[ARC5] Glass or Metal Tubes Preferred for Receivers

[Richard Knoppow]

    I wonder how this happened. The shell of metal 
tubes normally goes to pin-1 which is grounded. 
Some glass tubes have an internal shield to pin-1. 
It sounds like the pin was shorted to something.
    I have a BC-779 Super-Pro which I have had for 
a great many years and never had anything like 
this happen. OTOH, I have gotten bites from metal 
tubes on some other receivers, I think due to cold 
solder joints.
    Something else: The 6SB7Y is a high 
performance mixer tube. For some reason it was 
never available as a metal tube. It was designed 
for FM radios but not used much. Perhaps for use 
in the vicinity of 100 MHz the metal envelope is 
inferior.  The 6BA7 has nearly identical 
characteristics.

On 2/5/2018 1:40 PM, Phillip Carpenter wrote:
> If it’s not hot the filament is dead.
> 
> Sent from my iPhone
> 
> On Feb 5, 2018, at 11:16 AM, Robert Eleazer 
> <releazer at earthlink.net 
> <mailto:releazer at earthlink.net>> wrote:
> 
>> The problem with metal tubes is that you can't 
>> see the pilot light.
>> And if instead you grab it to see if is warm 
>> then you risk electrocution.  I can recall a 
>> shocking experience with a Super Pro, which I 
>> subsequently gave away.
>>
>> Wayne
>> WB5WSV


-- 
Richard Knoppow
1oldlens1 at ix.netcom.com
WB6KBL