[Hammarlund] Beware Russian 6SN7

[Bob Macklin]

If it's a metal tube isn't pin 1 suppose to be connected to the case? Does 
pin 1 on the socket have a good connation to ground?

Bob Macklin
K5MYJ
Seattle, Wa.
"Real Radios Glow In The Dark"
----- Original Message ----- 
From: "Carl" <km1h at jeremy.mv.com>
To: "Richard Knoppow" <1oldlens1 at ix.netcom.com>; 
<hammarlund at mailman.qth.net>
Sent: Thursday, December 09, 2010 6:21 PM
Subject: Re: [Hammarlund] Beware Russian 6SN7


> Did you check all the socket grounds, sounds like some corrosion under a 
> lug
> or three.
>
> Carl
> KM1H
>
>
> ----- Original Message ----- 
> From: "Richard Knoppow" <1oldlens1 at ix.netcom.com>
> To: <hammarlund at mailman.qth.net>
> Sent: Thursday, December 09, 2010 8:45 PM
> Subject: [Hammarlund] Beware Russian 6SN7
>
>
>>     The 6SN7 in my HQ-129-X measured weak on one side so I
>> got a couple of Russian made ones from my tube supplier to
>> replace it. They test fine in both my tube testers, an old
>> Weston and a TV-7B/U but both have 60hz hum. Note 60hz not
>> 120hz so its coming from the heaters somehow. I got another
>> 6SN7GTB today, this one made by General Electric, works fine
>> no hum. I don't know what the Russians are doing wrong but
>> there must be some heater to cathode leakage, both tubes
>> were identical.
>>     Another instance of a hummy tube was the 6K8 converter.
>> Hum modulation on the higher frequencies. I got two
>> replacements, I think both old RCA tubes, one a military
>> one. One has some hum, the other is perfectly clean. All
>> three test good on both testers.
>>     I checked the power supply before changing the tubes,
>> its almost ripple free. I think the new 6K8 may have
>> affected the frequency calibration but have not redone that
>> yet.
>>
>>
>> --
>> Richard Knoppow
>> Los Angeles
>> WB6KBL
>> dickburk at ix.netcom.com
>>
>>
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