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I also like other aspects of your battery eliminator - have you put it elsewhere on the forum?
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Al,
Only as part of other articles. I have only made two battery eliminators, the other one is in this article on page 23, again three pages from the article end:
http://worldphaco.com/uploads/UX-171...amplifier..pdf
It has a -44 and -13.5V bias supply and again it required the same protection, to stop the pass transistor failing if say the -44V got accidentally shorted to the -13.5.
Another important thing for battery eliminators I think, there should ideally be an over-voltage protection system on any electronically controlled regulators to run valve filaments/heaters. Battery valves often have pretty fragile filaments. Shunt zeners/TVS and fuses are ok. It is a real shame to take out vintage valve heaters if an electronic regulator or sub circuit fails.
Of course in valve testers, there is always the opportunity for the operator to make an error and select the wrong tube/voltage.