[AMPS] Re: Opening tubes for inspection

[Rich Measures]

>Rich,
>
>How do you open the ceramic seal tubes to inspect them when they are dead ? 

€  I clamp the anode of the kaput tube in a vise, with the base sticking 
out horizontally.  Using a fine-tooth sheet-metal cutting coping-saw 
blade, I saw through the sheet metal just above the anode-grid insulator 
(close to the cooling fins inlet).  The metal is about a mm thick.  There 
is a danger of sawing too deeply and ruining the grid, so the tube must 
be rotated in c. 5 deg. increments as the sawing progresses.  Slowly is 
better than faster.  //  I have heard that a lathe can be used to remove 
the anode.  

>Have a couple of interesting ones laying on the shelf...
>
€  If you have access to a high potential breakdown tester, it might be 
interesting to firstly see what the breakdown voltage is between the 
anode and grid, with positive polarity, and with negative polarity.  
Uniform leakage indicates gas in the envelope.  More leakage with 
positive polarity than with negative polarity indicates sputtered gold.   

€  In order to see gold melt-balls one needs a 30-x or so microscope.  

-  good luck, Peter


>
>
>> Contrary to innuendo noted on this reflector some weeks ago, 
>>I've never seen "gold balls" in any power tube used in any ALPHA or ETO 
>>medical or industrial amplifier - not an 8874, 8877, 3CX800A7, 3CPX5000A7, 
>> 4CX800A or other tube. 
>€ If one opens leaky tubes to see what's what, the warranty is voided. 
>> Neither I nor any other ETO/ALPHA employee so far 
>>as I know has ever learned of any such event from any credible source, 
>€ There are some photographs of gold sputtered tubes in the September 
>1990 issue of *QST*. 
>



Rich...

R. L. Measures, 805-386-3734, AG6K, www.vcnet.com/measures  


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