I have a Heath IT-21 tube tester. Very reliable thus far. The 6U5 "Eye Tube" is not on the roll chart but is on my "Supplement Test Data Sheet" for the IT-21. The 6U5 has a "Type 2", "Filament 6.3", "Plate 34" and then the associated "Top" and "Bottom" switch positions on the tester. On these settings the tube tests good but if I use the two other listings under the 6U5, "Eye CL" or "Eye OP", (big difference being the "Plate" setting on the tester is set to "0") the tube tests bad. Which criteria do I use to test this tube properly? Thanks!

Hi Johnny,
Usually the way tube testers test these is that the first test is of the triode section. This is the test yours passes. They usually do.
The eye open and eye closed tests are tests of the brightness of the tube, the real test, because these usually fail due to weak brightness.
In these tests the reading on the meter is not used. The test is to look at the eye. If it is bright enough to use, it is good, if not it is bad.

Best Regards,

Bill Grimm

:Hi Johnny,
: Usually the way tube testers test these is that the first test is of the triode section. This is the test yours passes. They usually do.
: The eye open and eye closed tests are tests of the brightness of the tube, the real test, because these usually fail due to weak brightness.
: In these tests the reading on the meter is not used. The test is to look at the eye. If it is bright enough to use, it is good, if not it is bad.
:
:Best Regards,
:
:Bill Grimm
:
:Thanks Bill! So I should allow the tube to warm up on the tester and if there is no glow at all the tube is bad?

:Hi Johnny,
: Usually the way tube testers test these is that the first test is of the triode section. This is the test yours passes. They usually do.
: The eye open and eye closed tests are tests of the brightness of the tube, the real test, because these usually fail due to weak brightness.
: In these tests the reading on the meter is not used. The test is to look at the eye. If it is bright enough to use, it is good, if not it is bad.
:
:Best Regards,
:
:Bill Grimm
:
:Hi again. I retested the tube with the same results and definitely no glow. I tested the rest of the tubes and they are good with the exception of the 6A8. Wouldn't ya know...I have a couple hundred tubes and no 6A8. I took a chance and powered the radio up and dial lamps lit, static from speaker, (no antenna connected) but still no glow from eye tube. Does this tube only glow when the radio is receiving a strong station? What is this tube for?

::Hi Johnny,
:: Usually the way tube testers test these is that the first test is of the triode section. This is the test yours passes. They usually do.
:: The eye open and eye closed tests are tests of the brightness of the tube, the real test, because these usually fail due to weak brightness.
:: In these tests the reading on the meter is not used. The test is to look at the eye. If it is bright enough to use, it is good, if not it is bad.
::
::Best Regards,
::
::Bill Grimm
::
::Hi again. I retested the tube with the same results and definitely no glow. I tested the rest of the tubes and they are good with the exception of the 6A8. Wouldn't ya know...I have a couple hundred tubes and no 6A8. I took a chance and powered the radio up and dial lamps lit, static from speaker, (no antenna connected) but still no glow from eye tube. Does this tube only glow when the radio is receiving a strong station? What is this tube for?

Johnny:
This tube is like a vaccum tube Voltmeter. It is connected across the AVC bus, which goes more negative when receiving a strong signal. The triode section of this tube amplifies the negative AVC Voltage and also inverts it so the plate becomes more positive. The phosper (how the **** do you spell it?) stays the same brightness, but there is an electrode that blocks the electrons for an angle of about 60 degrees, so there is a "wedge" of dimmer light on weak signals that closes as you tune to stronger stations. To repeat, your brightness is fixed, and does not change with signal strength. BTW, this system was used on early tape recorders as a recording level meter, so you might find one looking for an old tape machine.
Lewis

Hi Johnny

Eye tubes lose green long before a tube shows weak emission on a tester. An eye tube that doesn't show green has no effect on circuit operation. A radio will work without it.

You do need a 6A8 to operate your radio. In some caes a 6K8 will work in place of 6A8. Substitution books may show 6D8 but that one isn't very common.

Norm

:::Hi Johnny,
::: Usually the way tube testers test these is that the first test is of the triode section. This is the test yours passes. They usually do.
::: The eye open and eye closed tests are tests of the brightness of the tube, the real test, because these usually fail due to weak brightness.
::: In these tests the reading on the meter is not used. The test is to look at the eye. If it is bright enough to use, it is good, if not it is bad.
:::
:::Best Regards,
:::
:::Bill Grimm
:::
:::Hi again. I retested the tube with the same results and definitely no glow. I tested the rest of the tubes and they are good with the exception of the 6A8. Wouldn't ya know...I have a couple hundred tubes and no 6A8. I took a chance and powered the radio up and dial lamps lit, static from speaker, (no antenna connected) but still no glow from eye tube. Does this tube only glow when the radio is receiving a strong station? What is this tube for?
:
:
:
:Johnny:
:This tube is like a vaccum tube Voltmeter. It is connected across the AVC bus, which goes more negative when receiving a strong signal. The triode section of this tube amplifies the negative AVC Voltage and also inverts it so the plate becomes more positive. The phosper (how the **** do you spell it?) stays the same brightness, but there is an electrode that blocks the electrons for an angle of about 60 degrees, so there is a "wedge" of dimmer light on weak signals that closes as you tune to stronger stations. To repeat, your brightness is fixed, and does not change with signal strength. BTW, this system was used on early tape recorders as a recording level meter, so you might find one looking for an old tape machine.
:Lewis

:Hi Johnny
:
: Eye tubes lose green long before a tube shows weak emission on a tester. An eye tube that doesn't show green has no effect on circuit operation. A radio will work without it.
:
: You do need a 6A8 to operate your radio. In some caes a 6K8 will work in place of 6A8. Substitution books may show 6D8 but that one isn't very common.
:
:Norm
:
:
:
::::Hi Johnny,
:::: Usually the way tube testers test these is that the first test is of the triode section. This is the test yours passes. They usually do.
:::: The eye open and eye closed tests are tests of the brightness of the tube, the real test, because these usually fail due to weak brightness.
:::: In these tests the reading on the meter is not used. The test is to look at the eye. If it is bright enough to use, it is good, if not it is bad.
::::
::::Best Regards,
::::
::::Bill Grimm
::::
::::Hi again. I retested the tube with the same results and definitely no glow. I tested the rest of the tubes and they are good with the exception of the 6A8. Wouldn't ya know...I have a couple hundred tubes and no 6A8. I took a chance and powered the radio up and dial lamps lit, static from speaker, (no antenna connected) but still no glow from eye tube. Does this tube only glow when the radio is receiving a strong station? What is this tube for?
::
::
::
::Johnny:
::This tube is like a vaccum tube Voltmeter. It is connected across the AVC bus, which goes more negative when receiving a strong signal. The triode section of this tube amplifies the negative AVC Voltage and also inverts it so the plate becomes more positive. The phosper (how the **** do you spell it?) stays the same brightness, but there is an electrode that blocks the electrons for an angle of about 60 degrees, so there is a "wedge" of dimmer light on weak signals that closes as you tune to stronger stations. To repeat, your brightness is fixed, and does not change with signal strength. BTW, this system was used on early tape recorders as a recording level meter, so you might find one looking for an old tape machine.
::Lewis
:
:Thanks folks! I think I'm gonna put this one on ebay. I don't really want or need the chassis and I would hate to part out a perfectly good radio. It has the motor tuning and eye tube so I believe someone would be interested. I'd really like to swap it for a chassis for my Sparton. There was one on ebay recently but I was outbid in the last 60 seconds.

:Hi Johnny
:
: Eye tubes lose green long before a tube shows weak emission on a tester. An eye tube that doesn't show green has no effect on circuit operation. A radio will work without it.
:
: You do need a 6A8 to operate your radio. In some caes a 6K8 will work in place of 6A8. Substitution books may show 6D8 but that one isn't very common.
:
:Norm
:
:
:
::::Hi Johnny,
:::: Usually the way tube testers test these is that the first test is of the triode section. This is the test yours passes. They usually do.
:::: The eye open and eye closed tests are tests of the brightness of the tube, the real test, because these usually fail due to weak brightness.
:::: In these tests the reading on the meter is not used. The test is to look at the eye. If it is bright enough to use, it is good, if not it is bad.
::::
::::Best Regards,
::::
::::Bill Grimm
::::
::::Hi again. I retested the tube with the same results and definitely no glow. I tested the rest of the tubes and they are good with the exception of the 6A8. Wouldn't ya know...I have a couple hundred tubes and no 6A8. I took a chance and powered the radio up and dial lamps lit, static from speaker, (no antenna connected) but still no glow from eye tube. Does this tube only glow when the radio is receiving a strong station? What is this tube for?
::
::
::
::Johnny:
::This tube is like a vaccum tube Voltmeter. It is connected across the AVC bus, which goes more negative when receiving a strong signal. The triode section of this tube amplifies the negative AVC Voltage and also inverts it so the plate becomes more positive. The phosper (how the **** do you spell it?) stays the same brightness, but there is an electrode that blocks the electrons for an angle of about 60 degrees, so there is a "wedge" of dimmer light on weak signals that closes as you tune to stronger stations. To repeat, your brightness is fixed, and does not change with signal strength. BTW, this system was used on early tape recorders as a recording level meter, so you might find one looking for an old tape machine.
::Lewis

:
:
:
:
::::Hi Johnny,
:::: Usually the way tube testers test these is that the first test is of the triode section. This is the test yours passes. They usually do.
:::: The eye open and eye closed tests are tests of the brightness of the tube, the real test, because these usually fail due to weak brightness.
:::: In these tests the reading on the meter is not used. The test is to look at the eye. If it is bright enough to use, it is good, if not it is bad.
::::
::::Best Regards,
::::
::::Bill Grimm
::::
::::Hi again. I retested the tube with the same results and definitely no glow. I tested the rest of the tubes and they are good with the exception of the 6A8. Wouldn't ya know...I have a couple hundred tubes and no 6A8. I took a chance and powered the radio up and dial lamps lit, static from speaker, (no antenna connected) but still no glow from eye tube. Does this tube only glow when the radio is receiving a strong station? What is this tube for?
::
::
::
::Johnny:
::This tube is like a vaccum tube Voltmeter. It is connected across the AVC bus, which goes more negative when receiving a strong signal. The triode section of this tube amplifies the negative AVC Voltage and also inverts it so the plate becomes more positive. The phosper (how the **** do you spell it?) stays the same brightness, but there is an electrode that blocks the electrons for an angle of about 60 degrees, so there is a "wedge" of dimmer light on weak signals that closes as you tune to stronger stations. To repeat, your brightness is fixed, and does not change with signal strength. BTW, this system was used on early tape recorders as a recording level meter, so you might find one looking for an old tape machine.
::Lewis

Johnny:

New old stock 6u5 aka 6G5 magic eye tubes are often on auction on E-Bay or available from several internet tube sites. These tubes tend to be pricey, in the $40-50 range before shipping. With a special adaptor you can use a 1629 eye tube or a Russian 6E5s. An American 6E5 will serve as a substite for a 6u5, without the need for an adaptor socket, but its "wedge" will close more than the 6u5 does when a strong signal is tuned in.

One place for a ready-made 1629 to 6U5 adapter is:

http://www.dialcover.com/tubes.html

The adapter is down about half way of the page. You can purchase the adapter only or the adapter with 1629 tube. The adapter adds 1 3/4 inches to the length of the tube and socket, so it may not fit in some cases.

Radiodoc
*****************

::
::
::
::
:::::Hi Johnny,
::::: Usually the way tube testers test these is that the first test is of the triode section. This is the test yours passes. They usually do.
::::: The eye open and eye closed tests are tests of the brightness of the tube, the real test, because these usually fail due to weak brightness.
::::: In these tests the reading on the meter is not used. The test is to look at the eye. If it is bright enough to use, it is good, if not it is bad.
:::::
:::::Best Regards,
:::::
:::::Bill Grimm
:::::
:::::Hi again. I retested the tube with the same results and definitely no glow. I tested the rest of the tubes and they are good with the exception of the 6A8. Wouldn't ya know...I have a couple hundred tubes and no 6A8. I took a chance and powered the radio up and dial lamps lit, static from speaker, (no antenna connected) but still no glow from eye tube. Does this tube only glow when the radio is receiving a strong station? What is this tube for?
:::
:::
:::
:::Johnny:
:::This tube is like a vaccum tube Voltmeter. It is connected across the AVC bus, which goes more negative when receiving a strong signal. The triode section of this tube amplifies the negative AVC Voltage and also inverts it so the plate becomes more positive. The phosper (how the **** do you spell it?) stays the same brightness, but there is an electrode that blocks the electrons for an angle of about 60 degrees, so there is a "wedge" of dimmer light on weak signals that closes as you tune to stronger stations. To repeat, your brightness is fixed, and does not change with signal strength. BTW, this system was used on early tape recorders as a recording level meter, so you might find one looking for an old tape machine.
:::Lewis
:
:Johnny:
:
:New old stock 6u5 aka 6G5 magic eye tubes are often on auction on E-Bay or available from several internet tube sites. These tubes tend to be pricey, in the $40-50 range before shipping. With a special adaptor you can use a 1629 eye tube or a Russian 6E5s. An American 6E5 will serve as a substite for a 6u5, without the need for an adaptor socket, but its "wedge" will close more than the 6u5 does when a strong signal is tuned in.

Johnny, just to recap. Your tester tests for emissions of the triode and on the "closed" "open"
test it is visual observation of the tube not the meter. The top circular element of the tube should glow green and have a wedge of about 30 degrees that appears darker in the "open" possition. In the "closed" position test the wedge should close to zero degrees. Actually you will still see a line. The way this is used in a radio is to indicate when you are receiving the maximum signal for a frequency. As you tune toward the frequency peak the eye will start to close, at peak will be closed and as you pass peak will start to open. As Norm said the tube is not necessary for the operation of the set but was a cool sales gimmick. You can use your ears to do the same thing. PL

:One place for a ready-made 1629 to 6U5 adapter is:
:
:http://www.dialcover.com/tubes.html
:
:The adapter is down about half way of the page. You can purchase the adapter only or the adapter with 1629 tube. The adapter adds 1 3/4 inches to the length of the tube and socket, so it may not fit in some cases.
:
:Radiodoc
:*****************
:
:
:::
:::
:::
:::
::::::Hi Johnny,
:::::: Usually the way tube testers test these is that the first test is of the triode section. This is the test yours passes. They usually do.
:::::: The eye open and eye closed tests are tests of the brightness of the tube, the real test, because these usually fail due to weak brightness.
:::::: In these tests the reading on the meter is not used. The test is to look at the eye. If it is bright enough to use, it is good, if not it is bad.
::::::
::::::Best Regards,
::::::
::::::Bill Grimm
::::::
::::::Hi again. I retested the tube with the same results and definitely no glow. I tested the rest of the tubes and they are good with the exception of the 6A8. Wouldn't ya know...I have a couple hundred tubes and no 6A8. I took a chance and powered the radio up and dial lamps lit, static from speaker, (no antenna connected) but still no glow from eye tube. Does this tube only glow when the radio is receiving a strong station? What is this tube for?
::::
::::
::::
::::Johnny:
::::This tube is like a vaccum tube Voltmeter. It is connected across the AVC bus, which goes more negative when receiving a strong signal. The triode section of this tube amplifies the negative AVC Voltage and also inverts it so the plate becomes more positive. The phosper (how the **** do you spell it?) stays the same brightness, but there is an electrode that blocks the electrons for an angle of about 60 degrees, so there is a "wedge" of dimmer light on weak signals that closes as you tune to stronger stations. To repeat, your brightness is fixed, and does not change with signal strength. BTW, this system was used on early tape recorders as a recording level meter, so you might find one looking for an old tape machine.
::::Lewis
::
::Johnny:
::
::New old stock 6u5 aka 6G5 magic eye tubes are often on auction on E-Bay or available from several internet tube sites. These tubes tend to be pricey, in the $40-50 range before shipping. With a special adaptor you can use a 1629 eye tube or a Russian 6E5s. An American 6E5 will serve as a substite for a 6u5, without the need for an adaptor socket, but its "wedge" will close more than the 6u5 does when a strong signal is tuned in.

:Why are we talking about an adapter? I was just trying to clarify the test procedure. I was able to get the radio configured enough to power it up and there is no green glow coming from the eye tube at all. While in the radio or on the tester. I'm not really gonna go any further with this chassis. I've decided to throw it on ebay and see if someone needs it more then I do. I think I've been able to identify the cabinet. Evidently it was used in schools and was actually hooked up to speakers in each classroom. All of the switches (40 of them) on the front of the cabinet were used to switch from one classroom to another. "Johnny! Please report to the principals office...IMMEDIATELY!!! But why the phonograph? I guess to play music during Xmas or something.
:
: Johnny, just to recap. Your tester tests for emissions of the triode and on the "closed" "open"
:test it is visual observation of the tube not the meter. The top circular element of the tube should glow green and have a wedge of about 30 degrees that appears darker in the "open" possition. In the "closed" position test the wedge should close to zero degrees. Actually you will still see a line. The way this is used in a radio is to indicate when you are receiving the maximum signal for a frequency. As you tune toward the frequency peak the eye will start to close, at peak will be closed and as you pass peak will start to open. As Norm said the tube is not necessary for the operation of the set but was a cool sales gimmick. You can use your ears to do the same thing. PL
:
:
:
::One place for a ready-made 1629 to 6U5 adapter is:
::
::http://www.dialcover.com/tubes.html
::
::The adapter is down about half way of the page. You can purchase the adapter only or the adapter with 1629 tube. The adapter adds 1 3/4 inches to the length of the tube and socket, so it may not fit in some cases.
::
::Radiodoc
::*****************
::
::
::::
::::
::::
::::
:::::::Hi Johnny,
::::::: Usually the way tube testers test these is that the first test is of the triode section. This is the test yours passes. They usually do.
::::::: The eye open and eye closed tests are tests of the brightness of the tube, the real test, because these usually fail due to weak brightness.
::::::: In these tests the reading on the meter is not used. The test is to look at the eye. If it is bright enough to use, it is good, if not it is bad.
:::::::
:::::::Best Regards,
:::::::
:::::::Bill Grimm
:::::::
:::::::Hi again. I retested the tube with the same results and definitely no glow. I tested the rest of the tubes and they are good with the exception of the 6A8. Wouldn't ya know...I have a couple hundred tubes and no 6A8. I took a chance and powered the radio up and dial lamps lit, static from speaker, (no antenna connected) but still no glow from eye tube. Does this tube only glow when the radio is receiving a strong station? What is this tube for?
:::::
:::::
:::::
:::::Johnny:
:::::This tube is like a vaccum tube Voltmeter. It is connected across the AVC bus, which goes more negative when receiving a strong signal. The triode section of this tube amplifies the negative AVC Voltage and also inverts it so the plate becomes more positive. The phosper (how the **** do you spell it?) stays the same brightness, but there is an electrode that blocks the electrons for an angle of about 60 degrees, so there is a "wedge" of dimmer light on weak signals that closes as you tune to stronger stations. To repeat, your brightness is fixed, and does not change with signal strength. BTW, this system was used on early tape recorders as a recording level meter, so you might find one looking for an old tape machine.
:::::Lewis
:::
:::Johnny:
:::
:::New old stock 6u5 aka 6G5 magic eye tubes are often on auction on E-Bay or available from several internet tube sites. These tubes tend to be pricey, in the $40-50 range before shipping. With a special adaptor you can use a 1629 eye tube or a Russian 6E5s. An American 6E5 will serve as a substite for a 6u5, without the need for an adaptor socket, but its "wedge" will close more than the 6u5 does when a strong signal is tuned in.