How to recognize tube without any printing

How to recognize tube without any printing

Post by Bonz » Sun, 27 Jan 2013 06:41:22



Good evening to everybody.
I'm new to this group and I hope you can help me.
I was given more than 200 tubes, most of of them with rubbed off printings, and I cannot identifying them.
Moreover most of them are tv-type tubes with similar form (pcl82, pcl86 ecc...).

Is there a way (or an instrument) to identifying them?

Thank you in advice for your time!

 
 
 

How to recognize tube without any printing

Post by Jim Muelle » Sun, 27 Jan 2013 07:24:00


Quote:

> Good evening to everybody.
> I'm new to this group and I hope you can help me.
> I was given more than 200 tubes, most of of them with rubbed off
> printings, and I cannot identifying them.
> Moreover most of them are tv-type tubes with similar form (pcl82, pcl86
> ecc...).

> Is there a way (or an instrument) to identifying them?

> Thank you in advice for your time!

First, be sure to look everywhere on the tube.  Octal and older tubes
tend to have the number in the middle of the side or on the top,
sometimes on the base.  Miniature tubes can have the number almost
anywhere, even printed in a circle around the exhaust tip.  Metal tubes
sometimes have the number stamped into the side of the base.

There are a number of techniques that work on American made tubes.  Try
using a flashlight and looking/shining at different angles.  If the
elements are light colored, see if the number will cast a shadow that can
be read.  If there is nothing in the way, try looking through the tube to
read the number from the back side.  Exhale through your mouth on the
tube and examine it with a flashlight before the moisture evaporates.  
Put the tube in a freezer and see if ice or condensation will bring out
the number.  Rub your finger on the side of your nose to pick up some
oil.  Rub this over the number and then try a flashlight.  You may have
to rub in different directions as well as shine the light from various
angles.

I have used all of these methods except the freezer and one or another
works most of the time.  However, there are still a few that won't
respond to any of these techniques.  Don't expect the number to look like
new.  It will usually be very faint and require careful examination to
read it; a darkened room may be helpful.  When you find the number, mark
it on the tube with a Sharpie or some other method so you won't have to
go through this again.

European manufacturers used a different ink than American manufacturers.  
It disappears quite easily so I wouldn't recommend any method that
involves water or rubbing.  I don't have enough with missing numbers to
recommend a method for these.  Some of these tubes have a code number
near the base that can be used to identify them.  I don't know the
details of these codes so you need to Google it.

Japanese manufacturers used a number of types of marking so you will have
to take a guess with these.

American tubes usually have smooth envelopes.  European tubes usually
have mold separation marks in the glass.  Japanese tubes show up both
ways.

Good luck,

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How to recognize tube without any printing

Post by John Robertso » Sun, 27 Jan 2013 15:49:19


Quote:


>> Good evening to everybody.
>> I'm new to this group and I hope you can help me.
>> I was given more than 200 tubes, most of of them with rubbed off
>> printings, and I cannot identifying them.
>> Moreover most of them are tv-type tubes with similar form (pcl82, pcl86
>> ecc...).

>> Is there a way (or an instrument) to identifying them?

>> Thank you in advice for your time!

> First, be sure to look everywhere on the tube.  Octal and older tubes
> tend to have the number in the middle of the side or on the top,
> sometimes on the base.  Miniature tubes can have the number almost
> anywhere, even printed in a circle around the exhaust tip.  Metal tubes
> sometimes have the number stamped into the side of the base.

> There are a number of techniques that work on American made tubes.  Try
> using a flashlight and looking/shining at different angles.  If the
> elements are light colored, see if the number will cast a shadow that can
> be read.  If there is nothing in the way, try looking through the tube to
> read the number from the back side.  Exhale through your mouth on the
> tube and examine it with a flashlight before the moisture evaporates.  
> Put the tube in a freezer and see if ice or condensation will bring out
> the number.  Rub your finger on the side of your nose to pick up some
> oil.  Rub this over the number and then try a flashlight.  You may have
> to rub in different directions as well as shine the light from various
> angles.

> I have used all of these methods except the freezer and one or another
> works most of the time.  However, there are still a few that won't
> respond to any of these techniques.  Don't expect the number to look like
> new.  It will usually be very faint and require careful examination to
> read it; a darkened room may be helpful.  When you find the number, mark
> it on the tube with a Sharpie or some other method so you won't have to
> go through this again.

> European manufacturers used a different ink than American manufacturers.  
> It disappears quite easily so I wouldn't recommend any method that
> involves water or rubbing.  I don't have enough with missing numbers to
> recommend a method for these.  Some of these tubes have a code number
> near the base that can be used to identify them.  I don't know the
> details of these codes so you need to Google it.

> Japanese manufacturers used a number of types of marking so you will have
> to take a guess with these.

> American tubes usually have smooth envelopes.  European tubes usually
> have mold separation marks in the glass.  Japanese tubes show up both
> ways.

> Good luck,

As Jim says, these are the ways most of us use to try and figure out
what the tube is. You can also visually match the tubes against each
other if you have any with marks and others that look identical they may
well be the same. You have to look at the connections inside the tube,
the style of the plate and insulators etc. Then if you think you have a
tube that matches a known tube number check the cold resistance of the
filament with your ohm-meter. Should be very close.

If not sure then try testing the unknown tube at 6.3V if the one you
think it matches is a 12.6V tube.

Another test is to identify the filament leads and slowly dial up the
voltage until the filament glows about right (dull orange to light red)
and see what the voltage is.

Pity most of the tubes have little if any value unless they are very old
style so you have to decide if your time is worth it.

There is no automatic tube identification tester that I've ever heard of
- could be designed and built, but it would be pricey!

John :-#)#
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