[ARC5] Glass or Metal Tubes Preferred for Receivers

[Rich Post]

I ran into the "hot" tube issue when looking over a newly acquired
Hallicrafters S-76. I noticed a tube substitution. The 5Y3 rectifier had
been replaced by a 5Z4, a metal tube. That was a reasonable substitution
voltage and current-wise,.. but wait. A metal tube connects pin 1 to its
metal shell. A quick check showed that Hallicrafters had used pin 1 of the
rectifier socket as a B+ tie point. Therefore the tube shell would be live
with B+, a "gotcha" just waiting for the unwary. I quickly located a proper
glass 5Y3GT.

Rich KB8TAD

On Mon, Feb 5, 2018 at 4:56 PM, Richard Knoppow <1oldlens1 at ix.netcom.com>
wrote:

>    I wonder how this happened. T
>
>> 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
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