Download HICKOK B TRANSCONDUCTANCE TUBE TESTER service manual & repair info for electronics experts. Daniel Schoo produced a classic document on calibrating a Hickok B/C tube tester which was published in on AudioXpress. Hickok B/C Mutual Conductance Tube Tester – Checkout and Calibration. Version Use this procedure to test and calibrate the Hickok Model C mutual .
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The method given above is directly based on the definition of transconductance.
Get the item you ordered or get your money back. The control grid voltage, both AC signal and DC bias components, feed to hjckok control grid through 2 resistors which are normally shorted out by P5 and P6.
If you are going to use Method 2 to adjust manuzl 5Y3 power supply symmetry see the next sectionmake sure that range C is as close to zero as possible. If you are only interested in checking the calibration, this section can be omitted. Be very careful unsoldering the wires from the terminals of mxnual transformer, as the terminal itself may not be very secure physically. Connect one lead of an accurate low voltage AC voltmeter hikok the lower bottom end of R12 50 ohm and the other lead to the top end of R13 ohm.
Make sure that the tester is in its usual orientation upand the meter properly zeroed before checking this. Since the grid bias and screen grid supply is the same and is unregulated, if the DUT has a screen grid that pulls much current, the grid bias voltage is almost sure to increase when P4 is pressed.
Use a jumper wire to connect the lower bottom end ,anual R12 to the junction of R13 and R9. Assuming that the values of the remaining resistors are correct, then the output voltages should be correctly calibrated as well. It acts as an integrator.
If you use test leads for this, be aware that the resistor may get fairly hot. However, if they are shorted it should be detected on the shorts testing. It still has some interesting and possibly significant ramifications.
What this gas circuit attempts to measure is actually the total grid current from any and all causes. So, if the tube has adequate emission, it is only necessary to apply a relatively small ihckok to get the rated current. Most tube testers do not use excessively high voltages and the obvious reason is simply that there is no good reason to do so or to justify the extra expense that would be involved.
Put a much larger value potentiometer across the combination of fixed resistor and replacement meter, say 50 K.
I am now happily retired and so finally have some time to play with things like tube testers. You now have the situation where half the It would also be relatively manuap to add a digital panel meter to routinely monitor the plate or screen grid voltages or to add a more accurate digital DC voltmeter to replace or parallel the built-in analog control grid bias voltage meter.
Accurate Calibration Of The Hickok B And Hickok C Tube Tester
It just has to be able to display V peak voltage at Hz. This is the easiest and probably the best approach. Or, maybe they just read it wrong! As a concrete example, consider an experiment measuring the transconductance of a 6L6GB tube mankal measured on a Hickok B mine, actually, but long before the modifications and before even very accurate calibrationwhere the transconductance measured about Micromho in the C range and Micromho on the D range, a difference of about 5.
Note that Rload includes everything in the loop except the calibration resistor including the equivalent resistances of the power supply and the sensing circuitry and R8. All the above are average DC values for a half wave pulsating DC waveform.
Accurate Calibration Of The Hickok 539B And Hickok 539C Tube Tester
Read more manuzl the condition. You could also think of this as a bridge circuit with the other half being the two separate volt windings, each in series with half of the 83 rectifier tube. I think it is pretty well accepted that most tube Hickok tube testers do a pretty good job at this, irregardless of exactly ,anual the plate voltage they actually use in order to do it.
The voltage on C3 depends on the amount of charge on the plates of C3, which is equal to the current at each instant times the amount of time that it is at that value. The B meter should also read exactly Re-adjust the voltage source to keep It will give better theoretical accuracy, but requires a lot of changes.
Hickok B Tube Tester Instruction Manual Includes 11″ X 17″ foldout schematic and general, obsolete, and foreign tube data – pages total. Add to watch list Remove from watch list.
In fact, this method could be used to accurately calibrate just about any tester, but it would be a bit cumbersome and inconvenient. If you look at the 5Y3 characteristic curves in a tube book, you will see they are not straight lines as in a resistor but, well, curves. Method 1 not recommended, less accurate.
Also, the resistance of the 53b9 insulators commonly used in tubes varies with the voltage applied, and becomes lower at the high voltages that some testers use, thus it is possible for some shorts testers to produce shorts where none existed before.
See Figure 3 Line Adjust Circuit. Engineering design is always a set of trade-offs, and at the time, this would have been considered good engineering practice.
Thus changes or inaccuracies in the shunt have little effect.
Hickok B Tube Tester Instruction Manual & Tube Data | eBay
A close second is to examine the tube dynamic traces. The definition of transconductance assumes that pure DC is applied to the plate and the various grids of the DUT with a small AC signal superimposed on the DC bias voltage of the control grid. Putting the pass transistor within the bridge rectifier insures that each half cycle is treated the same This 539 important for the Hickok transconductance measuring circuitry and allows a DC device, a bipolar junction transistor, to be used in a AC application.
Remove the scope when done. The ones given here are the simplest and the only ones that I recommend. There are no adjustments that allow for correcting the gain of any of the ranges.
Manuql C3 were not used, the physical inertia of the meter movement would perform the same function. Okay, I made that last part up, but you get the idea, I hope.
You may find it convenient to set this for about This item will be shipped through the Global Shipping Program and includes international tracking. The one possible exception is that the AC voltmeter used nanual checking the grid bias voltage must be at least as accurate as the overall tester accuracy desired, but this should not be a major hurdle.
Second, any asymmetry in the bias voltage peaks will have the same effect on the transconductance sensing circuit as a transconductance caused change in the plate current.
539bb errors in the grid voltage signal is multiplied by the transconductance of the tube before it gets to the sensing circuitry.