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Tubes to test

A project log for Testing vacuum tubes without a tester

Short, leakage and emission testing with just basic tools

QuinnQuinn 07/04/2022 at 20:120 Comments

I have a set of tubes to test for an amplifier.  I'll go through them.

5V4G

First is the rectifier/dual diode used in power supply.

Pinout:

1ANC
2BHeater 1
3C(Missing)
4DPlate 1
5E(Missing)
6FPlate 2
7G(Missing)
8HHeater 2 / Cathode

The letters correspond to how the tester refers to the pins.

The tube data lists these values:

Element 1Element 2
Type33
Filament55
Plate2525
Top (Plate)FD
Bottom
(Cathode/Filament)
(H)(H)

Not listed in there, but all other switches are middle, which is connected to the other side of the filament voltage, "positive".

Type 3 means, a B+ of 30v, plate R of 0 ohm and meter R of 1500.

6SN7 *2

A dual triode, used in preamp and phase inverter.

Pinout:

1AGrid 2
2BPlate 2
3CCathode 2
4DGrid 1
5EPlate 1
6FCathode 1
7GHeater 1
8HHeater 2

The tube data lists these values:

Element 1Element 2
Type22
Filament6.36.3
Plate2626
Top (Plate)DEAB
Bottom 
(Cathode/Filament)
(F)(G)C(G)

Not listed in there, but all other switches are middle, which is connected to the other side of the filament voltage, "positive".  It's puzzling that F is bolded, but not C.  Seems like F shouldn't be.

Type 2 means, a B+ of 30v, plate R of 820 ohm and meter R of 360

5881 (6L6?) *2

A beam pentode used as output drivers.

The catch here is that with the tubes I have, no markings are visible.  The version w3 schematics these are marked as 5881, but the tube shape doesn't seem right, and doesn't match the pictures.  Other sources suggest they could be 6L6.  So I'll look up values for both and we can see what it looks like.

Pinout:

1AShell / NC
2BHeater 
3CPlate
4DGrid 2 (screen)
5EGrid 1
6F(Missing)
7GHeater 
8HCathode / Grid 3

Both 5881 and 6L6 share the same pinout, so that's a good start.

The tube data lists these values:

6L65881
Type33
Filament6.36.3
Plate2720
Top (Plate)CDECDE
Bottom 
(Cathode/Filament)
(G)H(B)H

Not listed in there, but all other switches are middle, which is connected to the other side of the filament voltage, "positive".  It's interesting that the only pinout difference here is the "polarity" of the filament, which wouldn't seem to matter.

Type 3 means, a B+ of 30v, plate R of 0 ohm and meter R of 1500.

Reference 6DJ8 / ECC88

As we still have one missing value from the circuit, I'm going to use a reference tube that I have a lot of, in this case a set of Amperex 6DJ8/ECC88 's. While these are all used, my hope is that by testing a bunch, I can find a common value and build certainty with that 

This is a dual triode 

Pinout:

1APlate 1
2BGrid 1
3CCathode 1
4DHeater
5EHeater 
6FPlate 2
7GGrid 2
8HCathode 2
9JShield

The letters correspond to how the tester refers to the pins.

The tube data lists these values:

Element 1Element 2
Type22
Filament6.36.3
Plate2121
Top (Plate)ABFG
Bottom (Cathode/Filament) C(E)(E)H

Not listed in there, but all other switches are middle, which is connected to the other side of the filament voltage, "positive".  The bolding didn't make sense, so I updated here to be what I think it is 

Type 2 means, a B+ of 30v, plate R of 820 ohm and meter R of 360.

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