Test for KR 842VHD tubes

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Testing KR 842VHD Tubes

I just purchased three used KR 842VHD tubes and tested them on my Hickok 539A tube tester. The results suggest that one of the tubes tests good and two test below minimum. In addition, one of the below minimum tubes appeared to be unstable, with the reading dropping.
Kara Chafee gave me the following settings to use for the 300B:
Type Fil Bias Sel Shunt Press Min. (65%) Ave. Mut. Cond. Scale Remarks / Notations
300B 5 15 JR-3200-0 87 P4 2,990 4,600 D Kara email
Using these settings, I tested the three KR 842VHD tubes twice and got the following results:
Tube 9550 3,900 (86.3 mA), second test the same
Tube 9488 2,500 (69.3 mA), second test the same
Tube 9298 2,400 (48.0 mA), second test 2,400 and dropping, test terminated at 2,100
I also tested some of my other 300B tubes and got readings above the minimum for all but one tube, an old, much used AVVT. Here are the results:
Type Brand Test Results Plate Current mA Comments
300B AVE / MIN 4,600 / 2990
2 TJ 300B black base 3800 / 3700 85 / 84
2 AVVT-C37 3800 / 3600 77 / 76
2 AVVT-C37 3350 / 2600 76 / 70 2 Western Electric 4300 /4700 88 / 83
2 Valve Art titanium 98C 3750 / 3600 74 / 68
2 Vaic VV 30B 4300 / 4600 78 / 82
2 Kron VV 300B 3500 /3500 88 / 85
KR 842VHD
# 9550 3,900 86.3
# 9488 2,560 69.3
# 9298 2,400 48.0 needle dropping, terminated test at 2100

I sent an email to the dealer who sold the tubes originally, giving him the information above. He wrote back that the 842 needs almost 2 amperes heating current, whereas the 300B needs only 1.3. He suggested the test would not be a good one unless the heating current was increased.
It is not obvious to me how to increase the heating current setting for these tubes. Can anyone suggest what settings to change to do this?
Also, it seems to me that even if the settings used are not the exact ones to use, that the results certainly indicate to me that one of these tubes is probably good, one may be marginal at best, and the one with the dropping readings is on its way out. Any comments on this? Thanks.

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Topic - Test for KR 842VHD tubes - Rick R 15:00:03 04/10/07 (1)

Re: Test for KR 842VHD tubes - JoKath 21:08:20 04/10/07 (0)

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