OTTO-1 Tester

Tech Square

Technical and speculative discussion of amps, cables and other topics.

Question....

I was testing (21) different 6SN7 tubes on my Otto-1 Tube Matching device and all of the tubes were giving me 2.2ma or 2.3 ma per section while me EICO 667 was showing Mutual Conductance variations between triodes.

So I carefully lifted the 6SN7 tube base and measured the voltage being applied by the OTTO-1 tester and found the following.

The DC test plate voltage is 150 VDC... so far so good.

But the Grid test voltage is -14 VDC.

Isn't this tube in practically a Cutoff condition ?

One look at the characteristic curves for a 6SN7 tube and at 150 Volts, -14VDC it's pretty much a closed valve.

Why would this tester be designed this way? Am I missing something?

Every darn 6SN7 tube I test gives me 2.2 or 2.3 ma

Cheers,
Richard

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Topic - OTTO-1 Tester - shermanr@prw.net 07:44:29 02/11/10 (0)

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