[David Simpson]

Thanks Nick for your participation. Hopefully another valve testing fella will get in touch with you.
Just noticed - the picture labelled "monitoring grid voltage" should read - monitoring heater voltage. By the way - it shows my NEWLEC(AVO) DMM, I love it.
On all VCM's & testers I suspect that the Heater transformer windings do load up, resulting in possibly lower than expected heater AC voltages under high heater current conditions. On AVO valve holder panels - H+ & H- can be read off the wee Top Cap connector panel, or off any unused valve holder. Remember - whatever code is set to say an IO valve holder - the same connections are made to any other 8 pin, or 9 pin, valve holder. Folks - if a B9 valve breaks down - don't throw it away - gently break the glass & remove the gubbins inside, then connect leads to all the 9 pins for connection to a banana plug socket box, or whatever. If you're making a B9 ext box - fit ferrite beads while you're at it, and fill the valve base with araldite - should last a lifetime.

Regards, David