least initially. Thanks!

[Paul Joppa]

The board does not have room for heat sinks large enough for the higher current. Ask me again in a few months and I should be able to be more clear on the possibilities, btu right now I have a bunch of family/medical issues that are taking a lot of my time.

[keto]

Thanks a lot for the info, Paul. All the best, --keto