Valve help - stuck with reading

[Tim F]

I’m a bit stuck trying to understand how closely a bunch of valves I got as singles are. I'd like to create a matched pair. Can you help me translate the ratings given? All tubes are the same type a 12A

valve 1
TESTED gm1600

valve 2
Tested on a TV 7
Results = 72

valve 3
Tested on a Hickok 6000A :
Nominal New = 7800
Min = 4680
Results = 9200

valve 4
Tested on TV-7/B. The tubes test very strong with a reading of 75. Minimum is 42.

Hope this makes sense!
Thanks, Tim

[Firebottle]

Not a lot!

If you have one at 72 and another at 75 that's good. However have they been tested at the same conditions?

One says tested on TV 7, the other TV-7/B, without knowing what these are it's difficult to be sure.

Is valve 1 gm=1600? Gm values are usually small. Looking at the data sheet the typical gm = 1.65.

[Tim F]

All valves are 12A type. I don’t know any more than that I’m afraid!

[IslandPink]

The Gm is just being quoted in Microsieverts rather than millisieverts, so the value is 1000 times larger.
Aka Micromhos, see for example the RCA sheet for the 112A ( = 12A )
https://frank.pocnet.net/sheets/021/1/112A.pdf
If they have been tested the same way, the figures sound fine to be used as a pair.

[Blackdog]

If you bought them with those numbers, they are totally useless. You have no way of knowing the conditions, calibrations of the testers.

[IslandPink]

They're not useless. I am assuming this is a DIY project, with 12A's ( ! )
Get some sort of circuit set up, with a B+, anode load, cathode resistor and bias. Get some voltage readings and compare current for that Va, and Vg to the datasheet. If it's above about 85% of the datasheet numbers you can use. Select the closest two as a pair.

[Blackdog]

You misunderstand. The numbers are useless for matching. They weren't tested on the same machine.
Your idea of setting up a circuit is a good one. If you want to match that's the best way.