Correct Parameters to Enter for a Quick Test KT120

[Rocko]

Hello,

Well I have compared the examples I have found online to the data sheets and have figured out what goes where for some tubes. 12xx7 testing is a success! 

However, I was wondering if someone could direct me to a walk through for a tube such as testing a KT120.  I understand that the Utracer 3+ cannot test it at max operating values but reading on Ronald's page he managed to test one for a potential customer to generate accurate results.  (The customer bought a kit because of it).  

He did not list his test parameters and well when I look at the spec sheet I get a little freaked out that I may be entering the wrong info.

I am using an external power supply for the heater so I think I can leave the heater settings in Utracer at whatever, but I will use 6.3V at 1.7 - 1.95 amps on the external heater power supply?

Also, the pinnout from the Tube Socket to the Utracer 3+ is:

1- nothing yeah?

2 & 7 - H, is this heater wires?

3 - P, is this Plate so a wire from S or A?

4 & 5 - G1 &G2 so 2 a wire from G to both of these?

6 - No pin yeah!

8 - K,G3 A wire from C?

Again, any help would be appreciated with this.  I really hope you are not tired of me already.  Thanks in advance!

Paul

[Boban]

Hi,

KT88 and KT90 and KT120 are interchangeable electrically and have the same pinouts. This is how I connected KT88.

1: n/a

2: Heater1

3: Anode

4: Screen

5: Grid

6: n/a

7: Heater2

8: Cathode

Hope this helps.

Bob

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[Martin Manning]

Here is a KT120 data sheet: https://www.tungsol.com/specs/kt120-tung-sol-specs-curves.pdf

On the second page there is a point for a class A amplifier at 400 Va, 225 Vg2, -14 Vg1, where Ia = 135-165 mA, Ig2 = <=14 mA, gm = 12.5 S, and ra = 3000.

The standard uT3+ can test at that point, but for the Quick Test Va input you will have to set say 390V and +/- 2.5% variation to stay under the 400V limit.

On page 5 there are anode curves for Vg2 = 225, 0-500 Va, and -25 to 0V Vg1. Since Ia tops out at something over 400 mA at Va = 400 and Vg1 = 0, you cannot reproduce the entire set. You could get most or all of the Vg1 = -10V curve, if you switch the software compliance limit off.

I am running my uT3+ in high-current configuration where Ia and Is current limits are increased to 600 mA, which is easily enough to trace the whole set of curves. I recommend modifying yours (easily done, as described on the uTracer Lab Notebook pages here: https://www.dos4ever.com/uTracerNotebook/Notebook.html#Current2) to that configuration if you want to test large power tubes. 

[Big Josh]

You can use the same socket wiring for those, and EL34, 6V6, 6L6, etc.

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[Martin Manning]

Except for EL34, where you must tie the suppressor grid (pin 1) to the cathode (pin 8). On the other beam tubes mentioned this connection is made internally.

[Big Josh]

RIght, but if you already have a socket wired for EL34, then those tubes will work on it.

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[Rocko]

Thanks guys for all the replies.  I did the 600V upgrade and still have to test a KT120 yet but I made my 9 pin and 8 pin sockets and wow I am testing!  Yeehaaaaa.  I am going to go through the entire calibration again but with the separate power supply wow my tubes are better than I thought!   A pair of new Gold Lion 12AU7 are just garbage, it is like no wonder after putting them in my amp I pulled them within minutes.  

I am saving each configuration for each new tube I enter but is there a data base of tube files that is anywhere to download?  It is a great learning experience creating each one but after the first few it is just wow.  I keep thinking about my glass of wine and then i start to make mistakes, etc etc.

I am going to start on the tracing next and see if I can figure out that so it doesn't take me 20 minutes to make sure I have everything entered correctly.

Thanks again, any more hints or tricks please pass them along.  I am thinking a 1000V model may be in my future, my soldering is better than I thought.  

Has anybody ever tested like a QB5/1750 tube with success?

Rocko

[theold...@gmail.com]

My goto site for tube data is Frank’s Electron tube Pages:

 

http://www.tubedata.org/

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