26-02-2015, 10:59 AM
Standard solution for HK voltage problems is to run the heaters from a separate winding. Either floating or tied, loosely or otherwise, to cathode voltage.
The 6080 dual power triode can take 300V HK. http://www.r-type.org/pdfs/6080.pdf They were widely used as HT series stabilisers where the cathodes would be at a full HT. I suspect they will be expensive.
Another approach is to stress test the HK insulation on some PL81s and see what happens. They're cheap enough. They are also inherently pretty tough to survive their normal job and typically live close to the top of heater chains where the HK insulation matters.
The 6080 dual power triode can take 300V HK. http://www.r-type.org/pdfs/6080.pdf They were widely used as HT series stabilisers where the cathodes would be at a full HT. I suspect they will be expensive.
Another approach is to stress test the HK insulation on some PL81s and see what happens. They're cheap enough. They are also inherently pretty tough to survive their normal job and typically live close to the top of heater chains where the HK insulation matters.
www.borinsky.co.uk Jeffrey Borinsky www.becg.tv
