[Hammarlund] Beware Russian 6SN7

[Carl]

There are no metal 6SN7's

Carl
KM1H


----- Original Message ----- 
From: "Bob Macklin" <macklinbob at msn.com>
To: "Carl" <km1h at jeremy.mv.com>; "Richard Knoppow" 
<1oldlens1 at ix.netcom.com>; <hammarlund at mailman.qth.net>
Sent: Thursday, December 09, 2010 9:57 PM
Subject: Re: [Hammarlund] Beware Russian 6SN7


> 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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>