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G8UWM-MildMartin · 19th Sep 2020, 2:39 am

OK, either of those ideas with a pair of resistors across the original filament supply to create an artificial centre tap for the cathode. I expect it has been done decades ago, but I can't find any info.

I've seen mention of a triode-strapped KT66 having the right characteristics and it being the UK answer to the 6L6, and the very cheap 6P3S (Cyrillic: 6П3С) being the ex-USSR equivalent to that

How's about a forum project to design and test some reasonable PX4 substitutes?

It might help save some decent sets and radiograms.

19th Sep 2020, 2:39 am	#4
G8UWM-MildMartin Heptode Join Date: Jan 2004 Location: Stockport, Greater Manchester, UK. Posts: 827	Re: PX4 substitutions OK, either of those ideas with a pair of resistors across the original filament supply to create an artificial centre tap for the cathode. I expect it has been done decades ago, but I can't find any info. I've seen mention of a triode-strapped KT66 having the right characteristics and it being the UK answer to the 6L6, and the very cheap 6P3S (Cyrillic: 6П3С) being the ex-USSR equivalent to that How's about a forum project to design and test some reasonable PX4 substitutes? It might help save some decent sets and radiograms.