i have 500-1000 old tubes.the marking have worn off most.how do i tell what is what?

:i have 500-1000 old tubes.the marking have worn off most.how do i tell what is what?
hi you can get them cold maybe put them in the freezer for awhile then breath on them to fog them up and usually the number will show there are probably other ways but i don't know of any . butch

If you have some that the freezer won't reveal, there are many other ways that are a little less accurate. Trying them in the freezer is best. What you can do, though, if no number is available, is compare them with tubes you do know. For instance, if you had a 4 pin triode wired in standard form (there is a popular form, and there is a second form that is much less popular), you could look at the filament. Triangular and lighting properly at 2.0 volts would likely be a 26 or . Double triangle and 2.5 volts would likely be either a 45 or a 2A3. Double triangle and 5.0 volts would likely be an 01A or 71A. On and on....

Simple ones are like....7 pin miniature, rather tall, 50 volt filament, beam power pentode construction--wired one way would be a 50B5, and a slightly different way would be 50C5. Consult a tube manual or your memory if you are familiar with these tubes. There were only a few types produced, so determining the type is easy. Keep in mind, too, that the above tubes were also produced with 35 and 25 volt filaments (35C5, 25C5, etc.).

In the case of power pentodes, like those listed above, you will find in the AC tube category some regular pentode output tubes--the 6F6 and 6K6--the former has a taller plate than the latter. Then you will find the beam-power tubes, which have a plate-like third grid construction. Those would be the 6V6, which is often similar in looks to the 6K6, though I have seen a square plate on these. Then there is the 6L6, which has a much taller plate than the 6V6. These are all wired the same, but some handle more power and some do not. Some are beam power and some are not. Knowing filament amperage draw and having an ammeter handy does help a little.

There are some things that cannot easily be told by looking at a tube. The 6AU6 is a sharp cut-off pentode. It has an evenly spaced control grid that allows the tube to completely cut off all function with the appropriate voltage. A similar tube is the 6BA6, but this tube is a remote cut-off tube, and has a control grid with different spacing. Each tube has a definite purpose. They both look almost identical and are wired in the same manner. Luckily I have found that they both usually work about the same in many circuits. There is a definite purpose for each, though. Also, you may run into variations of these such as the 12BA6 (12 volt filament and very common), and the 4AU6 (4 volt filament and somewhat uncommon), and others.

When assuming that one tube is like another, other than internal grid construction and power handling capability, be on the lookout for extra connections in one tube that are not there in another. If such a tube is used in certain circuits not designed for it, it may ruin th equipment. Power handling capability is a big thing to be aware of. A radio may have originally taken a #42 or 6F6 tube (both equivilant, but different bases). Replacing such a tube with a #41 or 6K6 tube (also equivilant to eachother, and each is wired like its similar tube above) will put a lot of stress on the latter tube, as it is not designed for the power that the 42/6F6 handles. It is likely that your plates and screen grids will glow red.

Thomas

:If you have some that the freezer won't reveal, there are many other ways that are a little less accurate. Trying them in the freezer is best. What you can do, though, if no number is available, is compare them with tubes you do know. For instance, if you had a 4 pin triode wired in standard form (there is a popular form, and there is a second form that is much less popular), you could look at the filament. Triangular and lighting properly at 2.0 volts would likely be a 26 or . Double triangle and 2.5 volts would likely be either a 45 or a 2A3. Double triangle and 5.0 volts would likely be an 01A or 71A. On and on....
:
:Simple ones are like....7 pin miniature, rather tall, 50 volt filament, beam power pentode construction--wired one way would be a 50B5, and a slightly different way would be 50C5. Consult a tube manual or your memory if you are familiar with these tubes. There were only a few types produced, so determining the type is easy. Keep in mind, too, that the above tubes were also produced with 35 and 25 volt filaments (35C5, 25C5, etc.).
:
:In the case of power pentodes, like those listed above, you will find in the AC tube category some regular pentode output tubes--the 6F6 and 6K6--the former has a taller plate than the latter. Then you will find the beam-power tubes, which have a plate-like third grid construction. Those would be the 6V6, which is often similar in looks to the 6K6, though I have seen a square plate on these. Then there is the 6L6, which has a much taller plate than the 6V6. These are all wired the same, but some handle more power and some do not. Some are beam power and some are not. Knowing filament amperage draw and having an ammeter handy does help a little.
:
:There are some things that cannot easily be told by looking at a tube. The 6AU6 is a sharp cut-off pentode. It has an evenly spaced control grid that allows the tube to completely cut off all function with the appropriate voltage. A similar tube is the 6BA6, but this tube is a remote cut-off tube, and has a control grid with different spacing. Each tube has a definite purpose. They both look almost identical and are wired in the same manner. Luckily I have found that they both usually work about the same in many circuits. There is a definite purpose for each, though. Also, you may run into variations of these such as the 12BA6 (12 volt filament and very common), and the 4AU6 (4 volt filament and somewhat uncommon), and others.
:
:When assuming that one tube is like another, other than internal grid construction and power handling capability, be on the lookout for extra connections in one tube that are not there in another. If such a tube is used in certain circuits not designed for it, it may ruin th equipment. Power handling capability is a big thing to be aware of. A radio may have originally taken a #42 or 6F6 tube (both equivilant, but different bases). Replacing such a tube with a #41 or 6K6 tube (also equivilant to eachother, and each is wired like its similar tube above) will put a lot of stress on the latter tube, as it is not designed for the power that the 42/6F6 handles. It is likely that your plates and screen grids will glow red.
:
:Thomas

:i have 500-1000 old tubes.the marking have worn off most.how do i tell what is what?

Blacklite works good

::i have 500-1000 old tubes.the marking have worn off most.how do i tell what is what?
:
:

Blacklite works good

hi i never thought of a uv lamp i'll have to try it i have one around here somewhere will it show up numbers better than fogging the tube? butch

:::i have 500-1000 old tubes.the marking have worn off most.how do i tell what is what?
::
::
:
: Blacklite works good
:
:hi i never thought of a uv lamp i'll have to try it i have one around here somewhere will it show up numbers better than fogging the tube? butch.

Yes..give it a try..Randy