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Another tube tester question



 
 
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Old November 18th 04, 07:47 AM
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Default Another tube tester question

I was reading the other post about a tube tester. I need one also, but after
going through all the tube testers for sale on ebay.....I realized I have no
idea what to get. Some of them say they will check almost all TV tubes, but
does that also mean they will check Jukebox(radio) tubes as well? What does
mutual conductunce mean? Ive seen that on several of them. Some seem to have
only 4 or 5 holes to check tubes in, while others have anywhere between 10
and 25 or more holes for tubes.How do I know what to get that will check the
tubes in my 1953 Seeburg and any future jukeboxes I get? If any of you
experts out there can shed some light on what I and obviously some others
here need to get, I would really appreciate it. Id sure hate to buy one and
find it does not have testing sockets for the tubes I have. Thanks in
advance for however can help me out with this, because I know nothing about
tubes at this point..........Mickey


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  #2  
Old November 18th 04, 03:07 PM
Tenpin
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The first thing to consider is that no tube tester will exactly duplicate
all of the circuits any given tube type will encounter in actual use. When
tubes were plentiful ( and a lot cheaper than they are today ) the best
method for testing suspect tubes was by direct replacement with a known new
or good one. Most of the more common tube testers, especially the lower
priced ones are basically " Emission " testers and will give a very basic
test although it will not put the kind of load on the tube that it may
encounter in actual use. Rule of thumb for Emission Testers used to be that
if ( when properly set ) it indicated the tube was Bad, it most likely was
although it still may have had a little life in it depending on the way it
was used. Mutual Conductance Tube Testers ( more costly & more
sophisticated than an Emission Tester ) are able to better simulate average
real life operating conditions for a given tube type. Mutual Conductance
Tube Testers can give a more accurate condition of a tube and measure
parameters other than just the electron emission from the cathode to the
plate. A telltale sign that a tube tester is of the Mutual Conductance type
will have a scale on the meter calibrated in " Micromhos " ( not to be
confused with Micro ohms ). It would be best to make a list of the type of
tubes you may encounter in the vintages of Jukeboxes you expect to encounter
to make sure a tester you are thinking about buying will test them. The
most complete range might include sockets for 4 pin & 5 pin ( very old )
Octal, Loctal, 7 pin miniature, 9 pin miniature, and Compactron tubes such
as the 7868. There may be more socket types maybe someone else can add to
that. I seldom ever totally relied on a Tube Tester as a final decision to
replace a tube or not. If in doubt, replace the suspect tube with a known
good one or a new one. Many times rectifier tubes such as a 80, 5Y3 or
5U4 will show good in a tube tester but when installed in a power supply
such as in a Jukebox Amplifier they will not work. Another item to look for
is if the tube tester will test Thyratron Tubes such as the 2050 and 2D21
which were both used in Jukeboxes. An additional consideration to think
about is how do you know if the calibration of the metering circuits and the
meter itself are within the original manufacturers specifications ? This may
be a difficult thing to find out unless you can get the manufacturers
service information on the tester you buy. Some testers had service manuals
with them when new, others did not.

These are just some thoughts that popped into my mind about my experiences
with tube testers over many years. There are times when they are helpful and
there are times when they can give you a false reading. If you see
something available for little money such as at a tag sale or junk shop, if
you find you can not use it you shouldn't have a problem passing it on to
someone else.
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I was reading the other post about a tube tester. I need one also, but
after going through all the tube testers for sale on ebay.....I realized I
have no idea what to get. Some of them say they will check almost all TV
tubes, but does that also mean they will check Jukebox(radio) tubes as
well? What does mutual conductunce mean? Ive seen that on several of them.
Some seem to have only 4 or 5 holes to check tubes in, while others have
anywhere between 10 and 25 or more holes for tubes.How do I know what to
get that will check the tubes in my 1953 Seeburg and any future jukeboxes I
get? If any of you experts out there can shed some light on what I and
obviously some others here need to get, I would really appreciate it. Id
sure hate to buy one and find it does not have testing sockets for the
tubes I have. Thanks in advance for however can help me out with this,
because I know nothing about tubes at this point..........Mickey



 




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