Tube Voltage Regulator Flicker...

[Steven-H]

Interesting topic. While I don't have anything to add (my knowledge is limited...), I would like to see a schematic. I've wanted to make an 807 sort of amp for a while now...

[sonata149]

To all the members who are trying to help me sort out this problem I hope I can manage to post these 2 partial scans showing the screen grid VR section.

As can be seen, from a B+ of around 450V there is a 10K/10W dropper resistor feeding 2 VRs for 250V - an OC3 and OD3 - which is then taken to the 807 screen grid via a smaller 1K0. (Is this a grid leak dropper similar to that used for the signal grid in audio amplifiers?) There is then a 47uF/0.22uF capacitor combo from the 807 screen grids to earth (ground). I'm not sure if Kevin is referring to this capacitance.

I now realise that by halving the 1K0 resistor I didn't change the current draw of the VRs. Maybe, I need to lower the 10K resistor. Perhaps, you guys can guide me as to the value to use. The real B+ voltage is rather lower than that specified due to the slightly lower secondary AC voltage rating of the transformer I used.

I hope this gives you a better idea what I'm talking about.

Thanks and regards to ALL.
Joe A

[kevinkr]

HMMM, I'm not sure about that 47uF cap and the combination of VR tubes through a 1K resistor, but presumably other amps based on this design do work.. The 10 K resistor would result in a total VR tube + screen current of 20mA which may be rather marginal at full power - I would decrease that resistor to say 6.8K and see what happens.

[sonata149]

Hopefully I get the image posted this time.

[sonata149]

This is the second part showing how the VR supply is connected to the screen grid. The member who asked me for the 807 circuit can email me directly as I'm still being 'moderated'...