Thanks everyone....
Gents,
The point about using current regulation is a good one. If one is going to use dc on the filaments, many say that current regulation is prefferable to voltages regualtion. But the point of my inquiry an attempt to implemet ac heating on a 'universal', inexpensive basis, i.e. with tubes that are not in current production, it would be nice to be able to plug in tubes of differing heater requirements, but same characteristics, and have it function properly. This can be done with a the proper ac voltage and a dropping resistor -
For example, a 12v ac secondary windiing with a 16 ohm dropping resistor would give the folling % of power consumption vs specified filament consumption on the various ?CC189/?ES8s -
Type, fVoltage, fCurrent, fPwr, fPwr%
YCC189, 5.03, 435, 2.19, 93.65%
5ES8, 5.25, 422, 2.21, 87.89%
6ES8/ECC189, 6.23, 361, 2.25, 97.71%
7ES8/PCC189, 7.20, 300, 2.16 , 100.00%
PCC189(Phlps),7.35 , 290, 2.14, 93.65%
So if one seeks to run their tubes with a 5% undervoltage, corresponding to a 93.65% power consumption on the filaments, you can support, with no changes, a YCC189. 6ES8/ECC189, a 7ES8, and a Phillips specified PCC189, with no changes. Like current regulation, this only works for a single ac winding per filament.
A Russian site, guitar.ru indeed has that 7.2 voltage spec, as does my page from the VadeMecum. When these tv tuner cascode tubes were produced, 1963+, I believe Phillips was the 'big dog' on the block, essentially controlling, Mullard, Brimar, ... So as Phillips went so went the world.
Thanks all