Help interpret tube test data

[jdurango]

I sent some tubes off to my tech to be tested, and his Hickok tester wasn't able to test a couple of the bigger boys, so he tested them with a calibrated lab grade HT supply and bench DC supply. So, I'd like to sell these tubes, but everyone on fleabay seems to want a Hickok score/number. I don't know what these values would roughly correlate to. Can anyone help me make some sense of this? I've attached original datasheets for both tubes. Thanks a ton!

Notes from tech:

Tested HT supply - OK 0 to +400V, 0 to -125V. Set up test on 262A. +10V on heater, draws 0.31A per specification. Heater glow observed. Set up test with B+ via 100k resistor at 135V, C- via 2.2k resistor at -12V to -0.5V, ammeter to monitor plate current shows variation in current. Need to test further.

Tested 262B: Calculated load line, set Ebias = -4.0, HT = 135V, Rp = 20kΩ, Rl = 39kΩ, Rg = 100kΩ, coupling = 0.1/300. Heater = +10V. Input signal 0.68Vrms = 1.9Vpp. Output = 4.06Vrms. Gain = 15.5dB.

Tested 310A: Tested with +10V on heater, draws 310mA per spec. Set up test: HT = 160V, Rp = 47kΩ, Rg2 = 330kΩ, Cg2 = 0.22µF, resultant Vg2 = 83V, Rk = Rg3 = 1.82kΩ, Ck = 47µF, Rg1 = 1.0MΩ, coupling = 0.1/300. Input = 0.35Vrms, Vout = 16.5Vrms. Gain = 33dB.

 

[moamps]

The first problem is that your tech most likely doesn’t know what the measurement points used in the Hickok tester are. Therefore, it is difficult to interpret its measurement results precisely, as it is not very clear what the values of the anode voltage and the control grid were.
For triode 262 I would suggest measuring the anode current for measuring points A onwards (measure the value of the anode current for certain values of the anode voltage (not B +) and the negative voltage of the control grid). If these values are greater than shown in the diagram, then the electron tube is in a new state. For example for measuring point A for anode voltage Vp = 60V and control grid voltage Ec = 0, the anode current Ip should be greater than 2.5mA, and so on.

For electron tube 310, the anode current and screen grid current should be measured for the three measuring points shown in the red box, the first being Vp = 135V, Vsg = 135V and Vcg = -3V. If the values of the measured currents are higher, then the electronic tube is in a new state.


You can interpret the obtained results to customers in percentages, so for point A if 3mA is measured, then 3 / 2.5 = 1.2 or 120%
Also using points A and B the values for mi, gm and rp can be calculated. I hope I helped a little.

 

[jdurango]

Honestly, all this is over my head (hence sending out to a tech). I'm just trying to figure out if these tubes are "good" or not so I can sell them, and preferably pass on some usable data to the buyer (ie. a "Hickok number"). It sounds like I might have to find someone else who is better with tube gear specifically? This guy is excellent with audio circuitry in general, but mostly works on newer stuff.