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Old 17th Jun 2020, 1:59 pm   #28
Bazz4CQJ
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Join Date: Apr 2009
Location: Oxfordshire, UK.
Posts: 3,450
Default Re: Yes, yet another home made valve tester.

Sometime ago I built a little unit to do DC characterisation of ECC81's, which is my preferred valve for use as a standard for my AVO163. It soon became apparent with the MkI version that it would sometimes spring in to oscillation, but it settled down with maybe 6 or 10 beads and maybe some decoupling caps, all built in to a diecast box. I think I may have used some feedthro caps on some of the feeds from the external PSU and external meters. It seemed to me that valves with a Gm of more than 4 or 5 were particularly prone to oscillate, as might be expected.

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