Hi All!
I'm working on a Philco Model 46-420, I had a bad 50B5 along with some other tubes that needed replacing as well, I have gone completely through the radio, recapped etc... replaced all tubes as needed, the problem I have is both so called NOS 50B5's that I have bought have shown either shorts and or grid leakage on my tube tester, I can not fault the tester, for I have tested many many other tubes on this tester and it is accurate, my question is , was there an inherit problem with this particular tube, for I have yet too get a good one?
Mark

I have noticed the output tubes, like yours do seem wear out first, most of the time, but his is not the real problem, where you are buying the tubes is. No fair minded seller will put a shorted or shot tube on the market. Its your call but if you are willing to pay a fair price there are sellers that back what they sell 100% Consider what you spent on the duds and see if the cost of a guarenteed tube is worth it. There are some on EBAY, check out their statement and look for 100% positive feedback. Or try http://www.vacuumtubesinc.com/ or www.tubesandmore.com There are many more excelent sellers, Guys, a few more?

Hi Mark

A 50B5 runs hotter than most other tubes. It's not unusual to have some leakage between cathode & filament or even grid. As tubes have more use this leakage increases.

Does your tester have a neon lamp to show shorts? If the short lamp is only dim may not make a difference on a 50B5.

Since you bought NOS, number and brand marking should be easy to read. If they are missing tube may not be NOS?

In most radios you shouldn't need to be replace many tubes. Did you buy the radio from someone who just filled empty sockets with tubes?

Norm

:Hi All!
: I'm working on a Philco Model 46-420, I had a bad 50B5 along with some other tubes that needed replacing as well, I have gone completely through the radio, recapped etc... replaced all tubes as needed, the problem I have is both so called NOS 50B5's that I have bought have shown either shorts and or grid leakage on my tube tester, I can not fault the tester, for I have tested many many other tubes on this tester and it is accurate, my question is , was there an inherit problem with this particular tube, for I have yet too get a good one?
:Mark
:

:Hi Mark
:
: A 50B5 runs hotter than most other tubes. It's not unusual to have some leakage between cathode & filament or even grid. As tubes have more use this leakage increases.
:
: Does your tester have a neon lamp to show shorts? If the short lamp is only dim may not make a difference on a 50B5.
:
: Since you bought NOS, number and brand marking should be easy to read. If they are missing tube may not be NOS?
:
: In most radios you shouldn't need to be replace many tubes. Did you buy the radio from someone who just filled empty sockets with tubes?
:
:Norm
:
::Hi All!
:: I'm working on a Philco Model 46-420, I had a bad 50B5 along with some other tubes that needed replacing as well, I have gone completely through the radio, recapped etc... replaced all tubes as needed, the problem I have is both so called NOS 50B5's that I have bought have shown either shorts and or grid leakage on my tube tester, I can not fault the tester, for I have tested many many other tubes on this tester and it is accurate, my question is , was there an inherit problem with this particular tube, for I have yet too get a good one?
::Mark

Mark, I have several used 50B5's that I have no use for and would be happy to send you. They test good but the neon short indicator bulb on my tester is out. If you want them, email me your address. Regards,
Jon
::

::Hi Mark
::
:: A 50B5 runs hotter than most other tubes. It's not unusual to have some leakage between cathode & filament or even grid. As tubes have more use this leakage increases.
::
:: Does your tester have a neon lamp to show shorts? If the short lamp is only dim may not make a difference on a 50B5.
::
:: Since you bought NOS, number and brand marking should be easy to read. If they are missing tube may not be NOS?
::
:: In most radios you shouldn't need to be replace many tubes. Did you buy the radio from someone who just filled empty sockets with tubes?
::
::Norm
::
:::Hi All!
::: I'm working on a Philco Model 46-420, I had a bad 50B5 along with some other tubes that needed replacing as well, I have gone completely through the radio, recapped etc... replaced all tubes as needed, the problem I have is both so called NOS 50B5's that I have bought have shown either shorts and or grid leakage on my tube tester, I can not fault the tester, for I have tested many many other tubes on this tester and it is accurate, my question is , was there an inherit problem with this particular tube, for I have yet too get a good one?
:::Mark
:
:Mark, I have several used 50B5's that I have no use for and would be happy to send you. They test good but the neon short indicator bulb on my tester is out. If you want them, email me your address. Regards,
:Jon
:::Hi Jon!
Yes! if you have no use for them, I would gladly take them! let me know how much for the shipping costs, I will gladly pay for it, my address is:

Mark D. Moore
5404 S. 95th CT. #302
Omaha, NE 68127

Thanks Again Jon!
Mark

:::Hi Mark
:::
::: A 50B5 runs hotter than most other tubes. It's not unusual to have some leakage between cathode & filament or even grid. As tubes have more use this leakage increases.
:::
::: Does your tester have a neon lamp to show shorts? If the short lamp is only dim may not make a difference on a 50B5.
:::
::: Since you bought NOS, number and brand marking should be easy to read. If they are missing tube may not be NOS?
:::
::: In most radios you shouldn't need to be replace many tubes. Did you buy the radio from someone who just filled empty sockets with tubes?
:::
:::Norm
:::
::::Hi All!
:::: I'm working on a Philco Model 46-420, I had a bad 50B5 along with some other tubes that needed replacing as well, I have gone completely through the radio, recapped etc... replaced all tubes as needed, the problem I have is both so called NOS 50B5's that I have bought have shown either shorts and or grid leakage on my tube tester, I can not fault the tester, for I have tested many many other tubes on this tester and it is accurate, my question is , was there an inherit problem with this particular tube, for I have yet too get a good one?
::::Mark
::
::Mark, I have several used 50B5's that I have no use for and would be happy to send you. They test good but the neon short indicator bulb on my tester is out. If you want them, email me your address. Regards,
::Jon
::::Hi Jon!
: Yes! if you have no use for them, I would gladly take them! let me know how much for the shipping costs, I will gladly pay for it, my address is:
:
:
:Mark D. Moore
:5404 S. 95th CT. #302
:Omaha, NE 68127
:
: Thanks Again Jon!
:Mark

I will get them in the mail this weekend. Hope they work for you.
Jon.

:

::::Hi Mark
::::
:::: A 50B5 runs hotter than most other tubes. It's not unusual to have some leakage between cathode & filament or even grid. As tubes have more use this leakage increases.
::::
:::: Does your tester have a neon lamp to show shorts? If the short lamp is only dim may not make a difference on a 50B5.
::::
:::: Since you bought NOS, number and brand marking should be easy to read. If they are missing tube may not be NOS?
::::
:::: In most radios you shouldn't need to be replace many tubes. Did you buy the radio from someone who just filled empty sockets with tubes?
::::
::::Norm
::::
:::::Hi All!
::::: I'm working on a Philco Model 46-420, I had a bad 50B5 along with some other tubes that needed replacing as well, I have gone completely through the radio, recapped etc... replaced all tubes as needed, the problem I have is both so called NOS 50B5's that I have bought have shown either shorts and or grid leakage on my tube tester, I can not fault the tester, for I have tested many many other tubes on this tester and it is accurate, my question is , was there an inherit problem with this particular tube, for I have yet too get a good one?
:::::Mark
:::
:::Mark, I have several used 50B5's that I have no use for and would be happy to send you. They test good but the neon short indicator bulb on my tester is out. If you want them, email me your address. Regards,
:::Jon
:::::Hi Jon!
:: Yes! if you have no use for them, I would gladly take them! let me know how much for the shipping costs, I will gladly pay for it, my address is:
::
::
::Mark D. Moore
::5404 S. 95th CT. #302
::Omaha, NE 68127
::
:: Thanks Again Jon!
::Mark
:
:I will get them in the mail this weekend. Hope they work for you.
:Jon.
:
:Hi Jon!
Thank you so much! I really appreciate this, if I can be of service too you in the future just let me know.
Mark

::

:Hi Mark
:
: A 50B5 runs hotter than most other tubes. It's not unusual to have some leakage between cathode & filament or even grid. As tubes have more use this leakage increases.
:
: Does your tester have a neon lamp to show shorts? If the short lamp is only dim may not make a difference on a 50B5.
:
: Since you bought NOS, number and brand marking should be easy to read. If they are missing tube may not be NOS?
:
: In most radios you shouldn't need to be replace many tubes. Did you buy the radio from someone who just filled empty sockets with tubes?
:
:Norm
:
::Hi All!
:: I'm working on a Philco Model 46-420, I had a bad 50B5 along with some other tubes that needed replacing as well, I have gone completely through the radio, recapped etc... replaced all tubes as needed, the problem I have is both so called NOS 50B5's that I have bought have shown either shorts and or grid leakage on my tube tester, I can not fault the tester, for I have tested many many other tubes on this tester and it is accurate, my question is , was there an inherit problem with this particular tube, for I have yet too get a good one?
::Mark
::Hi Norm
Well, the short indicator is on steady and fairly well lit, in the past on other tubes it has proven them too be defective, I have gotten replacements for those tubes and tested again good, no indicator light, so I would say these 50B5's I've gotten are definitely bad.
Mark

50B5 tubes run rather hot and have the elements spaced rather closely. On my EICO 625, a strongly conducting tube may light one half of the neon glow bulb (one electrode vs. two). Lighting on one side means direct current--not a short. Sometimes they make both sides light dimly. This is a partial short...especially if it occurs after the tube has warmed up instead of when cold. What I have done is isolate the two elements. Say it's the control grid and the cathode. I throw the grid lever up and the cathode lever down. I leave all others in the middle. Then I turn the SELECTOR to #4, which is the highest current setting. Then, with the tube hot, I zap those elements a few times. Sparks may fly. I then test it again using normal settings (I also do element to element shorts tests to look for other shorts), and I thump the tube heavily with my fingers to make sure that a short can't vibrate into place. I have saved many a shorted tube including a 50C5, which is similar to your tube. The 50C5 I got right out of the box--unused, and it had a short between the cathode and control grid. In reality, of course, a short between the cathode and control grid can cause no harm other than audio trouble. If you are using an emissions tester, this is the only short you'd likely see, as all the grids and the plate are tied together, so you wouldn't see shorts between any of them without an element to element test....well, actually the beam grid is connected to the cathode, so you could get a short between the screen or plate and this grid. Your short is most likely between the control grid and the cathode, though.

Thomas

Regarding what I said about a typical neon shorts indicator, in many testers (especially emissions testers), the tube is fed alternating current. When the neon short indicator indicates a short, it will light on both sides (both electrodes will light). If a neon bulb is fed direct current, only one electrode will light up. This will change with polarity changes (I forgot which one lights for which polarity). The direct current flowing through a tube would normally light the neon light, but resistors and capacitors (varies by model) are arranged so that this current won't normally light the bulb. When a short occurs in a tube, a strong flow of alternating current is fed to the neon bulb, and lights it on both sides. Occasionally a tube conducts so well that its direct current also will light the neon bulb. The difference here is that the bulb will only light on one side, and usually rather dimly.

Thomas