Re: Yes, yet another home made valve tester.
I recently experienced a similar problem with some 954's on my tester.
I had made up an 'acorn' adapter to octal plug with short, direct wiring to g1,a and k, each lead no longer than one inch. The tester's socket has all round ferrite beads right up to its pins.
Even so, all my 954's immediately broke into spurious oscillations from ~600MHz upwards, with symptoms very like AdrianH's. The total cure was adding a ferrite bead threaded on the g1 lead right up at the valve pin, same for the a lead.
To be honest, I hadn't thought a 954 could get up to 600MHz with such short wiring in a lossy situation. We live and learn.
Hope this helps, Marty
|