[Amps] Glass melting, f, and D-factor

[R L Measures]

On Jul 31, 2006, at 10:16 AM, Steve Thompson wrote:

>
>
> R L Measures wrote:
>> It was previously stated by another denizen that the glass in early
>> Chinese 3-500Zs was melting on the sides, however, according to my
>> notes from Rus Healy, in this case, the glass reportedly softened on
>> the top in an area a couple of cm from the anode stem, a small bubble
>> formed, began expanding inward from atmospheric pressure, and popped.
>> end
> For clarity - what Rus reported happened to what model of tube made  
> by who?

A 3-500Z prototype made by Paul Hrivnak in Canada.

> Did Rus see it himself?

   Paul telephoned Russ at Newington and described the bubbling  
phenomenon.
Since Russ owned an amplifier that had been damaged in a strange way  
by VHF parasitics, he told Paul that this might be the cause.   
Subsequently, Russ telephoned me and described what had happened to  
the glass.  A few momths later we, discussed the event at length over  
pizza in Camarillo, CA.

> Was it a one off or reliably repeatable?

It apparently happened in a prototype amplifier. My guess is that the  
Chinese quickly realized the problem with lead-fluxed glass at VHF  
and switched to a borosilicate glass.

>
> Thanks,
>
> Steve
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R L MEASURES, AG6K. 805-386-3734
r at somis.org